-< Ecological Effects of the WICKERSHAM DOME · The Wickersham Dome fire occurred in late June 1971...

GENERAL TECHNICAL R E P O R T PNW-90 - - . - JULY 1979

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Ecological Effects of the WICKERSHAM DOME ~ Near Fairbanks. Alaska

AND RANGE EXPERlMENT STATION 1 . B U R € . , F D R E S T SERVI-CF

General Technical Report PNW-90 1979

ECOLOGICAL EFFECTS OF THE WICKERSHAM DOME FIRE

NEAR FAIRBANKS. ALASKA

L. A. Viereck Technical Editors C. T. Dyrness

Pacific Northwest Forest and Range Experiment Station Forest Service U.S. Department of Agriculture

Portland, Oregon

The Wickersham Dome fire occurred in late June 1971 and burned over 6 300 hectares of predominantly black spruce forest land. Shortly after the fire was controlled, studies of the effects of the fire on various components of the biotic community were under- taken. Results reported here are mainly for the first 3 years after the fire.

KEYWORDS: Fire effects, fire (-hydrology, soil properties (chemical), succession, fire (-regeneration, black spruce, Picea mariana, quaking aspen (~opulus tremuloides), Alaska (Wickersham Dome).

Examination of soil after the fire disclosed that moist, lower layers of the forest floor had minimized the impact of the fire on the soil. Burning reduced the thickness of the forest floor layer an average of 10.3 centimeters in heavily burned areas and 5.7 centimeters in lightly burned areas in a study location where the thickness averaged 28.7 centimeters in unburned areas. Burn- ing did not have a measurable effect on the chemical properties of the underlying mineral soil. The reduction of forest floor thickness and the blackened surface resulted in higher soil temperatures. These higher temperatures caused a substantial retreat of the permafrost layer in burned areas. Depth to permafrost averaged 84 centimeters for burned areas and 47 centimeters for the unburned control 3 years after the fire.

Development of vegetation after the fire was closely tied to severity of the fire. On one lightly burned black spruce site, Ilve ground vegetation cover still totaled 40 percent after the fire and included considerable amounts of mosses and CZadonia lichens. Vegetative cover at this location had increased to 70 percent 3 years after the fire. In contrast, recovery of vegetation in heavily burned black spruce stands was much slower. No mosses or lichens survived the fire, and most early cover was contributed by such herbaceous species as horsetail (Equisetum sylvaticum) and fireweed (~pilobium angustifolium). Few invading species appeared after the fire; most postfire cover was contributed by residual species which reproduced vegetatively. Biomass production was extremely variable over the burned area and, at the end of the 3d year, ranged from 33 grams per square meter in a heavily burned black spruce stand to 804 grams per square meter (mostly aspen sprouts) in a heavily burned aspen stand. Studies of leaves and needles in litterbags indicated that rates of decomposition were the same in burned and unburned stands. The 1st year after the fire, black spruce seed fall in the burned plots was almost four times as great as that in the unburned control. The germination capacity of black spruce seed was low in heavily burned areas and tended to decrease with time. On burned plots, only 1 percent of germinable seeds actually developed into established seedlings.

Studies of animals after the fire focused on arthropods, microtine rodents, and snowshoe hares (Lepus americanus). Numbers of spiders, Collembola, mites, Coleoptera, and other arthropods were higher in the burned area than in the unburned control. Numbers of northern red-backed voles (CZethrionomys rutilus) were substantially reduced after the fire, and the voles did not overwinter in the burned area until 3 years after the fire. The tundra vole (~icrotus oeconomus), although rare in unburned black spruce stands, also established a resident population in the burned area 3 years after the fire. Because snowshoe hares were at a very high population level, they consumed large quantities of willow sprouts and charred bark during the fall and winter after the fire. Hare population levels stayed high until 1974, when they dropped precipitously. During the study period, the snowshoe hare population varied from a high of six hares per hectare in the fall of 1971 to a low of 0.12 hare per hectare in the spring of 1975.

CONTENTS

Page

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 1

DESCRIPTION OF STUDY AREA . . . . . . . . . . . . . . . . . 2

SELECTION OF STUDY PLOTS . . . . . . . . . . . . . . . . . 5

ABIOTIC FACTORS . . . . . . . . . . . . . . . . . . . . . . 8 The S o i l . . . . . . . . . . . . . . . . . . . . . . . . 8

General d e s c r i p t i o n of s o i l s i n t h e s t u d y a r e a . . . 8 E f f e c t s of burning on f o r e s t f l o o r c h a r a c t e r i s t i c s . 1 0

. . . Mineral s o i l c h a r a c t e r i s t i c s fo l lowing burning 1 2 . . . . . . . . E f f e c t of burning on s o i l temperature 1 4

. . . . . . . . . . . . . . . . . . . . . Permafros t 1 7 C l i m a t i c F a c t o r s . . . . . . . . . . . . . . . . . . . . 2 1

. . . . . Snow depths i n burned and unburned f o r e s t s 2 1 . . . . . . . . . . . . . . . . . . . A i r t e m p e r a t u r e 23 . . . . . . . . . . . . . . . . . . Stream Water Q u a l i t y 2 4

. . . . . . . . . . . . . . . . . . . . . . BIOTICFACTORS 25 . . . . . . . . . . . . . . . . . . V e g e t a t i o n A n a l y s i s 25

. . . . . . . . . . . . . . . . . . . . . . . . Biomass 34 L i t t e r F a l l . . . . . . . . . . . . . . . . . . . . . . 39

. . . . . . . . . . . . . . . . . . L i t t e r Decomposition 41 . . . Black Spruce Seed F a l l and .Seed l ing Establ ishment 42

Quan t i ty and q u a l i t y of d i s p e r s e d seed . . . . . . . 45 . . . . . . . . . . Annual p a t t e r n of seed d i s p e r s a l 46

. . . Autecology of 1st Year P o s t f i r e Tree Regenera t ion 50 . . . . . . . E f f e c t s of F i r e on Arthropod D i s t r i b u t i o n 53

. . . . Numeric Response of Micro t ine Rodents A f t e r F i r e 55 H a b i t a t U t i l i z a t i o n by Snowshoe Hares i n Burned and

Unburned Black Spruce Communities . . . . . . . . . . 57

. . . . . . . . . . . . . . . . . . . . . . . . . . SUMMARY 63

LITERATURECITED . . . . . . . . . . . . . . . . . . . . . 68

In interior Alaska, fire is an extremely important environmental factor. The varied array of forest communities--with paper birch (BetuZa papyrifera Marsh. ) , aspen (PopuZus tremuzoides Michx.), black spruce (Picea mariana (Mill.) B.S.P.), and white spruce (~icea glauca (Moench) Voss) as principal tree components-- displays patterns over the landscape which, in almost every case, can be directly traced to the distribution of past fires. Also, as a result of repeated wildfires, stands of trees older than 170 years are rare, except on islands in major rivers, throughout most of the Alaska interior. Wildfire statistics indicate that over the past 30 years about 400 000 ha a year were burned (Barney 1971).

Early interest in Alaska wildfires concentrated mainly on investigating means of improving fire control technology. Begin- ning about 1970, however, increasing numbers of individuals and Alaska groups began to propose that wildfires might be beneficial in some cases. Some suggested that since wildfires started by lightning are a normal part of the taiga environment, areas should be designated where wildfires are allowed to burn and natural processes permitted to continue as in the past. Proponents argued that such a policy would reduce fire control costs, lessen environmental degradation caused by fire suppression activities, and increase the acreage of sera1 plant communities important to herbivores, such as moose. Choice of optimum fire management strategies for interior Alaska cannot be made, however, without sufficient quantitative information on the effects of wildfires on taiga ecosystems. Because this necessary information is not available, scientists at the Institute of Northern Forestry are attempting to gain a better understanding of the role of fire in the distribution, structure, and function of taiga ecosystems.

An important part of this effort has been intensive study of an area on Wickersham Dome burned over by a 1971 wildfire. A multidisciplinary study was initiated soon after the fire was controlled, in an attempt to assess the impact of the fire on biotic communities and their environments. Scientists represent- ing several disciplines directed their talents to the study of as many abiotic and biotic factors as possible. The most intensive portion of this study extended through 1973, although certain portions of the study are still continuing.

his section was prepared by C. T. Dyrness, Supervisory Soil Scientist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

DESCRIPTION OF STUDY AREA2 The Wickersham Dome research area is located about 50 km north-

west of Fairbanks, adjacent to the Elliott Highway (fig. 1). It is situated within the Yukon-Tanana Uplands physiographic province, an area of relatively gentle relief with rounded ridges oriented in a northeast-southwest direction. Elevations range from 210 m at the lowest level along Washington Creek to 980 m at the summit of Wickersham Dome. The area lies within the boundaries of the Pipeline Corridor Reserve designated by the Bureau of Land Manage- ment, U.S. Department of the Interior.

Figure 1 . - - l o c a t i o n o f Wickersham Dome fire and sampled s t a n d s .

2 ~ e s c r i p t i o n prepared by C . T . Dyrness, Supervisory So i l S c i e n t i s t , USDA Forest Service, Pac i f i c Northwest Forest and Range Experiment S ta t ion , I n s t i - t u t e of Northern Forestry, Fairbanks, Alaska.

Geologically, the area is characterized by Precambrian schist and gneiss bedrock which has not been modified by glaciation. Except at highest elevations, bedrock is mantled by a layer of wind-deposited loess. The study area lies within the zone of discontinuous permafrost. Ridgetops and upper south slopes tend to be free of permafrost. In other locations, however, permafrost is generally about 40 to 50 cm below the surface. Mineral soils are silt loam in texture and are mantled by organic materials (mostly mosses and litter) approximately 20 to 50 cm thick.

Before the 1971 wildfire, the area was mainly covered with black spruce stands, ranging in age from 50 to 125 years, depending on fire history. Stands were open, dominated by slow-growing black spruce 6-10 m in height and 8-12 cm in diameter, and inter- spersed with occasional paper birch and scattered large willow (mostly SaZix scouZeriana Barratt) and alder (~Znus crispa (Ait . ) Pursh) shrubs. The most conspicuous vascular plants in the understory were low shrubs, such as Labrador-tea (Ledum groen- Zandicum Oeder), bog blueberry (Vaccinium uZiginosum L.), mountain- cranberry (Vaccinium vitis-idaea L.), and prickly rose (Rosa acicuZaris Lindl.). A nearly continuous moss cover was present, made up of feather mosses, with some Sphagnum. Lichens were also conspicuous components of the ground cover, primarily CZadonia and Pettigera species. Stands of quaking aspen occurred on some slopes and were characterized by a striking decrease in moss cover in the understory.

The fire, ignited by lightning on June 24, 1971, started near Wickersham Dome. Bureau of Land Management personnel made an all-out effort to control the fire--775 people, 29 bulldozers, 6 pumps, 4 tankers, and 4 helicopters--but the fire proved diffi- cult to control because of low fuel moisture and generally brisk breezes. The fire burned in a southwesterly direction and was finally stopped on June 30, but only after 242 000 liters of retardant had been aerially dropped. General outline of the burned area is shown in figure 1.

Burned area totaled 6 313 ha, of which 5 100 ha were Federal and 1 213 ha were State or privately owned. Expenditures for control totaled $1,099,479; damages to timber, recreation, soil, grazing, and wildlife resources were estimated at $655,200 (Noste and Davis 1975).

Weather conditions at the time of ignition on June 24 were conducive to fast rates of fire spread, contributing to the failure of initial attack. The maximum reported temperature of 300C, combined with a calculated 2.5-percent fine fuel moisture and 6 m/s wind, yields a spread index of 70 (table 1)--a value exceeded less than 1 percent of the time, based on Fairbanks records (Barney 1967). Conditions on June 25 and 26 had a similarly high potential for fire, except the wind was much lower-- only 3 m/s. The spread index was 43 and 42 on June 25 and 26; these are exceeded only about 20 percent of the time. On June 27, windspeed increased again, yielding a spread index of 58, a value exceeded less than 5 percent of the time. By this time the head of the fire had reached a ridgetop between Washington Creek and

Table 1--Weather conditions at Fairbanks during the Wickersham Dome fire, 1971

OF - - - -Percent- - - Miles Der hour

t h e Cha tan ika R i v e r , and t h e r a t e s of s p r e a d d e c r e a s e d s u b s t a n - t i a l l y . The days on which t h e f i r e bu rned , b e i n g s o n e a r t h e summer s o l s t i c e , had v e r y s h o r t n i g h t s w i t h l i t t l e t ime f o r r e c o v e r y o f m o i s t u r e i n t h e f i n e f u e l s .

June

The b u i l d u p i n d e x , a measure of m o i s t u r e c o n t e n t i n t h e h e a v i e r f u e l s , i s a r e l a t i v e i n d i c a t o r of t h e p o t e n t i a l i n t e n s i t y of t h e f i r e . H i s t o r i c a l l y , v a l u e s o f 128 a r e exceeded abou t 3 p e r c e n t o f t h e t ime d u r i n g t h e f i r e s e a s o n i n t h e f i r e a r e a . Burning c o n d i t i o n s , a s i n d i c a t e d by t h e s p r e a d and b u i l d u p i n d e x e s , were q u i t e s e v e r e a t t h e t ime o f i g n i t i o n and d u r i n g t h e major p a r t of t h e t ime t h e f i r e was s p r e a d i n g .

Spread index

B u l l d o z e r s c o n s t r u c t e d abou t 113 km o f f i r e l i n e which averaged 1 2 m i n w i d t h . Because much o f t h e a r e a i s u n d e r l a i n by perma- f r o s t , e r o s i o n was r a p i d when t h e i n s u l a t i n g mat of o r g a n i c m a t e r i a l s was removed. Soon a f t e r t h e f i r e , i t was e s t i m a t e d t h a t a t l e a s t 75 p e r c e n t o f d o z e r - c o n s t r u c t e d f i r e l i n e s needed r e h a b i l i t a t i o n t o p r e v e n t o r s low e r o s i o n . By J u l y 4 , 1971, m e l t i n g o f exposed p e r m a f r o s t had proceeded t o such an e x t e n t t h a t i t was c a u s i n g c o n s i d e r a b l e e r o s i o n and s i l t a t i o n of Washing- t o n Creek. T h e r e f o r e , an e x t e n s i v e program o f t r a c t o r - c o n s t r u c t i o n o f w a t e r b a r s and d i v e r s i o n d i t c h e s on f i r e l i n e s was begun immedi- a t e l y . I n a d d i t i o n , d u r i n g t h e f o l l o w i n g A p r i l (1972) , f i r e b r e a k s were a e r i a l l y sown w i t h g r a s s and f e r t i l i z e d . The s e e d mix tu re c o n s i s t e d o f Manchar smooth brome (37 .5 p e r c e n t ) , c r e e p i n g r e d f e s c u e (37 .5 p e r c e n t ) , and Rodney o a t s (25 p e r c e n t ) , a p p l i e d a t a a r a t e o f 45 kg/ha . Also a e r i a l l y a p p l i e d were 336 kg/ha o f p e l l e t e d 10-20-20 f e r t i l i z e r .

Buildup index Direction Maximum

temperature Relative humidity

Fine fuel moisture Windspeed

SELECTION STUDY I n August 1971, we s e l e c t e d s i t e s f o r i n t e n s i v e s t u d y of t h e

e f f e c t s o f f i r e i n b l a c k s p r u c e s t a n d s . We i n t e n d e d t o s e c u r e t h r e e s e t s o f p l o t s , each c o n t a i n i n g t h r e e p l o t s - - a n unburned s t a n d ( c o n t r o l - - c a l l e d t h e unburned c o n t r o l ) , a l i g h t l y burned s t a n d , and a h e a v i l y burned s t a n d ; however, f o r one s e t of p l o t s , o n l y a h e a v i l y burned s t a n d was a v a i l a b l e b e s i d e s t h e unburned c o n t r o l .

C r i t e r i a used f o r e v a l u a t i o n o f t h e i n t e n s i t y o f t h e bu rn were :

L i g h t l y b u r n e d - - l e s s t h a n 50 p e r c e n t o f t h e ground s u r f a c e b l a c k e n e d ; l e s s e r v e g e t a t i o n n o t consumed; b r a n c h l e t s p r e s e n t on t r e e s and crowns s c o r c h e d b u t n o t consumed.

Heav i ly burned--more t h a n 90-95 p e r c e n t o f t h e a r e a b l a c k e n e d ; l e s s e r v e g e t a t i o n and t r e e crowns consumed.

We d i d n o t a t t e m p t t o e v a l u a t e s t a n d s w i t h 50-90 p e r c e n t of t h e a r e a b l ackened .

The t h r e e s e t s o f p l o t s s e l e c t e d were a l o n g a g e n e r a l l y e a s t - wes t t r a n s e c t a c r o s s t h e burned a r e a . A l l were i n a r e a s o f b l a c k s p r u c e . P l o t s e t 1 was l o c a t e d between 335 and 396 m i n e l e v a - t i o n . T h i s s e t o f p l o t s was on a w e s t - f a c i n g s l o p e w i t h a g r a d i e n t o f 12 -20 p e r c e n t and c o n s i s t e d o f a n unburned c o n t r o l p l u s a l i g h t l y burned and a h e a v i l y burned s t a n d . P l o t s e t 2 , c o n s i s t i n g of a n unburned c o n t r o l and a l i g h t l y burned and a h e a v i l y burned s t a n d , was l o c a t e d a t approx ima te ly 335-m e l e v a t i o n on a g e n t l e , e a s t - f a c i n g s l o p e . P l o t s e t 3 was l o c a t e d a t an e l e v a t i o n of a p p r o x i - ma te ly 468 m on t h e n e a r l y f l a t c r e s t of a r i d g e ; s l o p e s , having a g e n e r a l l y w e s t e r n a s p e c t , were 0 t o 5 p e r c e n t . P l o t s e t 3 con- s i s t e d o f o n l y two s t a n d s , an unburned c o n t r o l and a h e a v i l y burned s t a n d . Examples o f t h e t h r e e c o n d i t i o n s a r e shown i n f i g u r e s 2 , 3 , and 4 .

During t h e summer o f 1972, t h r e e a d d i t i o n a l p l o t s were e s t a b - l i s h e d . A s e t o f two p l o t s ( p l o t s e t 4 ) - - o n e h e a v i l y burned ( f i g . 5) and t h e o t h e r an unburned c o n t r o l - - w a s l o c a t e d i n an a r e a o f a spen a t an e l e v a t i o n of approx ima te ly 510 m a t a mids lope p o s i t i o n ; s l o p e s were 13-15 p e r c e n t , and a s p e c t was dominant ly s o u t h . I n a d d i t i o n , a n o t h e r unburned s t a n d , s i t u a t e d on a lower p o r t i o n of t h e s l o p e ( a t an e l e v a t i o n of 335 m), was added t o p l o t s e t 1 a s a c o n t r o l f o r t h e nea rby h e a v i l y burned p l o t . C h a r a c t e r i s t i c s o f a l l t h e p l o t s a r e summarized i n t a b l e 2 .

3 ~ h i s s e c t i o n was prepared by C . T. Dyrness, Supervisory S o i l S c i e n t i s t , USDA Fores t Serv ice , P a c i f i c Northwest Forest and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

F i g u r e 2 . --General v i e w o f unburned b l a c k s p r u c e s t a n d .

F igure 3. - -Light1 y burned s tand (BS-IL) , showing t y p i c a l ground c o v e r remain ing a f t e r the f i r e .

Figure 4 .--General c o n d i t i o n o f h e a v i l y burned s t a n d s i s shown here b y s tand BS-3H. L i g h t c o l o r i n background i s unburned b u t k i l l e d Sphagnum moss mound.

F i g u r e 5 . --View o f burned a s p e n s t a n d i n August 1972 (AS-IB) shows devel opment o f a spen s u c k e r s h o o t s . No te how snowshoe h a r e s removed the charred b a r k dur- i n g the 1971 -72 w i n t e r .

Table 2--Physical description and burn intensity of 11 stands after the Wickersham Dome fire

Percent

Ides t West

West Southwest

Southeast East East

Level West

Southwest South

Year of establishment

'lot set

Meters

396 396

335 335

335 335 335

4 68 468

518 503

Middle Middle

Lower Lower

Lower Lower Lower

Ridgetop Ridgetop

Middle Middle

Control Light

Heavy Control

Control Light Heavy

Control Heavy

Control Heavy

Stand

ABIOTIC

Slope

FACTORS

Aspect

The Soil

Slope position Elevation

General description of soils in the study area4

Burn intensity

Soils in the Wickersham Dome area are formed in a layer of wind-deposited silty materials (loess) over weathered mica schist bedrock of the Birch Creek formation. The loess mantle varies in thickness from a few centimeters on steep slopes and ridgetops to over a meter on lower slopes and valley bottoms. Since this is an area of discontinuous permafrost, soils frequently lack permafrost on ridgetops and south-facing slopes, but shallow permafrost is present in soils on north-facing slopes and valley bottoms. Soils .with a shallow permafrost table are marked by deep (up to 50-cm), overlying layers of moss and litter and a continuously wet profile throughout the growing season.

During the summer of 1974, C. E. Furbush and D. B. Schoephorster, soil scientists with the U.S.D.A. Soil Conservation Service, mapped the soils over most of the fire area. They identified five soil series in the area--Ester, Fairplay, Gilmore, Goldstream, and Saulich. The Ester, Fairplay, and Saulich series occur in the plot areas and therefore we will describe them in some detail.

4~escription piepared by C. T. Dyrness, Supervisory Soil Scientist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Insti- tute of Northern Forestry, Fairbanks, Alaska.

The Gilmore s e r i e s i s r e s t r i c t e d t o upper s l o p e s and r i d g e t o p s and c o n s i s t s o f w e l l - d r a i n e d , p e r m a f r o s t - f r e e s o i l s formed i n a s h a l l o w l o e s s man t l e o v e r g r a v e l l y s i l t loam d e r i v e d from t h e u n d e r l y i n g wea the red s c h i s t . S o i l s c l a s s i f i e d i n t h e Goldstream s e r i e s a r e p o o r l y d r a i n e d , s i l t y s o i l s t h a t occur i n v a l l e y bo t toms . These s o i l s t y p i c a l l y have a s h a l l o w p e r m a f r o s t t a b l e and a r e t h e r e f o r e wet t h roughou t t h e summer.

According t o r e s u l t s o f t h e s o i l s u r v e y , p l o t s making up p l o t s e t 1 a r e s i t u a t e d on two s o i l s e r i e s - - t h e E s t e r and t h e S a u l i c h . F o r t u n a t e l y , each s o i l h a s b o t h a burned s t a n d and an unburned c o n t r o l .

One unburned c o n t r o l and a l i g h t l y burned s t a n d a r e i n an a r e a of E s t e r s i l t loam, a p o o r l y d r a i n e d s o i l t h a t o c c u r s on n o r t h - f a c i n g s l o p e s . These s o i l s a r e g e n e r a l l y s h a l l o w t o b o t h perma- f r o s t and bedrock ( s i l t man t l e i s g e n e r a l l y l e s s t h a n 50 cm t h i c k ) . E s t e r s o i l s t y p i c a l l y have a t h i c k moss and l i t t e r s u r f a c e l a y e r o v e r m o t t l e d d a r k grayish-brown s i l t loam o r g r a v e l l y s i l t loam; amounts o f g r a v e l i n c r e a s e w i t h d e p t h . The p e r m a f r o s t t a b l e i s g e n e r a l l y w i t h i n 25 cm o f t h e s u r f a c e of t h e m i n e r a l s o i l , and t h e s o i l above t h e f r o s t l i n e i s i n v a r i a b l y we t . Where bedrock i s s h a l l o w o r t h e s u r f a c e o r g a n i c l a y e r i s t h i n , p e r m a f r o s t may be l a c k i n g above t h e r o c k .

The h e a v i l y burned s t a n d and t h e unburned c o n t r o l i n p l o t s e t 1 a r e s i t u a t e d on S a u l i c h s i l t loam s o i l s which , i n many r e s p e c t s , resemble E s t e r s o i l s b u t a r e formed i n deepe r l o e s s d e p o s i t s on lower s l o p e s . S a u l i c h s o i l s a r e p o o r l y d r a i n e d , have s h a l l o w p e r m a f r o s t l a y e r s , and a r e g e n e r a l l y v e r y m o i s t t o wet . They a r e formed i n s i l t loam d e p o s i t s more t h a n 75 cm t h i c k . A t y p i c a l S a u l i c h p r o f i l e h a s a m o s s - l i t t e r l a y e r 25-30 cm t h i c k , u n d e r l a i n by 1 0 cm o f very t h i c k , v e r y d a r k g ray i sh -b rown s i l t loam A 1 h o r i z o n , ove r a f r o z e n B 1 h o r i z o n made up o f m o t t l e d o l i v e g r a y s i l t loam.

A l l t h r e e s t a n d s i n p l o t s e t 2 a r e a l s o l o c a t e d on S a u l i c h s i l t loam s o i l s .

P l o t s e t 3 , c o n s i s t i n g o f an unburned c o n t r o l and a h e a v i l y burned s t a n d s i t u a t e d on a r i d g e t o p , i s i n an a r e a o f s o i l c l a s s e d a s F a i r p l a y s i l t loam. These s o i l s a r e modera t e ly w e l l d r a i n e d t o somewhat p o o r l y d r a i n e d and a r e c h a r a c t e r i s t i c o f upper s l o p e s and r i d g e t o p s . P e r m a f r o s t , if p r e s e n t , i s a t s u b s t a n t i a l d e p t h s ( a t l e a s t 1 5 0 cm). F a i r p l a y s o i l s t y p i c a l l y have a r e l a t i v e l y t h i n o r g a n i c l a y e r o v e r m o t t l e d d a r k g ray i sh -b rown g r a v e l l y s i l t loam which v a r i e s from 50 t o 100 cm i n t h i c k n e s s o v e r s c h i s t bedrock . Gravel c o n t e n t , made up o f a n g u l a r s c h i s t f r a g m e n t s , r anges from v e r y l i t t l e t o 35 p e r c e n t by volume.

U n f o r t u n a t e l y , t h e two p l o t s i n t h e a r e a o f aspen were n o t w i t h i n t h e s o i l s u r v e y a r e a . T h e r e f o r e , t h e s o i l s i n t h a t a r e a have n o t been d e s c r i b e d and c l a s s i f i e d .

S o i l taxonomic u n i t s a t t h e s u b o r d e r l e v e l f o r t h e S a u l i c h and E s t e r s e r i e s i s H i s t i c P e r g e l i c Cryaquept and f o r F a i r p l a y , Aquic C r y o r t h e n t .

Effects of burning on forest floor characteristics5

One of the outstanding characteristics of taiga soils is the thick organic layer which generally overlies the mineral soil. These layers, mainly comprised of organic matter produced by mosses and lichens, as well as vascular plant litter, are especially thick under black spruce stands, where they may reach depths of 50 cm or more. The degree to which these layers are consumed by fire controls, to a large extent, characteristics of the postfire community. Site factors greatly influenced by depth of burning in the organic layer include soil temperature and thickness of the active layer, levels of available soil nutrients and subsequent rates of mineralization, and condition of the seed bed during initial stages of secondary succession. The amount of mineral soil exposed as a result of burning is an especially important consideration because it offers the most suitable seed bed for germination of all species of Alaska taiga trees and most of the shrubs (Viereck 1973).

In the Wickersham Dome study area, observations of forest floor characteristics in both burned and unburned stands were conducted during the fall of 1971. At 20 points within each of eight stands, a 15-cm-diameter core of the forest floor was removed, including organic material as well as a portion of the mineral soil. After the cores were separated into mineral and organic components, the organic portion was taken to the laboratory, ovendried, and weighed. The depth of the organic layer was measured on the side of the hole after the core was removed. Data for each plot were summarized by total thickness, weight, and bulk density of the organic layer.

The data were analyzed for differences between location and intensity of burn. The statistics are intended for descriptive purposes for an understanding of the magnitude of the observed effects rather than conclusive inferences from the data. The only statistically significant difference in the thickness of the layer was between the heavily burned stand and the unburned control in plot set 1.

Examination of organic layerthicknesses (table 3) indicates that plot set 3, on the ridgetop, had a much thinner litter and moss layer; and less litter (1.0 cm) was removed by the fire. In plot set 2, comparisons of the burned stand with the unburned control indicate reductions of 3.35 cm in thickness of the forest floor in the heavily burned stand and 1.90 cm in the lightly burned stand. Stands in plot set 1 had the thickest organic layers, and more material was apparently consumed by the fire.

his section was prepared by N. V. Noste, Fire Scientist, and R. J . Barney, Fire Scientist, Forest Service, U.S. Department of Agriculture, Northern Forest Fire Laboratory, Missoula, Mont . ; and K. P . Burnham, Biometri- cian, Fish and Wildlife Service, U.S. Department of the Interior, Western Energy and Land Use Team, Fort Collins, Colo.

Table 3--Thickness, ovendry weight, and bulk density of forest floor layers in 8 burned 1/

stands and unburned controls in the Wickersham Dome fire study area-

Plot set 1, west-facing slope of 12-20 percent: Unburned control Lightly burned Heavily burned

Plot set, slope, and treatment

Plot set 2, very gentle, east-facing slope: Unburned control Lightly burned Heavily burned

Plot set 3, ridgetop: Unburned control Heavily burned

Grams per cubic centimeter

1'~ach value represents the mean of 20 measurements.

Bulk density Total thickness

After the fire, the difference in thickness of the forest floor between the unburned control and the heavily burned stand was 10.30 cm; the difference between the lightly burned stand and control was 5.70 cm. Differences among all three treatments in plot set 1 were found to be statistically significant (table 3).

Weight

Mean Mean

A statistically significant interaction exists between location and intensity. A pattern of consistently less reduction in forest floor thickness from the lower stands (plot set 1) toward the ridgetop can be recognized. More reduction of the organic layer progressing from the light to the heavy intensity burn may also contribute to the significant interaction.

Mean Standard deviation

Standard deviation

Apparently because of the extreme variability in weight values, neither the light nor the heavy burns removed sufficient organic material to consistently show a significant weight loss; and there was no apparent difference in weight relative to burn intensity. The extreme variability in forest floor weights may have been at least partially caused by the difficulty encountered in obtaining a clean separation between organic and mineral soil. Because of this, the organic layer samples were contaminated by variable amounts of mineral soil particles.

Standard deviation

In summary, it appears that the Wickersham Dome fire removed only relatively small portions of the forest floor materi,al. Although comparisons of depths of organic layers in burned areas with those in the unburned controls consistently indicated reductions with burning, in two out of five instances these differences were not statistically significant. The greatest reduction in forest floor thickness occurred on plots having the thickest layers, and even here the heavily burned layer was almost two-thirds as thick as that in the unburned control.

Mineral soil characteristics following burning6

Most studies of fire and soil relationships have shown that burning may have significant effects on mineral soil properties-- especially in intense fires, the fertility of the surface soil is often altered considerably. In temperate regions of the United States, changes resulting from burning generally indicate reduced quantities of organic matter, nitrogen, and in some instances, phosphorus, but significantly increased amounts of exchangeable cations, such as potassium, calcium, and magnesium, as well as an increase in soil pH (Dyrness 1963). Lutz (1956) in Alaska and Scotter (1971) in northern Canada, however, reported an increase not only in exchangeable calcium and potassium but also in nitrogen and phosphorus after fire. The increased amounts of nitrogen and phosphorus in the taiga probably represent a fire-generated release of these elements to the mineral soil from deep, overlying organic layers. In more temperate regions, forest floor layers are usually not as thick.

To determine possible effects of the Wickersham Dome fire on soil properties, we analyzed samples of mineral soil in the laboratory. These samples were collected in the fall of 1971 concur- rently with the organic layer samples and consisted of cores 15 cm in diameter, which included the upper 15 cm of the mineral soil. In each of the 11 plots (9 in black spruce and 2 in aspen) 20 samples were collected; 4 from each plot were randomly selected for soil analysis. Laboratory determinations included particle size distribution; pH; cation exchange capacity; exchangeable potassium, calcium, and magnesium; available phosphorus; and total nitrogen.

Results of soil analyses are shown in table 4. For purposes of comparison, data are grouped by plot sets, and each set contains at least one unburned control plot as well as a nearby burned plot (table 2).

Close inspection of the results reveals a high degree of var- iation among the plots, especially in chemical properties (table 4). Because of this, it is impossible to discern any consistent differences in soil properties between the burned stands and unburned controls. There are several possible reasons for this lack of correlation. The first, and perhaps the most important, is the depth of mineral soil sampled (15 cm). Since the most pronounced effects of burning would be expected in the surface 2-3 cm of soil, the sampling procedure may have effectively masked differences at the surface of the mineral soil. In addition, inherent soil variability may be sufficient in this area to preclude the possibility

6 ~ h i s section was prepared by N. V. Noste, Fire Scientist, and R . J . Barney, Fire Scientist, Forest Service, U.S. Department of Agriculture, Northern Forest Fire Laboratory, Missoula, Mont.; and C. T. Dyrness, Supervisory Soil Scientist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

Table 4--Results of analyses of samples o f t h e 0- t o 15-cm l a y e r o f mineral s o i l f o r 11 s tands a f t e r t h e 1971 Wickersham Dome f i r & /

S e t 1: Unburned con t ro l Light ly burned Unburned control?' Heavily burned

S e t 2: Unburned con t ro l L igh t ly burned Heavily burned

Se t 3: Unburned con t ro l Heavily burned

P l o t s e t and

t reatment

Se t 4: Unburned control Heavily burned

Si.Lo. Si.Lo. Si.Lo. Si.Lo.

S i . Si.Lo. Si.Lo.

Si.Lo. Si.Lo.

Si.Lo. Si.Lo.

Sand

BLACK SPRUCE

ASPEN

S i l t

Percent

0.45041 .38365 .26790 .I6747

.28676

.I8583

.31804

,06779 .I6791

.31914

.20924 - ---

L l ~ a c h value represen t s the mean of 4 determinations.

/ S i . ~ o . = silt loam: S i . = silt.

?/plot added i n 1972.

Clay Textural

class?/ pH Cat ion

exchange capac i ty

Exchangeable Available P K

Total N Ca Mg

of s u c c e s s f u l l y c h a r a c t e r i z i n g t h e e f f e c t s o f b u r n i n g on t h e b a s i s of such a c o m p a r a t i v e l y s m a l l sample . I f t h i s i s t h e c a s e , measurements of samples c o l l e c t e d from t h e same l o c a t i o n b e f o r e and a f t e r bu rn ing would be much more l i k e l y t o r e f l e c t t h e a c t u a l e f f e c t s of f i r e .

Although t h e e f f e c t s of bu rn ing on t h e s o i l samples a r e n o t a p p a r e n t , t h e d a t a do r e f l e c t c e r t a i n d i f f e r e n c e s ( t a b l e 4 ) . P e r - haps t h e most s t r i k i n g i s t h e a p p r e c i a b l y h i g h e r amounts o f a v a i l - a b l e phosphorus i n s o i l s under a s p e n . Th i s i s n o t s u r p r i s i n g ; i t i s w e l l known t h a t aspen l i t t e r c o n t a i n s much l a r g e r q u a n t i t i e s o f phosphorus t h a n does s p r u c e l i t t e r (Rodin and B a z i l e v i c h 1967) . Other d i f f e r e n c e s , a p p a r e n t l y a l s o a f u n c t i o n o f p l o t l o c a t i o n , a r e n o t i c e a b l e . For example, s o i l from t h e unburned c o n t r o l on t h e r i d g e t o p ( p l o t s e t 3) has a c o n s i d e r a b l y lower t o t a l n i t r o g e n c o n t e n t and i s a l s o lowes t i n c a t i o n exchange c a p a c i t y and exchange- a b l e ca l c ium and magnesium.

On t h e b a s i s of t h e s e r e s u l t s , we recommend t h a t m i n e r a l s o i l samples be c o l l e c t e d i n d e p t h inc remen t s of 2 - 3 cm a t many l o c a - t i o n s i n f u t u r e s t u d i e s o f f i r e e f f e c t s . I n a d d i t i o n , sampl ing s h o u l d be done a t i n t e r v a l s a f t e r t h e f i r e s o t h e r e d i s t r i b u t i o n of m o b i l i z e d e l emen t s by l e a c h i n g o r o t h e r p r o c e s s e s can be fo l lowed .

Effect of burning on soil temperature

One o f t h e i m p o r t a n t changes t a k i n g p l a c e i n t h e s o i l a f t e r f i r e i s m o d i f i c a t i o n o f t e m p e r a t u r e s . Because o f t h e i n c r e a s e i n s u r f a c e a b s o r p t i o n o f s o l a r h e a t , t h e reduced t h i c k n e s s of t h e o r g a n i c l a y e r , and t h e l a c k of s u r f a c e v e g e t a t i o n , t e m p e r a t u r e s t e n d t o be warmer i n a burned s o i l t h a n i n an unburned s o i l .

To compare s o i l t e m p e r a t u r e s i n t h e burned and unburned s t a n d s i n p l o t s e t 3 ( t a b l e 2 ) , we i n s t a l l e d a s e r i e s o f t h e r m i s t o r s a t t h e f o l l o w i n g d e p t h s : f o r e s t f l o o r s u r f a c e , 5 cm i n t h e o r g a n i c l a y e r , o r g a n i c - m i n e r a l s o i l i n t e r f a c e , 10 cm below m i n e r a l s o i l s u r f a c e , 20 cm below m i n e r a l s o i l s u r f a c e , and 50 cm below m i n e r a l s o i l s u r f a c e .

These t e m p e r a t u r e s were r e c o r d e d once a week abou t noon th rough- o u t t h e y e a r .

Graphs f o r s o i l t e m p e r a t u r e s a t 5 cm i n t h e o r g a n i c l a y e r and a t t h e 1 0 - and 50-cm d e p t h s i n t h e m i n e r a l s o i l a r e shown i n f i g u r e s 6 , 7 , and 8 .

h his sec t ion was prepared by L . A . Viereck, P r inc ipa l P lant Ecologis t , and M. J . Foote, General B io log i s t , USDA Fores t Serv ice , P a c i f i c Northwest Forest and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

Figure 8 . - -Soi l t e m p e r a t u r e a t a d e p t h o f 50 cm i n the m i n e r a l s o i l a t burned and unburned c o n t r o l s i tes d u r i n g the 1 s t year a f t e r b u r n i n g .

1971 1972 1972

For the 10-cm depth (fig. 7), temperatures during the fall of 1971, the same year as the fire, were similar in burned and unburned areas until the end of January. During February and until mid-March, temperatures continued to decline in the unburned stand until a low of -3Oc was reached in mid-March. In the burned stand, temperatures remained close to OOC until April 10. During May and early June, the temperatures at 10 cm in the mineral soil were similar. After the final melting of the overlying snow in mid-May to late May, there was a rapid rise in soil temperatures in the burned stand; a high of 1 0 . ~ ~ ~ was reached on approximately July 20. The soil in the unburned control warmed much more slowly during the summer with a much greater timelag and did not reach its warmest point, ~ O C , until September 13, long after the close of the a~tive growing season and within a week of the first snowfall. During the cooling period in September and October, the rates were similar; but the burned stand remained warmer until the end of October, at which time the temperatures were once again about the same.

oc NOV. DEC.

A comparison of the 10-cm soil temperature (fig. 7) with air temperature illustrates an interesting and well-documented timelag. Although the coldest air temperatures occurred the first 2 weeks in January, the soil temperatures at 10 cm did not reach the coldest point until 2 months later. Similarly, summer air temperatures were at a maximum in mid-June, but soil temperatures at 10 cm did not reach a maximum until July 20 in the burned area and the middle of September in the unburned control.

If the soil temperatures are compared with air temperatures, as snow melts we can see that, although air temperatures are well above the freezing point by mid-May, soil temperatures do not begin to rise above OOC until all the snow is melted.

I I I I I I I I I I I I I I JANUARY FEE. MARCH APRIL MAY JUNE JULY AUGUST SEPT. OCTOBER NOV. DEC. 'C

In the fall of 1972 the permanent snow cover came while soil temperatures were relatively warm. This may have resulted in the rapid cooling in the organic layer in mid-September. On the other hand, the snow cover seems to have insulated the soil from the effects of the cold period in late October.

Figures 6 and 8 show soil temperatures for the 5-cm depth in the organic layer and for the 50-cm depth in mineral soil. As would be expected, the litter layer shows a much wider fluctuation of temperatures. Some of the same patterns as occurred at the 10-cm depth in the mineral soil, however, are apparent. A surprising fact is that, during most of-the summer. soil temperature for the organic layer in the burned stand were 2'-4' higher than in the unburned control (fig. 6), but at the time of the highest temperature in July the temperature in the organic layer beneath living mosses in the unburned control was greater than that in the burned forest floor with a charred surface.

As expected, mineral soil temperatures at a depth of 50 cm showed less fluctuation and range than those at 10 cm or in the organic layer (fig. 8). Also, the timelag was longer, the minimum temperature occurred in April, and no warming occurred until after mid-June in the burned stand and mid-July in the unburned control.

Temperature-sensitive pellets were placed on the surface of the blackened, burned organic material on June 15, just after the hot- test days of the summer. During the week of June 15-22, the temperature reached at least 5g0c. During July, the highest surface temperatures were between 55Oc and 50'~; and by August they were between 48'~ and 55'~. Surface temperatures as high as those in June are considered lethal to tree seedlings.

An important effect of wildfire in the taiga of Alaska is alter- ation of the thickness of the active layer (thawed soil above the permafrost layer). Few data are available for thickness of the active layer after fire in forest stands in Alaska, but the active layer generally is known to be thicker in successional stands after fire than it is in unburned black spruce forests. The actual heat produced by the fire is probably unimportant, as the organic layer seldom burns to the permafrost boundary. Brown (1965) stated, "A fire may burn trees, brush, and even the surface of the moss without altering the underlying permafrost." After a fire, however, the changes in the surface albedo and the removal of the vegetation and some of the organic mat result in warmer soils and deeper thawing. After a fire in the black spruce type at Inuvik, in Northwest Territories, Canada, Hegginbottom (1971) reported that by the summer after the fire, the thaw was 9 cm deeper in burned than in unburned

his sec t ion was prepared by L . A . Viereck, P r inc ipa l P l an t Ecologis t , and M. J . Foote, General Bio logis t , USDA Fores t Serv ice , P a c i f i c Northwest Forest and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

s t a n d s . From e i g h t permanent p o i n t s on t h e Inuv ik f i r e , Mackay (1970) r epor t ed an average i n c r e a s e of thaw of 24.1 cm (149 p e r c e n t ) by t h e end of t h e f i r s t summer a f t e r t h e f i r e and 24.8 cm (171 p e r c e n t ) by t h e end o f t h e second summer. Cody (1964) r e p o r t e d t h a t 3 y e a r s a f t e r a t a i g a f i r e i n t h e Reindeer Graz ing Reserve on t h e Mackenzie D e l t a , t h e p e r m a f r o s t had r eceded t o a dep th o f 40 cm o r more, and t h e r e c e s s i o n o f t h e i c e had caused s u r f a c e subs idence which r e s u l t e d i n a hummocky t e r r a i n .

A t t h e end o f t h e f i r s t summer a f t e r an August and September burn i n e a s t e r n Alaska , L o t s p e i c h e t a l . (1970) found no s i g n i f i c a n t d i f f e r e n c e i n thaw d e p t h - - b o t h burned and unburned s t a n d s had thawed t o approx ima te ly 70 cm. I n an Eriophorum t u s s o c k t u n d r a w i t h i n t h e t a i g a o f A l a s k a , Wein (1971) r e p o r t e d a 130- t o 1 5 0 - p e r c e n t i n c r e a s e i n t h e a c t i v e l a y e r i n e a r l y summer a f t e r a f i r e t h e p r e v i o u s y e a r , b u t on ly 115- t o 1 2 0 - p e r c e n t d i f f e r e n c e by t h e t ime o f maximum thaw i n t h e f a l l . Brown e t a l . (1969) r e p o r t e d an i n c r e a s e d thaw of 160 and 140 p e r c e n t 4 y e a r s a f t e r a f i r e i n a b l a c k s p r u c e / ~ r i o p h o r u m t u s s o c k t y p e i n e a s t e r n Alaska . They a l s o r e p o r t e d a 141- and 1 5 2 - p e r c e n t i n c r e a s e i n thaw d e p t h i n a 1 - y e a r - o l d bu rn i n an Eriophorum t u s s o c k t y p e w i t h s c a t t e r e d b l a c k s p r u c e i n c e n t r a l Alaska .

A t t h e n o r t h e r n l i m i t of f o r e s t v e g e t a t i o n i n R u s s i a , however, f i r e may r e s u l t i n a t h i c k e n i n g of t h e a c t i v e l a y e r , fo l lowed i n a few y e a r s by a r i s e i n t h e p e r m a f r o s t upper s u r f a c e . Kryuchkov (1968) r e p o r t e d t h a t f i r e f i r s t caused a thawing o f t h e upper p e r m a f r o s t l a y e r s w i t h a r e s u l t a n t r e l e a s e o f m o i s t u r e , c r e a t i n g c o n d i t i o n s which s t i m u l a t e d t h e growth o f t h e Eriophorum c o v e r . A s a r e s u l t o f t h e i n s u l a t i n g e f f e c t s o f t h e t h i c k e r v e g e t a t i o n mat , t h e a c t i v e l a y e r was o n l y 40-45 cm t h i c k a few y e a r s a f t e r t h e f i r e , whereas b e f o r e t h e f i r e i t had been 50-70 cm.

A t Wickersham Dome we s t u d i e d t h e annual f r e e z i n g and thawing c y c l e s and t h e d e p t h t o p e r m a f r o s t by t h r e e methods: .

1. Weekly r e a d i n g s o f s o i l t e m p e r a t u r e a t two s i t e s , one i n a h e a v i l y burned s t a n d and one i n an unburned c o n t r o l a t t h e r i d g e - t o p s i t e ( p l o t s e t 3 ) .

2 . F r o s t t u b e s f i l l e d w i t h sand and a f l u o r e s c e i n dye (Rickard and Brown 1972) were i n s t a l l e d i n s i x s t a n d s , t h r e e burned s t a n d s and t h r e e unburned c o n t r o l s .

3. Probe l i n e s were e s t a b l i s h e d s o we cou ld f o l l o w t h e r e c e s - s i o n o f t h e f r o s t l i n e i n burned s t a n d s , unburned c o n t r o l s , and t h e f i r e l i n e s ; 10 p robes were t a k e n a t each s i t e and ave rage dep th t o f r o z e n s o i l was r e c o r d e d .

We used t h e f r o s t t u b e s t o f o l l o w t h e f r e e z i n g i n t h e f a l l and w i n t e r , b u t t h e probe l i n e s were b e t t e r f o r f o l l o w i n g t h e thaw d u r i n g t h e summer.

Because o f t h e v a r i a t i o n i n d e p t h t o bedrock and d e p t h t o which f r o s t t u b e s cou ld be i n s t a l l e d , g e n e r a l comparisons between a l l t h e burned s t a n d s and unburned c o n t r o l s were i m p o s s i b l e . I n s t e a d , o b s e r v a t i o n s o f p e r m a f r o s t were c o n c e n t r a t e d on t h r e e s t a n d s on o r g a n i c s o i l s n e a r Cushman Creek: a h e a v i l y burned b l a c k s p r u c e s t a n d (BS-lH), i t s unburned c o n t r o l (BS-4C)- -p lo t s e t 1 A i n t a b l e 2 , and an a d j a c e n t h e a v i l y b u l l d o z e d f i r e l i n e .

I n t h e f a l l o f t h e f i r s t summer a f t e r t h e f i r e , t h e r e was no s i g n i f i c a n t d i f f e r e n c e between burned s t a n d s and unburned c o n t r o l s . Probing i n f o u r s t a n d s i n t h e burn showed thaw t o a n ave rage d e p t h of 44 cm, whereas i n t h e a d j a c e n t unburned c o n t r o l s t h e ave rage thaw was t o 47 cm.

F i g u r e 9 shows t h e f r e e z e - t h a w c y c l e i n a h e a v i l y burned s t a n d and an unburned c o n t r o l f o r t h e 1st y e a r a f t e r t h e f i r e . I n t h e f a l l a f t e r t h e f i r e , t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e d e p t h of t h e thaw (40 cm i n t h e unburned c o n t r o l and 41 cm i n t h e h e a v i l y burned s t a n d ) . During t h e f i r s t w i n t e r a f t e r t h e b u r n , f r e e z i n g o c c u r r e d more r a p i d l y i n t h e unburned c o n t r o l t h a n i n t h e burned s t a n d . The a c t i v e l a y e r was comple te ly f r o z e n by December 1 2 i n t h e unburned c o n t r o l b u t n o t u n t i l J a n u a r y 15 i n t h e burned s t a n d .

The n e x t summer, thawing was deepe r i n t h e burned s t a n d t h a n i n t h e unburned c o n t r o l . Although t h e snow mel t ed 2 weeks e a r l i e r i n t h e burned s t a n d t h a n i n t h e unburned, thawing was s i m i l a r i n b o t h u n t i l June 7 ; a f t e r t h a t , thawing was more r a p i d i n t h e burned s t a n d . Thawing t o n e a r l y t h e maximum d e p t h o f 6 3 cm had o c c u r r e d by August 23 i n t h e burned s t a n d and t o a maximum of 40 cm by September 6 i n t h e unburned c o n t r o l . Thus, dep th of thawing i n t h e burned s t a n d t h e f i r s t summer a f t e r t h e f i r e was 157 p e r c e n t of t h a t i n t h e unburned c o n t r o l . Probing was a l s o c a r r i e d o u t i n t h e f i r e l i n e between t h e two s t a n d s . The r a t e of thaw d u r i n g 1972 was more r a p i d i n t h e f i r e l i n e t h a n i n e i t h e r t h e c o n t r o l o r t h e h e a v i l y burned s t a n d . Maximum d e p t h o f thaw i n t h e f i r e l i n e was 88 cm o r approx ima te ly 2 0 0 p e r c e n t o f t h a t i n t h e unburned c o n t r o l .

197 1972

1 1 1 ~ 1 1 1 1 , ~ 1 1 1 1 1 , 1 1 1 1 1 1 1 1 , , ,

OCT NOV DEC JAN. FEB MAR APR MAY JUN JUL AUG SEPTocm - 10

FROZEN -'-*. '-.

\ ......,.."...... .

UNBURNED - BURNED .---a-

Figure 9.--Freeze-thaw c y c l e i n a h e a v i l y burned s t a n d and a n unburned c o n t r o l f o r the 1st year a f t e r the f i r e . (Reproduced from: ~ i e r e c k , L e s l i e A. 1973. E c o l o g i c a l e f f ec t s o f river f l o o d i n g and forest fires o n permafros t i n the t a i g a o f A l a s k a . In North American c o n t r i - b u t i o n , p e r m a f r o s t , second i n t e r n a t i o n a l c o n f e r e n c e , p. 66 . Na t l . Acad. S c i . , Wash ing ton , D . C . ) .

F i g u r e 1 0 compares t h e thawing d e p t h s i n t h e h e a v i l y burned s t a n d s and t h e unburned c o n t r o l s and on t h e f i r e l i n e f o r t h e f i r s t 3 y e a r s a f t e r t h e f i r e . I n t h e unburned c o n t r o l t h e thaw p a t t e r n s a r e s i m i l a r each y e a r ; maximum thaw d e p t h i s approx ima te ly 4 5 cm. Table 5 g i v e s t h e d e p t h o f thaw i n t h e t h r e e a r e a s th rough t h e summer o f 1976.

I n t h e burned s t a n d t h e r e h a s been an i n c r e a s e each y e a r i n t h e maximum d e p t h o f thaw and i n t h e r a t e o f thaw ( t a b l e 5 ) .

The f i r e l i n e has shown t h e most d r a m a t i c change i n t h e d e p t h of thaw ( t a b l e 5 ) . I n a d d i t i o n , t h e r e h a s been some s u b s i d e n c e from t h e l o s s o f p u r e i c e d e p o s i t s s o t h a t t h e a c t u a l d e p t h o f thaw i n r e l a t i o n s h i p t o t h e o r i g i n a l s u r f a c e may be somewhat g r e a t e r .

I n t h e 5 y e a r s a f t e r t h e f i r e , t h e r e seemed t o be no s lowing down o f t h e annua l i n c r e a s e i n thaw d e p t h i n e i t h e r t h e burned s t a n d o r t h e f i r e l i n e . With complete r e c o v e r y o f t h e s u r f a c e v e g e t a t i o n , t h e d e p t h o f thaw i s expec ted t o s t a b i l i z e and e v e n t u - a l l y r e t u r n t o t h a t o f t h e o r i g i n a l s t a n d .

-----a 1974 ) - 1972 e- 4 7973 BURNED STAND @-----a 1974 - 1972

0-----4 1974

I *- -0 1973 FIRELINE

200 I I

MAY JUNE JULY AUGUST SEPT. OCT.

Figure 10. --Depth o f thaw i n a heavily burned stand, on a cleared f i r e l ine , and i n an unburned control for 3 years a f t e r the f i r e .

cm I 1 1 I

Table 5--Maximum depths of thaw i n an unburned cont ro l , a burned black spruce s tand, and a f i r e l i n e f o r t he 6 summers a f t e r a June 1971 wi ld f i r e a t Wickersham Dome

Unburned control: 1971 1972 1973 1974 1975 1976

Stand and year

Burned i n June 1971: 1971 1972 1973 1974 1975 1976

F i r e l i ne , June 1971: 1971 1972 1973 1974 1975 1976

Centimeters

Annual increase i n depth of thaw

Maximum depth of thaw

Percent Centimeters

Percent of thaw i n unburned cont ro l

Climatic Factors

Snow depths in burned and unburned forests.

Snow d e p t h s were r e c o r d e d weekly i n t h r e e burned b l a c k s p r u c e s t a n d s (BS-SH, BS-lL, and BS-1H) and t h r e e unburned c o n t r o l s (BS-3C, BS-lC, and BS-4C) from two snow s t a k e s i n each s t a n d . F i g u r e 11 shows t h e snow d e p t h s f o r t h e two s t a n d s i n p l o t s e t 3 (BS-3C and BS-3H) ( t a b l e 2 ) . These s t a n d s show a p a t t e r n t h a t c h a r a c t e r i z e d a l l s i x o f t h e sampled s t a n d s . I n 1971 t h e f i r s t snow f e l l i n l a t e September and by October 1 4 , when a l l s t a k e s were r e a d t h e f i r s t t i m e , t h e r e was 1 2 cm o f snow on t h e ground.

Y This sec t ion was prepared by L . A. Viereck, Pr inc ipa l P lant Ecologist , and A . E . Helmers, Research Hydrologist ( r e t i r e d ) , USDA Forest Service, Pac i f i c Northwest Forest and Range Experiment S ta t ion , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

F i g u r e 11.--Depths o f snow o n burned b l a c k s p r u c e s t a n d s and unburned c o n t r o l s from November 1971 t o December 1972, Wickersham Dome.

1971 1972 1972 c- NOV. DEC. JANUARY FEE MARCH APRIL MAY JUNE JULY AUGUST SEPT OCTOBER NOV. DEC. c,

Major s n o w f a l l s and p e r i o d s of s e t t l e m e n t and compaction can be s e e n i n t h e s t e p l i k e cu rve from November 1 t o March 29, t h e t ime o f maximum snow accumula t ion ( approx ima te ly 100 cm i n each s t a n d ) . During t h i s p e r i o d , t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n snow d e p t h s between t h e burned s t a n d s and unburned c o n t r o l s .

110

There was no a p r e c i a b l e snowmelt u n t i l t h e d a i l y mean tempera- { t u r e r o s e above 0 C a t t h e end o f A p r i l . Melt was t h e n ex t r eme ly r a p i d s o t h a t by May 24 a l l snow was gone from b o t h t h e unburned c o n t r o l and t h e burned s t a n d . Snowmelt was much more r a p i d i n t h e burned s t a n d t h a n i n t h e c o n t r o l . On May 3 b o t h s t a n d s had 80 cm o f snow; by t h e f o l l o w i n g week, t h e snow i n t h e burned s t a n d had been reduced t o 1 3 cm, whereas t h a t i n t h e unburned c o n t r o l was 42 cm. On May 17 t h e r e were o n l y o c c a s i o n a l p a t c h e s o f snow i n t h e burned s t a n d , whereas t h e unburned c o n t r o l s t i l l had a n e a r l y con t inuous cove r 1 3 cm i n d e p t h . The burned s t a n d was f r e e o f snow abou t 7 days b e f o r e t h e unburned c o n t r o l was. The e f f e c t t h a t t h i s had on p l a n t growth was d r a m a t i c a l l y shown i n t h e lower , h e a v i l y burned s t a n d , where clumps o f sedge t u s s o c k s ( ~ r i o p h o r u m vaginatum L . ) were i n f u l l f l ower on May 1 7 w h i l e t h e r e was s t i l l a n e a r l y con t inuous snow cove r i n t h e a d j a c e n t unburned c o n t r o l .

Snow came e a r l y i n t h e f a l l o f 1972. The f i r s t snow f e l l on September 20 and remained on t h e ground f o r t h e r e s t o f t h e s e a s o n . Th i s gave a snowfree p e r i o d o f 126 days f o r t h e burned s t a n d s and 119 days f o r t h e unburned c o n t r o l s .

I I I I I I I I I I I I i

- - 110

100 - - 90 - -

- -

100

9 0

8 0

7 0

3 0 - 20 - 10 - - 10

0 . 0

Air ~ e r n ~ e r a t u r d ' O

Air temperatures were recorded with a thermograph in a standard weather bureau shelter in both the heavily burned stand and the unburned control in plot set 3 (table 2). Figure 12 illustrates the average daily air temperature within these stands. There were no significant differences in the shelter temperature between the two stands. The temperatures during this period showed a typical pattern for interior Alaska: occasional intensive cold periods in December, January, and February; and a general warming trend through March, April, and May, with the average daily temperature rising above OOC at the end of April. The warmest period of the summer was in mid-June, followed by generally lower temperatures in July and August. The daily mean temperature crossed below the freezing point for the first time in mid-September but was above it in an exceptionally warm period in mid-October.

F i g u r e 1 2 . --Average d a i l y a i r t e m p e r a t u r e i n a burned b l a c k s p r u c e s t a n d and a n a d j a c e n t unburned c o n t r o l .

'O~his section was prepared by L. A. Viereck, Principal Plant Ecologist, and A. E. Helmers, Research Hydrologist (retired), USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

Table 6 provides a monthly summary of the air temperatures from November 1971 to December 1972. In 1972, the average daily temperature was - 3 . 5 ~ ~ ~ for the burned stand and -3.44'~ for the unburned control. This compares with -4.s0c at the Fairbanks International Airport for the same period and -3.5'~ for the 30-year average. From these 1971-72 records it appears that the Wickersham Dome area is slightly cooler than Fairbanks in the summer and slightly warmer during the extreme cold periods in winter. This pattern has held in subsequent years. The summaries for 1973 and 1974 are not included in this report but are on file at the Institute of Northern Forestry, Fairbanks.

Table 6--Average a i r temperatures ( O C ) i n a heavi ly burned stand and an adjacent unburned con t ro l ( p l o t s e t 3 1 , November 1971 t o December 1972

1971 :

November December

1972 :

January February March Apri l May June Ju ly August September October November December

Year and month

Average d a i l y temperature f o r 1972: Burned stand -3.55 Unburned cont ro l -3.44

Stream Water Quality'

Since most of the burned area drains into Washington Creek, a limited sampling program was initiated on this stream in an attempt to determine the effects of the fire on water quality. F. B . Lotspeich, of the Environmental Protection Agency's Arctic Environ- mental Research Laboratory, established four water sampling stations

Burned stand

his section was prepared by F. B. Lotspeich, Soil Scientist, Special Studies Branch, U.S. Environmental Protection Agency, Corvallis, Oregon; and C. T. Dyrness, Supervisory Soil Scientist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

Unburned cont ro l

Average Minimum Maximum Average Minimum Maximum

on Washington Creek (two below the burned area and two above it) and obtained samples the day the fire was controlled and 1 and 2 weeks after it was controlled. These samples of stream water were analyzed in the laboratory to determine whether the chemical retardan,ts dropped had enriched the water and how much sedimenta- tion resulted from erosion of the firelines. Results were summarized by Lotspeich (1972) .

Although measurements of suspended sediment were not obtained for the first set of water samples, the sediment content of Wash- ington Creek below the burned area was estimated to be about 300-500 mg/liter at the time the fire was controlled. The primary source of sediment was thought to be erosion of firelines caused by thawing of the permafrost. Therefore, immediately after the fire, the Bureau of Land Management constructed water bars across firelines in an effort to curtail this form of erosion. These measures were apparently successful; water samples collected several days later were uniformly low in suspended sediment content--the maximum value, 19 mg/liter. Just prior to the third and last sampling (about 2 weeks after control of the fire), sufficient rain fell to cause Washington Creek to rise. Apparently some sediment was still entering the drainage from the bulldozed firelines because at this time maximum sediment content was 97 mg/liter.

Little effect of the chemical retardant could be detected in the water samples. Nitrogen content of samples collected above and below the burned area were about the same. Although amounts of total phosphate in samples collected below the fire-were somewhat higher than those in control samples, amounts never exceeded the content recommended for aquatic life in "Water Quality Criteria" (Report of the National Technical Advisory Committee, Federal Water Pollution Control Administration, 1968, p. 27-110).

BIOTIC FACTORS Vegetation Analysis'

One of the main objectives of the Wickersham Dome study was to follow the development of vegetation after the fire. To accomplish this, we followed vegetation trends in all 11 sample stands selected for study in 1971 and 1972 (table 2)--nine stands are in the black spruce type and 2 in aspen.

In each sample stand, 20 permanent plots were located at inter- vals of 30 m, usually in four rows of 5 plots. Vegetation analysis

1 2 ~ h i s sec t ion was prepared by L . A. Viereck, Pr incipal Plant Ecologist , and M. J . Foote, General Biologis t , USDA Forest Service, Pac i f i c Northwest Forest and Range Experiment S ta t ion , I n s t i t u t e of Northern Forestry, Fairbanks, Alaska.

a s s l i g h t l y mod i f i ed from a method d e s c r i b e d by Ohman and Ream 1971) . A t each l o c a t i o n , t h e cove r o ground v e g e t a t i o n , h e r b s , nd low s h r u b s was de termined i n a 1-m5 p l o t . T a l l s h r u b s were

coun ted and d i a m e t e r s measured i n a 4-mZ p l o t . Tree s e e d l i n g s - - t r e e s l e s s t h a n 1.3-m i n h e i g h t - - w e r e a l s o r e c o r d e d on t h e 4-mZ p l o t .

D e n s i t y and b a s a l a r e a o f t r e e s and s a p l i n g s were de termined by t h e p o i n t - q u a r t e r method. S a p l i n g s were d e f i n e d a s t r e e s r e a c h i n g a h e i g h t o f 1 . 3 m ( b . h . ) b u t having a d i a m e t e r o f l e s s t h a n 2.54 cm.

Computer programs were used t o summarize t h e i n f o r m a t i o n . Values of p e r c e n t f r e q u e n c y , c o v e r , r e l a t i v e f r e q u e n c y , r e l a t i v e c o v e r , and impor tance were de termined f o r t h e ground c o v e r , h e r b s , and low s h r u b s . Frequency, number o f s tems p e r h e c t a r e , b a s a l a r e a , r e l a t i v e f r e q u e n c y , r e l a t i v e d e n s i t y , and r e l a t i v e dominance were de te rmined f o r t r e e s and t a l l s h r u b s , These v a l u e s were de te rmined f o r a l l s p e c i e s i n each s t a n d .

In a d d i t i o n , d a t a f o r t h e f o u r h e a v i l y burned s t a n d s and t h e two l i g h t l y burned s t a n d s were summarized and compared w i t h t h e summary o f a l l f o u r unburned s t a n d s f o r each y e a r . F i n a l l y , d a t a from a l l s t a n d s f o r each y e a r were run through a c l u s t e r i n g p r o - gram by t h e agg lomera t ive method ( O r l o c i 1967) .

The v e g e t a t i o n changes i n s e l e c t e d s t a n d s t h e f i r s t 3 y e a r s a f t e r t h e f i r e a r e shown i n t a b l e s 7 , 8 , and 9 . I n each c a s e t h e v e g e t a t i o n d a t a f o r t h e burned s t a n d a r e compared w i t h t h e p a i r e d unburned c o n t r o l .

~ . - - B s - ~ H and BS-3C a r e h e a v i l y burned and unburned b l a c k s p r u c e s t a n d s i n p l o t s e t 3 ( t a b l e 2 ) .

The o u t s t a n d i n g f e a t u r e of s t a n d BS-3H i s t h e r a p i d development o f t h e herbaceous c o v e r - - f r o m 1 p e r c e n t d u r i n g t h e summer of t h e f i r e (1971) t o 2 1 p e r c e n t by 1974 ( t a b l e 7 and f i g . 1 3 ) . I n con- t r a s t , t h e unburned c o n t r o l had o n l y 3 . 5 - p e r c e n t herbaceous c o v e r . The moss and l i v e r w o r t cove r r e t u r n e d , main ly because o f t h r e e s p e c i e s - - P o l y t r i c h u r n juniperinurn Hedw., Marchant ia polyrnorpha L . , and Ceratodon purpureus (Hedw.) B r i d . , b u t t h e r e t u r n was s low. The moss and l i c h e n s p e c i e s which made up 80 p e r c e n t o f t h e cove r i n t h e unburned c o n t r o l had n o t r e t u r n e d a t t h e end o f 3 y e a r s .

Recovery o f SaZix s c o u z e r i a n a has been r a p i d ; d e n s i t y r eached a peak o f 15,250 stems p e r h e c t a r e i n 1973 and d e c l i n e d somewhat i n 1974, b u t t h e b a s a l a r e a c o n t i n u e s t o i n c r e a s e . By 1973 t h e b a s a l a r e a o f t h e wi l low was e q u a l t o t h a t i n t h e unburned c o n t r o l and by 1974 i t was n e a r l y t h r e e t imes a s l a r g e . Rosa a c i c u l a r i s was a l s o more abundant i n t h e burn t h a n i n t h e c o n t r o l .

Few s p e c i e s invaded t h e s t a n d d u r i n g t h e 3 y e a r s a f t e r t h e f i r e . Most development was from p l a n t p a r t s t h a t remained a l i v e a f t e r t h e f i r e . Even f i r e w e e d (Epilobiurn angus t i fo l iu rn L.) was p r e s e n t i n t h e c o n t r o l ; i n t h e burned s t a n d i t developed f i r s t from s u b s u r f a c e rh izomes . L a t e r s p r e a d h a s been by b o t h rhizome and s e e d . Two e x c e p t i o n s t o t h i s a r e t h e l i v e r w o r t and moss, Marchant ia pozyrnorpha and Ceratodon p u r p u r e u s ; n e i t h e r was r eco rded i n t h e unburned c o n t r o l , b u t b o t h have s p r e a d r a p i d l y i n t h e burned a r e a , p r i m a r i l y on a r e a s o f exposed m i n e r a l s o i l .

Table 7--Analysis of vegetation i n a heavily burned ridgetop black spruce stand (BS-3H) and an adjacent unburned

control stand (BS-3C) i n black spruce fo r 4 years a f t e r a 1971 wildfir&

- - -Number of stems per hectare- - - - -Square meters per hectare- -

--

Species

Trees : Picea mariana-- Live t r e e s Dead t r e e s Saplings

Seedlings and layerings

Populus tremuloides-- Seedlings

Tall shrubs: Salix scouleriana Rosa acicularis Alnus crispa Salix sp. Rubus idaeus

Density

Total t a l l shrubs

Basal area (m2/ha) o r frequency ( percent )

1971

Low shrubs: Ledum qroenlandicum Vaccinium uliqinosum Spiraea beauverdiana Vaccinium vitis-idaea Ledum decumbens Chamaedaphne calyculata

Control 1971 1972

- -Square meters per hectare- -

Empetrum niqrum 0 0 0 0 .20 0 0 0 0 10 ~xycoccus microcarpus 0 0 0 0 .05 0 0 0 0 5

1973 1972

Total low shrubs

Herbs : Calamagrostis canadensis Rubus chamaemorus Equisetum sylvaticum

1974 1973

Cornus canadensis Geocaulon lividum Polyqonum alaskanum

Control 1974

Mertensia paniculata Epilobium angustifolium Lycopodium complanatum Equisetum arvense 0 0 0 .15 0 0 0 0 10 0 Lycopodium clavatum 0 0 0 0 .80 0 0 0 0 35

Total herbs 1.20 4.10 7.8 20.9 3.51

Mosses and lichens: Polytrichum juniperinum 0 .40 .65 5.10 1.70 0 40 65 45 65 Other mosses 0 .10 0 .10 0 5 0 5 0 Marchant ia pol ymorpha 0 .05 . l o . lo 0 5 5 5 0 Ceratodon purpureus 0 0 1.00 1.70 0 0 20 40 0 Dicranum sp. 0 0 .05 0 0 0 5 0 0 Pleurozium schreberi 0 0 0 0 56.25 0 0 0 0 90 Cladonia ranqiferina 0 0 0 0 6.05 0 0 0 0 95 Nephroma arcticum 0 0 0 0 6.45 0 0 0 0 35 Aulacomnium palustris 0 0 0 0 2.40 0 0 0 0 60 Peltiqera aphthosa 0 0 0 0 2.00 0 0 0 0 50 Cladonia spp. 0 0 0 0 1.20 0 0 0 0 40 Peltiqera canina 0 0 0 0 1.80 0 0 0 0 25 Fungi 0 0 0 0 .60 0 0 0 0 55 Cetraria islandica 0 0 0 0 .60 0 0 0 0 20 Hylocomium splendens 0 0 0 0 .50 0 0 0 0 20 Parmelia sp. 0 0 0 0 .25 0 0 0 0 25 Cetraria sp. 0 0 0 0 .10 0 0 0 0 10 Mnium sp. 0 0 0 0 .20 0 0 0 0 5

Total mosses 0 .55 1.80 7.00 61.05 Total l ichens 0 0 0 0 18.45 Total mosses and l ichens 0 .55 1.80 7.00 80.10

Total ground cover 1.80 9.05 14.90 37.35 104.81

2-- = negligible

2 7

Table 8--Analysis of vegetation i n a heavily burned stand (AS-1B) and an adjacent unburned control stand (AS-1C) i n aspen f o r 1972, 1973, and 1974 a f t e r a 1971 wi ldf i re

- -Number of stems per hectare- - Square meters per hectare

Species

Trees : Populus tremuloides-- Live t r e e s Dead t r e e s Saplings Root suckers

Picea glauca-- Seedlings

Picea mariana-- Live t r e e s Dead t r e e s Saplings Seedlings

Density

Betula papyrifera-- Live t r e e s Dead t r e e s Saplings Seedlings

1972

Basal area (&/ha) o r frequency ! percent )

Tal l shrubs: Rosa acicularis Alnus crispa

Total t a l l shrubs

1972

- - - -Cover (percent)- - - - - -Frequency (percent)- - Low shrubs:

Rihes triste .05 0 .65 -- 5 0 35 Vaccinium vitis-idaea 0 0 0 5.10 0 0 0 75 Vaccinium uliginosum 0 0 0 2.15 0 0 0 40 Linnaea borealis 0 0 0 2.75 0 0 0 10 Ledum groenlandicum 0 0 0 .65 0 0 0 25

Total low shrubs .05 0 .65 10.65

Herbs : Corydalis sempivirens 1.15 .05 .05 0 10 5 5 0 Epilobium angustifolium .45 4.9 12.0 .25 20 90 90 20 Calamagrostis canadensis .20 .50 6.8 1.45 20 30 50 80 Cornus canadensis .15 .65 1.5 4.95 15 30 40 100 Pyrola secunda 0 .05 0 0 0 5 0 0 Stellaria sp. 0 0 .1 0 0 0 10 0 Geocaulon lividum 0 0 0 .65 0 0 0 20 Lycopodium sp. 0 0 0 .50 0 0 0 10

Total herbs 2.35 6.2 20.55 7.8

Mosses and lichens: Marchantia polymorpha -25 6.6 6.9 40 45 0 Liverwort .15 0 0 0 O 10 l5 0 0 0 Polytrichum juniperinum .05 .05 1.40 .20 5 5 65 10 Fungi .05 .35 .65 .35 5 35 65 30 Ceratadon purpureus 0 20.9 31.3 0 0 100 80 0 Ptilium ciliare 0 .15 0 .35 0 10 0 10 Other mosses .75 2.00 0 0 45 5 0 0 Parmelia sp. 0 .10 0 1.25 5 0 0 70 Drepanocladus sp. 0 0 0 3.45 0 0 0 75 Pleurozium schreberi 0 0 0 4.20 0 0 0 25 Hylocomium splendens 0 0 0 1.15 0 0 0 45 Cetraria sp. 0 0 0 .30 0 0 0 30 Peltigera aphthosa 0 0 0 .50 0 0 0 5 Aulacomnium palustris 0 0 0 . lo 0 0 0 10 Cladonia sp. 0 0 0 . lo 0 0 0 10

Total mosses and l ichens 1.25 30.2 40.36 12.55 Total ground cover 3.65 36.40 61.50 31.00

1974 Control 1973 1973 Control 1974

E s t a b l i s h m e n t o f s p r u c e s e e d l i n g s has been low i n t h i s s t a n d ; o n l y 20 p e r c e n t o f t h e 4-m2 p l o t s c o n t a i n e d any s e e d l i n g s , and t h e t o t a l was o n l y 2,750 p e r h e c t a r e i n 1974. The dead b l a c k s p r u c e remained s t a n d i n g , s o t h e r e was s i g n i f i c a n t d e c r e a s e i n d e n s i t y .

2.--BS-2H, BS-ZL, and BS-2C a r e h e a v i l y bu rned , l i g h t l y bu rned , and unburned b l a c k s p r u c e s t a n d s i n p l o t s e t 2 ( t a b l e 2 ) . These t h r e e s t a n d s a r e r e p r e s e n t a t i v e o f a b l a c k s p r u c e s t a n d u n d e r l a i n by p e r m a f r o s t and w i t h a t h i c k o r g a n i c l a y e r . Tab le 8 summarizes t h e a n a l y s i s o f v e g e t a t i o n f o r t h e t h r e e s t a n d s .

Development o f v e g e t a t i o n i n t h e h e a v i l y burned s t a n d was s i m i l a r t o t h a t d e s c r i b e d f o r s t a n d BS-3H; i . e . , s low deve lop- ment o f t h e low s h r u b s and herbaceous l a y e r . The moss l a y e r developed s l o w l y , and t o t a l cove r r eached 11 p e r c e n t i n 1974-- p r i m a r i l y a r e s u l t o f t h e development of Cera todon purpureus . D e n s i t y o f dead t r e e s d i d n o t d e c r e a s e a p p r e c i a b l y a f t e r t h e summer o f t h e f i r e . Tree s e e d l i n g s became numerous, approx ima te ly 21,000 p e r h e c t a r e i n 1974. Resp rou t ing o f s h r u b s was s low; t h e t o t a l number o f t a l l s h r u b s i n t h e h e a v i l y burned s t a n d i n 1974 was o n l y a t h i r d t h a t o f t h e unburned c o n t r o l .

The l i g h t l y burned s t a n d developed i n a d i f f e r e n t manner t h a n t h e h e a v i l y burned s t a n d ( f i g . 1 4 ) . A number o f t r e e s and s a p l i n g s s u r v i v e d t h e f i r e , b u t t h e s e d i e d d u r i n g t h e 3 y e a r s a f t e r t h e f i r e s o t h a t o n l y 61 p e r h e c t a r e remained a l i v e a t t h e end of t h e 1974 s e a s o n . Because o f t h e p r e s e n c e o f e x t e n s i v e a r e a of unburned o r p a r t i a l l y burned mosses , s p r u c e s e e d l i n g s germinated i n l a r g e numbers; n e a r l y 40,000 p e r h e c t a r e were r e c o r d e d i n 1 9 7 4 .

A f t e r t h e f i r e , n e a r l y 40 p e r c e n t o f t h e ground cove r was s t i l l a l i v e i n t h e l i g h t l y burned s t a n d . Th i s r e s i d u a l v e g e t a t i o n developed r a t h e r r a p i d l y , e s p e c i a l l y i n t h e summer o f 1974, s o t h a t t h e r e was 7 0 - p e r c e n t cove r by August 1974. Un l ike t h e h e a v i l y burned s t a n d , many moss and l i c h e n s p e c i e s o f t h e o r i g i n a l s t a n d p e r s i s t e d a f t e r t h e f i r e , and t h e cove r s l o w l y i n c r e a s e d . I n a d d i t i o n , t h e moss cove r has been augmented by t h e growth and s p r e a d o f Ceratodon purpurea . A l l t h e CZadonia s p e c i e s o f l i c h e n s s u r v i v e d t h e l i g h t b u r n , whereas none s u r v i v e d t h e heavy b u r n . I t a p p e a r s t h a t t h e l i g h t l y burned s t a n d w i l l r e t u r n t o i t s o r i g i n a l c o n d i t i o n much more r a p i d l y t h a n t h e h e a v i l y burned s t a n d .

3 . - - A S - 1 B and AS-1C a r e a h e a v i l y burned s t a n d and an unburned c o n t r o l i n a spen i n p l o t s e t 4 ( t a b l e 2 ) .

The h e a v i l y burned s t a n d showed a v e r y r a p i d r e v e g e t a t i o n r a t e , e s p e c i a l l y i n t h e development o f r o o t s u c k e r s ( t a b l e 8 ) . The 1st y e a r a f t e r t h e f i r e (1972) , t h e r e were n e a r l y 200,000 aspen s h o o t s p e r h e c t a r e ; t h i s dropped t o 130,000 i n 1973 and t o 8 ,125 p e r t a b l e 8 i n 1974. S e v e r a l o t h e r t r e e s p e c i e s p r e s e n t b e f o r e t h e b u r n - - b l a c k s p r u c e , w h i t e s p r u c e , and pape r b i r c h - - h a v e n o t d e v e l - oped s e e d l i n g s s i n c e t h e f i r e .

The number o f t a l l s h r u b s i n c r e a s e d r a p i d l y because Rosa a c i c u Z a r i s s p r e a d from s tem and r o o t s h o o t s . The low s h r u b s , a l t h o u g h having a n 1 1 - p e r c e n t cove r i n t h e unburned c o n t r o l , had l e s s t h a n 1 - p e r c e n t cove r 2 y e a r s a f t e r t h e f i r e .

Table 9--Analysis of vege ta t ion i n heav i ly burned ( B S - 2 ~ ) and l i g h t l y

con t ro l s tand (BS-2C) i n lower s lope black spruce

I Density 1

- - - - - - - - - - - -Number of stems per hectare- - - - - - - - - - - Trees : Picea mariana--

Live t r ee s 0 0 0 0 697 65 64 61 1,803 Dead t r ee s 4,431 4,739 4,149 4,089 362 1,075 1,161 2,161 0 Live saplings 0 0 0 0 1,896 62 62 62 2,593

Species

Seedlings 0 19,750 17,750 21,375 4,375 28,250 32,125 38,875 23,250

Tall shrubs: Salix pulchra 125 1,500 125 1,375 500 2,250 1,250 2,125 3,125 Betula glandulosa 125 1,625 750 1,625 1,125 4,500 1,750 3,375 10,750 Rosa acicularis 0 625 125 375 0 0 0 0 0

Total t a l l shrubs 250 3,750 1,000 3,375 1,625 6,750 3,000 5,500 13,875

- - - - - - - - - - - - - - -Cover (percent)- - - - - - - - - - - - - - - Low shrubs:

Vaccinium uliginosum 0.10 1.00 0.70 0.70 2.50 3.80 3.05 5.10 13.85 Ledum groenlandicum .10 1.15 1.40 2.10 2.15 2.65 1.35 4.15 6.55 Vaccinium vitis-idaea .05 .50 .30 .90 3.45 3.55 1.65 6.10 20.35 Spiraea beauverdiana 0 .20 0 . lo 0 0 0 0 0 Ledum decumbens 0 0 .05 .15 1.45 1.05 1.90 1.30 3.10 Oxycoccus microcarpus 0 0 0 0 3.80 3.90 .75 1.75 2.20 Empetrum nigrum 0 0 0 0 1.40 1.10 .90 1.25 1.90

Total low shrubs .25 2.85 2.45 3.95 14.75 16.05 11.15 19.65 47.95

Herbs : Calamagrostis canadensis .65 1.35 2.15 4.40 .70 1.50 1.45 5.15 2.20 Rubus chamaemorus .45 1.0 1.35 2.45 1.90 3.65 2.80 7.35 7.10 Petasites frigidus .10 .40 .15 .25 .20 .45 .10 .80 .70 Equisetum sylvaticum 0 3.35 3.60 8.95 .10 2.65 2.60 5.70 1.25 Cornus canadensis 0 . lo .15 .20 0 0 0 0 0 Epilobium angustifolium 0 .05 . lo .45 0 0 .55 . lo 0 Equisetum arvense 0 0 0 .95 0 0 0 0 0 Equisetum scirpoidea 0 0 0 0 0 0 0 0 1.10 Eriophorum vagina tum 0 0 0 0 . l o .20 .60 0 .05 Pyrola secunda 0 0 0 0 0 0 0 0 .05 Unknown herb 0 0 0 0 .05 .05 0 0 0 Pedicularis labradorica 0 0 0 0 0 0 0 .25 0

Total herbs 1.20 6.25 7.55 17.65 3.05 8.50 7.50 19.95 12.45

Mosses and lichens: Polytrichum sp. .05 1.00 2.80 2.05 1.40 1.70 1.55 5.30 3.65 Fungi 0 .15 .15 .05 0 .25 .10 .35 . 95 Marchantia polymorpha 0 . lo . lo .35 0 0 0 0 0 Other mosses 0 .10 .10 .65 0 0 .10 1.85 Ceratadon purpureus 0 0 2.40 8.05 0 0 .10 1.75 .20 Sphagnum spp . 0 0 -05 0 11.65 12.20 7.30 13.50 36.00 Ptilium crista-castrensis 0 0 0 .05 0 0 .50 0 0 Peltigera spp. 0 0 0 .05 0 0 0 0 0 Aulacomnium palustris 0 0 0 .05 .d5 1.65 3.75 2.85 14.65 Pleurozium schreberi 0 0 0 0 3.70 5.25 7.45 2.05 27.00 Hylocomium splendens 0 0 0 0 .05 0 0 1.75 4.70 Peltigera canina 0 0 0 0 0 .25 0 .65 3.40 Nephroma arcticum 0 0 0 0 0 . l o 0 . lo 3.10 Cladonia sylvatica 0 0 0 0 0 .10 0 .20 2.60 Peltigera aphthosa 0 0 0 0 0 .80 0 0 1.95 Cladonia spp. 0 0 0 0 .05 .30 .25 .50 2.05 Dicranum sp. 0 0 0 0 0 . lo 0 .05 1.05 Cetraria spp. 0 0 0 0 .15 .20 .15 0 .95 Parmelia spp. 0 0 0 0 .1O .25 .05 .10 .85 Cladonia amaurocraea 0 0 0 0 0 .95 .35 0 .40 Cladonia rangiferina 0 0 0 0 0 .35 .05 .25 .05 Aulacomnium turgidum 0 0 0 0 0 0 0 0 .20 Cetraria islandica 0 0 0 0 0 0 0 0 .40 Unknown foliose lichen 0 0 0 0 0 0 0 0 0 Cetraria pinastre 0 0 0 0 0 0 0 0 .10 Other liverworts 0 0 0 0 0 0 0 0 .05

Total mosses and lichens .05 1.35 5.50 10.75 19.95 23.60 21.45 30.45 106.05 Total ground cover 1.45 10.45 15.50 32.35 37.75 48.15 40.10 70.05 166.45

Heavy burn

1971

Light burn

1972 Control 1971 1973 1972 1974 1973 1974

burned (BS-2L) s t ands and i n an adjacent unburned

f o r 4 yea r s a f t e r a '1971 w i l d f i r e

- - - - - - - - - - -Square meters per hectare- - - - - - - - - - -

Basal a rea (m2/ha o r frequency ( percent )

- - - - - - - - - - -Square meters per hectare- - - - - - - - - - -

Heavy burn

1971

Light burn

1972 Control 1971 1973 1972 1974 1973 1974

' i g u r e 1 3 . - -Heavi ly burned b l a c k s p r u c e s t a n d (BS-3H) 1 year a f t e r t h e f i r e (Augus t 1972) shows some d e v e l - opment of Epilo- bium angustifolium L. and Calamagros- tis canadensis.

gure 1 4 . - - L i g h t l y burned b l a c k s p r u c e s t a n d 1 year a f t e r t h e f i r e (Augus t 1972) shows t h e v e r y c o n s p i c u o u s d e v e l - opment o f Equiseturn sylvaticum.

In c o n t r a s t , b o t h t h e herbaceous l a y e r and t h e moss and l i c h e n cove r i n c r e a s e d r a p i d l y u n t i l , i n 1974, t h e y occupied t h r e e t imes t h e a r e a i n t h e burned s t a n d t h a t t h e y d i d i n t h e unburned c o n t r o l . I t i s t o be expec ted t h a t , a s t h e d e n s i t y o f t h e canopy i n c r e a s e s and l e a f l i t t e r accumula te s , t h e cove r o f mosses w i l l be r educed .

The r e s u l t s o f t h e c l u s t e r a n a l y s i s f o r t h e 11 s t a n d s f o r t h e f i r s t 2 y e a r s a f t e r t h e f i r e a r e shown i n f i g u r e 15 . For pu rposes o f t h i s a n a l y s i s , a s t a n d was c o n s i d e r e d new each t ime i t was resampled . A t t h e h i g h e s t l e v e l o f w i t h i n - g r o u p d i s p e r s i o n a l l

WITHIN GROUP DISPERSION (percent)

STANDS AND DATES SAMPLED BS-ZH JUNE 1972

BS-1H JUNE 1972

BS-2H AUG. 1971

8s-1H AUG. 1971

BS-3H JUNE 1972

BS-3H AUG. 1971

AS-1B AUG. 1972

BS-2L AUG. 1971

BS-1L AUG. 1971

BS-2L JUNE 1972

BS-1L JUNE 1972

BS-2L AUG. 1972

BS-1L AUG. 1972

BS-2H AUG. 1972

BS-1H AUG. 1972

BS-3H AUG. 1972

AS-1C AUG. 1972

BS-2C AUG. 1971

BS-3C AUG. 1971

BS-1C AUG. 1971

BS-4C AUG. 1972

Figure 15 . --Resul t s o f a n a l y s i s o f c l u s t e r s o f v e g e t a t i o n d a t a (based o n t w e n t y 1-m2 p l o t s ) c o l l e c t e d i n 11 sample s t a n d s over a 2-year per iod a f t e r t h e 1971 Wickersham Dome f i r e . F o r t h e w i th in -group d i s p e r s i o n , a s t a n d was t r e a t e d a s a new s t a n d e a c h t i m e it was sampled. Burned s t a n d s were sampled i n August 1971 , June 1972 , and August 1972; unburned c o n t r o l s were sampled on1 y once.

stands were combined into one group. At the next level the stands were separated into two groups which contained all the burned stands in one group and all the unburned control stands in the other (fig. 15, group 2 and 3). Within the control group, the aspen stand is different from all the black spruce stands (group 4). Within the black spruce types, the most similar are two stands on the west-facing slope, one at midslope and the other at the base of the slope. The ridgetop stand (BS-3H) was most similar to the east-facing stand (BS-2H) on the lower slope.

The two lightly burned stands (BS-1L and BS-ZL) are more similar to each other at each analysis time than they are to themselves at different sampling times (fig. 15). Also, there is a tendency for the stands to become more similar to each other as time passes. Thus, in August 1971 the within-group dispersion between the two lightly burned stands was 34 percent; in June 1972 it was 10 percent and in August, 5 percent. The same tendency holds true for the heavily burned stands in the bottom of the valley (BS-1H and BS-2H). In August 1971 the within-group dispersion for these two stands was 31 percent; in June 1972 it was 7 percent and in August, only 3 percent.

At the last sampling of the heavily burned stands in August 1972, these stands were grouped with the lightly burned stands rather than with the heavily burned stands from the two earlier inventories.

This tendency for the stands to become more similar as time progresses indicates that the effects of the differences in intensity of burn rapidly become less as the stands develop mature vegetation. We will follow this trend over the next few years.

Plant biomass, obtained on a unit area basis, is often a better indication of amounts and proportions of plant species than are some other measurements, such as basal area, density, or cover. Also, it is essential to know the actual amounts of biomass--usually in units of grams per square meter, kilograms per hectare, or metric tons per hectare--as inputs for studiek of ecosystem processes, such as primary productivity, decomposition, or simply the flow of any nutrient through the system.

In our fire succession studies, we are interested in biomass for several reasons. Increased primary productivity has always been assumed to be one result of fire in the taiga. According to this hypothesis, a release of nutrients held in the organic layers and an increase in soil temperature result in increased activity of soil organisms and assimilation of nutrients by plant roots.

13~his section was prepared by L. A. Viereck, Principal Plant Ecologist, and M. J. Foote, General Biologist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

One way to investigate productivity in successional stands is to record the biomass each year and then determine the amount of increase or decrease in each category. Coupled with this, the amount of biomass discarded by the plants each year--i.e., the litter fall--should also be determined.

At the Wickersham Dome fire study site, we established a minimum program of collection of the aboveground biomass. In 1972, biomass was determined for only one stand, the heavily burned black spruce stand on the ridgetop (BS-3H). In 1973, sampling was expanded to two more heavily burned black spruce stands (BS-1H and BS-2H) in the Cushman Creek Valley and a heavily burned aspen stand (AS-1B). In addition, the ynburned control on the ridgetop (BS-3C) was sampled. Ten 1-m plots were systematically located adjacent to the 20 permanent vegetation plots. All herbaceous plants, low shrubs, mosses, and lichens were clipped at ground level. The material was separated by species, ovendried, and weighed. Because of the scattered and clumped nature of the developing vegetation after the fire, the use of 10 plots resulted in low frequencies for many species and an unreliable statistical sampling. Investi- gations in future studies should use more, smaller plots.

For the large shrub species on the ridgetop plots (BS-3H and BS-3C) , a different method was used; 50 stems were collected adjacent to the plot and an average dry weight of stems and leaves was obtained. This was then multiplied by the number of shrubs per hectare, as determined by sampling the vegetation plots, to give the weight per hectare.

Detailed biomass figures for two sets of stands are given in tables 10 and 11 and figure 16. Table 10 compares the heavily burned black spruce stand, BS-3H, for the first 3 years after the fire with comparable figures for the unburned control. Only low shrubs, herbs, grasses, mosses, and lichens are shown. In addition to the biomass in grams per square meter, the frequency in percent for each species in the 10 plots is given.

There was a slow but steady increase in the total biomass of vegetation developing after the 1971 fire. At first, the aboveground live biomass was zero or close to it, since the fire was hot enough to kill all the aboveground material. For the 1st year, the biomass was primarily shrubs, especially Labrador-tea and prickly rose (table 10). These shrubs sprouted from surviving rootstocks and continued to develop slowly so that by the end of the third summer, their biomass was close to that of the low shrubs in the unburned controls. The herbs and grasses, especially bluejoint (CaZamagrostis canadensis) (Michx.) Beauv. and fireweed, developed more slowly but by the end of 1974 accounted for more than one-half of the biomass. In contrast, the herbs and grasses in the unburned control made up an almost insignificant part of the biomass. The moss and lichen mat, totally destroyed by the fire, was slow to develop. Two mosses and one liverwort (Poly- trichum juniperinurn, Ceratodon purpureus, and ~archantia polymorpha), considered fire species, have developed slowly. None of the mosses present before the fire, such as ~yZocomiurn splendens (Hedw.) B.S.G. and PZeurozium schreberi, (Brid.) Mitt. were recorded in the burned stand. Likewise, no lichens were present, although they made up nearly one-third of the biomass of the unburned control.

'Fable 10--Biomass of low shrubs, herbs, mosses, and l ichens of a heavily burned stand (BS-3H) and an unburned cont ro l i n black spruce on the r idgetop, Wickersham Dome f i r e a rea , f i r s t 3 summers a f t e r the 1971 f i r e

Ledum groenlandi cum Calamagrostis canadensis Rosa acicularis Vaccini um uliginosum Polygonum alaskanum Equisetum sylvaticum

Species

Rubus chamaemorus Cornus canadensis Polytrichum juniperinum

Biomass

Vaccinium vitis-idaea Epilobium angustifolium Spiraea beauverdiana

Frequency

Marchantia polymorpha Geocaulon 1 ividum

Control 1972 1972

Ceratodon purpureus Pleurozium schreberi Nephroma arctica Cladonia spp. Hylocomium splendens Dicranum sp . Cetraria islandica Peltigera aphthosa Lycopodium annotinum Empetrum nigrum Aulacomnium palustre

1973 1973

Drepanocladus sp. Other mosses

Total low shrubs Total herbs and grasses Total mosses Total l ichens

Total Annual increment

1974

-Percent of 10-m2 p lo t s - - 90 80 70 80 80 80 80 0 30 40 20 0 90 70 60 100 10 0 0 0 50 50 50 0 10 10 10 0 20 30 30 10 60 60 40 80 50 50 60 90 10 40 60 0 10 0 0 0 0 10 10 0 0 10 0 0 0 10 20 0 0 0 0 100 0 0 0 70 0 0 0 70 0 0 0 80 0 0 0 60 0 0 0 60 0 0 0 20 0 0 0 30 0 0 0 40 0 0 0 10 0 0 0 10 0 0 0 10

1974

- -Grams per square meter- -

Control

Table 11--Biomass of Scouler willow (salix scouleriana) 1/ i n a heavily burned black spruce stand-

Leaves (g/stem) 5.1 14.1 20.0 Wood (g/stem 6.2 36.8 66.4 Total (g/stem)

2 11.3 50.9 86.3 Stem dens i t 3 (number'm )

.8520 1.525 -9875 Leaves (g/m 4.3 21.5 19.7 wood (e/m2) 5.3 56.2 65.5 Total (g/m2) 9.6 77.6 85.2 Annual increase ( g/m2 9 -6 68.0 7.6

Plant component

y ~ a s e d on density of shrubs from vegetation survey and average weights of 50 stems collected adjacent to the stand.

1972 1973 1974

Figure 1 6 . --Biomass o f a heav i ly burned b l a c k s p r u c e s tand (BS -3H) f o r 4 years a f t e r the 1971 f ire.

Table 11 shows the development of the biomass of the Scouler willow in the same stand. After the fire, the willows developed entirely from stump shoots--four to six times as many stems as had been growing previously. In spite of having been trimmed to the ground by snowshoe hares in the fall of 1971, they produced 11 g of biomass per stem in 1972. This increased, so that by the end of 1974, each stem averaged 86 g, about one-fourth of which was leaves and the rest woody material.

On an area basis, there was a rapid increase iy biomass of the willows, especially between 1972 and 1973--68 g/m (table 11). Between 1973 and 1974, there was a reduction in the number of stems per hectare because of overcrowding and thinning within the individual clumps. Therefore, the biomass increment slowed down (to 7.6 g/mZ). Figure 16 shows graphically the increase in biomass in this stand for the 3 years after the fire.

The development of biomass in the burned aspen stand has been large compared with that in the black spruce stand. Approximately 60 percent of the biomass in the burned aspen stand is from aspen shoots (table 12). Fire moss (Ceratodon purpureus) and liverwort (Marchantia polymorpha), however, have also developed and spread, as well as fireweed and blue joint, resulting in a large annual increment in spite of heavy cropping by moose and snowshoe hare. In the winter of 1972-73, every aspen stem was clipped at snow level; however, this heavy browsing seemed to have little effect on shoot growth the following summer and seemed to encourage the development of lateral branches. This very high production of browse on a good site illustrates the value of fire in the production of wildlife habitat.

Table 13 shows the biomass in the four heavily burned stands and gives a rough indication of the annual net increment of the

Table 12--Biomass of a heavily burned aspen stand (AS-1B) during the 2d and 3d summers after a June 1971 wildfire

Ceratodon purpureus Epilobium angustifolium Corydalis sempervirens Calamagrostis canadensis Rosa acicularis Marchantia polymorpha Cornus canadensis Polytrichum sp, Rubus chamaemorus Picea mariana Fungi Viburnum edule

Total - mosses, herbs, and shrubs Populus tremuloides: Leaves Stems

Total Total for stand Annual increment

Species

Percent in I-m2 plots

Biomass

Grams per sauare meter

1973

Frequency

Table 13--Total biomass in four heavily burned stands at 1/ the Wickersham Dome fire site, 1972-74-

1974 1973 1974

Grams per square meter

Stand

BS-2H : Standing crop Annual increment BS-3H : Standing crop without Salix Annual increment without Salix Standing crop with salix21 Annual increment with Salix 3s-1H: Standing crop without moss Annual increment without moss Standing crop with moss.?/ Annual increment with moss AS-1B : Standing crop Annual increment

1/ - -- = no data.

'~ncludes Salin scouleriana sampled by average weight and density.

Biomass

'~ncludes unburned sphagnum clumps.

1974 - 1972 1973

biomass f o r each s t a n d . I n c r e a s e i n biomass i n t h e t h r e e b l a c k s p r u c e s t a n d s was ex t r eme ly low compared w i t h t h e more p r o d u c t i v e a spen s t a n d . Even i n t h e r i d g e t o p s t a n d (BS-3H) where t h e growth o f SaZix scouZerCana was r a p i d , p r o d u c t i o n was n o t h i g h on an a r e a b a s i s because t h e d e n s i t y o f t h e o r i g i n a l clumps was low. P r o d u c t i v i t y i n t h e two lowland b l a c k s p r u c e s t a n d s was low. I n s t a n d BS-2H, 3 y e a r s a f t e r t h e f i r e , t h e biomass was o n l y 33 g / m 2 . Th i s a r e a was t h e most h e a v i l y bu rned , and n e i t h e r f i r e w e e d n o r CaZamagrost is h a s developed e x t e n s i v e l y ; growth o f s h r u b s , p r i - m a r i l y r e s i n b i r c h ( ~ e t u Z a gZanduZosa Michx.) and L a b r a d o r - t e a , h a s a l s o been s low.

I n s t a n d BS-1H t h e r e were many Sphagnum mounds t h a t d i d n o t r n . These have been growing s l o w l y s i n c e t h e f i r e . For t h i s and , two biomass f i g u r e s a r e g i v e n ( t a b l e 13) - - i n c l u d i n g t h e ss biomass and e x c l u d i n g i t - - s i n c e t h e Sphagnum d i d n o t deve lop om z e r o aboveground biomass a s t h e o t h e r s p e c i e s have . The

biomass f o r BS-3H i s shown w i t h and w i t h o u t S c o u l e r wi l low because t h i s was t h e o n l y b l a c k s p r u c e s t a n d t o deve lop an e x t e n s i v e t a l l sh rub l a y e r .

Litter Fall1'

Annual l i t t e r f a l l , t h e p l a n t m a t e r i a l t h a t f a l l s t o t h e ground each y e a r , has been shown t o be c l o s e l y r e l a t e d t o p r o d u c t i v i t y i n many ecosys t ems . Many s t u d i e s o f l i t t e r f a l l have been made th roughou t t h e wor ld . Any s t u d y o f p r imary p r o d u c t i v i t y w i t h i n an ecosys tem must have i n f o r m a t i o n on l i t t e r f a l l t o d i s t i n g u i s h g r o s s and n e t p r imary p r o d u c t i o n . Knowledge o f l i t t e r f a l l - - h o w m a t e r i a l moves from t h e l i v i n g , aboveground biomass i n t o t h e s o i l o r g a n i c l a y e r s - - i s a l s o e s s e n t i a l i n s t u d i e s o f t h e f low of n u t r i - e n t s and t h e p r o c e s s o f decomposi t ion .

A t t h e Wickersham Dome f i r e a r e a , samples of l i t t e r f a l l were c o l l e c t e d i n b o t h burned and unburned s t a n d s . The o b j e c t i v e was t o de te rmine d i f f e r e n c e s i n t h e p r o d u c t i o n o f l i t t e r a s t h e v e g e t a t i o n deve lops and t o compare c h a r a c t e r i s t i c s o f l i t t e r i n burned s t a n d s w i t h t h o s e i n unburned s t a n d s .

Ten l i t t e r t r a y s were p l a c e d i n each s t a n d . The m a t e r i a l from t h e t r a y s was c o l l e c t e d a t t h e b e g i n n i n g and end of each summer s e a s o n . T h i s m a t e r i a l was s e p a r a t e d by s p e c i e s and p a r t s and t h e n o v e n d r i e d . F i n a l r e s u l t s were e x p r e s s e d a s grams p e r s q u a r e m e t e r .

I n June 1972, 70 t r a y s were p l a c e d i n seven b l a c k s p r u c e s t a n d s : t h r e e h e a v i l y burned s t a n d s (BS-lH, BS-2H, and BS-3H), two l i g h t l y burned s t a n d s (BS-1L and BS-2L), and two unburned s t a n d s (BS-2C and BS-3C). I n June 1973, 30 t r a y s were s e t o u t i n t h r e e o t h e r s t a n d s : a h e a v i l y burned a spen s t a n d (AS-lB), an unburned a spen s t a n d (AS-lC), and an unburned b l a c k s p r u c e s t a n d (BS- 4C) .

14~his section was prepared by L. A. Viereck, Principal Plant Ecologist, and M. J. Foote, General Biologist, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Institute of Northern Forestry, Fairbanks, Alaska.

O r i g i n a l l y , t h e f a l l c o l l e c t i o n was t o be made a f t e r t h e y e a r ' s l e a f f a l l . In 1972 and i n 1974, however, t h e f i r s t snow came b e f o r e l e a f f a l l was complete, making i t imposs ible t o o b t a i n a complete f a l l c o l l e c t i o n of l i t t e r . There fo re , f u t u r e c o l l e c t i o n s w i l l be made only i n t h e s p r i n g a f t e r snowmelt. A l l d a t a w i l l be summarized from June of one y e a r t o June o f t h e nex t y e a r .

Small (1/4-m2) t r a y s a r e inadequate f o r sampling l a r g e l i t t e r , such a s branches o r whole t r e e s . To o b t a i n some i d e a of t h e l a r g e l i t t e r i n t h e burned s t a n d a t r i d g e t o p s t a n d BS-3H, we e s t a b l i s h e d a s e r i e s of f i v e 10-m2 p l o t s . A l l l o o s e l i t t e r l a r g e r than 1-cm diameter was removed i n June 1972. Each suc- ceeding y e a r t h e l i t t e r was c o l l e c t e d from t h e s e p l o t s and weighed.

A summary of t h e t o t a l l i t t e r f a l l f o r each s t a n d , a s we l l a s an average f o r burn c a t e g o r i e s , i s shown i n t a b l e 14. In t h e unburned b l a c k spruce s t a n d s l i t t e r f a l l was low, amounting t o approximate ly 1 0 g / m 2 p e r y e a r .

Table 14--Litter f a l l i n burned and unburned stands f o r 3 years a f t e r t he 1971 Wickersham Dome f i r e

- - - - - - - - -Grams per square meter- - - - - - - - - BLACK SPRUCE

Heavily burned: BS-1H -- 5.12 5.12 2.08 0.44 2.52 BS-2H -- 3.64 3.64 1.76 .08 1.84 BS-3H 8.84 3.16 12.00 3.36 2.68 6.04

Average 6.92 3.47 Lightly burned:

BS-1L 14.40 4.48 18.88 6.48 2.20 8.68 BS-2L -- 21.04 21.04 1.08 2.24 3.32

Average 19.96 6.00 Unburned control: BS-2C -- 5.32 5.32 4.64 .48 5.12 BS-3C 4.60 9.40 14.00 13.80 3.24 17.04

Average 9.66 11.08

Stand

ASPEN Heavily burned:

AS-1B 2/ -- -- 108.84 8.72 - 117.56 Unburned control:

AS-1C 2/ -- -- 153.40 22.96 - 176.36 --

I/-- = negl ig ib le amount. - ' ~ i t t e r t r ays were not s e t out u n t i l June 1973.

Collection period

June t o Sept . 197&

Oct. 1972 t o

June 1973

June 1972 t o

June 1973

J u n e t o Sept . 1973

Oct.1973 t o

June 1974

Year, J,,1973

t o 1974

L i t t e r f a l l i n t h e burned b lack spruce s t a n d s o r i g i n a t e d p r i - m a r i l y from dead s t a n d i n g t r e e s and from wil lows. L i t t e r from t h e low shrubs and he rbs was l o c a l i z e d ; s t a t u r e o f t h e s e p l a n t s i s o f t e n t o o low t o a l low d e p o s i t i o n i n t h e t r a y s . L i t t e r f a l l i n the l igh t lyburned a r e a s was h e a v i e s t t h e second summer a f t e r t h e f i r e ; i t dropped o f f dur ing t h e 3d y e a r . L i t t e r f a l l i n t h e h e a v i l y burned s t a n d s fo l lowed a s i m i l a r p a t t e r n bu t was l e s s abundant compared wi th t h a t i n t h e l i g h t burn . Most of t h e need les and smal l branches and cones were n o t consumed i n t h e l i g h t l y burned s t a n d s , whereas i n t h e h e a v i l y burned s t a n d s they e i t h e r were consumed o r dropped t o t h e ground t h e f i r s t summer.

The r a t e of l i t t e r f a l l i s expected t o a c c e l e r a t e a s t h e bark begins t o s lough o f f t h e s t a n d i n g dead t r e e s and a s smal l branches and cones f a l l . Even tua l ly , a s t h e shrubs become l a r g e r and more numerous and when t h e developing sp ruce s e e d l i n g s become t a l l e r , t h e l i t t e r f a l l r a t e should i n c r e a s e t o a t l e a s t t h a t of t h e unburned s t a n d .

I n t h e burned aspen s t a n d , l i t t e r p roduc t ion was r e l a t i v e l y h i g h , 118 g /m2 p e r y e a r , because of r a p i d development of t h e aspen sucker s h o o t s . Growth of t h e s e s h o o t s was so r a p i d i n 1974 t h a t t h e l i t t e r i n t h e 1974-75 c o l l e c t i o n y e a r may n e a r l y equal t h a t of t h e unburned c o n t r o l s .

The l a r g e l i t t e r , 1-cm diameter and l a r g e r , was sampled i n only one h e a v i l y burned b lack spruce s t a n d . The o r i g i n a l q u a n t i t y of l a r g e l i t t e r i n t h e s e p l o t s when they were e s t a b l i s h e d i n t h e summer of 1972 was 218 g / m 2 ( range 19 $0 614) . A second c o l l e c t i o n i n September 1973 y i e l d e d on ly 4 . 3 g / m (range 1 t o 8 . 2 ) . Col- l e c t i o n s w i l l be cont inued on a y e a r l y b a s i s .

Litter Decompo~ition~~

To determine r e l a t i v e r a t e s of l i t t e r decomposit ion, we e s t a b - l i s h e d a s e r i e s of l i t t e r b a g s i n two h e a v i l y burned s t a n d s and two unburned c o n t r o l s i n t h e f a l l of 1972. These bags were t o be c o l l e c t e d over a p e r i o d of 5 y e a r s and t h e i r c o n t e n t s analyzed.

Three s p e c i e s were used f o r t h e l i t t e r . Needles were c o l l e c t e d from b lack sp ruce growing on t h e s i t e , and 20-g samples were p laced i n 30- by 30-cm nylon mesh bags . Leaves were c o l l e c t e d from both bog b l u e b e r r y and Labrador - t ea ; 5 -g samples of each were p laced i n nylon mesh bags measuring 15 cm on each s i d e .

The s e r i e s was repea ted f o u r t imes a t each s t a n d . A t each s i t e e i g h t bags f o r each s p e c i e s were s t a p l e d t o a wi re running a long t h e ground. In a l l , 32 bags f o r each s p e c i e s were p laced i n each s t a n d . C o l l e c t i o n s were made twice y e a r l y , i n s p r i n g and l a t e f a l l , f o r t h e nex t 3 y e a r s and i n t h e f a l l on ly f o r t h e fo l lowing

I d

This s e c t i o n was prepared by L . A. Viereck, P r inc ipa l P lant Ecologis t , and M. J . Foote, General B io log i s t , USDA Forest Serv ice , P a c i f i c Northwest Forest and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

2 y e a r s . The f i r s t c o l l e c t i o n s were made i n May 1973. The samples were analyzed i n t h e l a b o r a t o r y and r e s u l t s compared wi th d a t a on o r i g i n a l weight and n u t r i e n t c o n t e n t .

Table 15 summarizes t h e weight l o s s of t h e l i t t e r b a g s f o r t h e f i r s t 2 y e a r s a f t e r t h e bags were p laced i n t h e s t a n d s . Losses of biomass f o r t h e sp ruce need les and Labrador - t ea l e a v e s a r e s i m i l a r , 30-31 p e r c e n t . The b l u e b e r r y l e a v e s l o s t s l i g h t l y more we igh t , about 37 p e r c e n t . As would be expected, t h e weight l o s s was more r a p i d dur ing summer than w i n t e r . There was no a p p r e c i a b l e d i f f e r e n c e i n weight l o s s between t h e l i t t e r b a g s i n t h e burned s t a n d s and t h o s e i n t h e unburned c o n t r o l s .

Table 16 summarizes t h e n u t r i e n t c o n t e n t of t h e o r i g i n a l sample (based on two a n a l y s e s ) and of t h e samples from May and September 1973. A t t h e time we wrote t h i s r e p o r t , t h e a n a l y s e s of t h e 1974 c o l l e c t i o n s were n o t complete, and any conc lus ions about d i f f e r - e n t i a l r a t e s of n u t r i e n t l o s s between t h e t h r e e l i t t e r samples o r between t h e burned s t a n d and unburned c o n t r o l would be premature .

In a d d i t i o n t o a n a l y s i s of t h e major n u t r i e n t s , t h e samples were analyzed f o r l i g n i n , a c i d d e t e r g e n t f i b e r , and ash c o n t e n t ( t a b l e 1 7 ) . In g e n e r a l , p e r c e n t of weight l o s s of l i g n i n from l i t t e r b a g m a t e r i a l has been found i n v e r s e l y r e l a t e d t o t h e i n i t i a l c o n t e n t of l i g n i n . U n f o r t u n a t e l y , t h e o r i g i n a l samples were no t analyzed f o r t h e s e t h r e e s u b s t a n c e s . There was probably no s i g n i f - i c a n t change, however, i n l i g n i n c o n t e n t t h e f i r s t winter - -August 1972 u n t i l l a t e A p r i l 1973. Spruce n e e d l e s , w i t h a l i g n i n c o n t e n t o f 14-18 p e r c e n t , would be expected t o decompose more r a p i d l y than b l u e b e r r y l e a v e s w i t h a l i g n i n c o n t e n t of 26-32; b u t weight l o s s d a t a i n d i c a t e d t h a t b l u e b e r r y l e a v e s decomposed more r a p i d l y than sp ruce n e e d l e s .

A t t h e end of t h i s 5-year s t u d y o f l i t t e r decomposit ion, i t w i l l be p o s s i b l e t o compare decomposit ion r a t e s between t h e burned s t a n d s and t h e unburned c o n t r o l s and among t h e l i t t e r from t h e t h r e e s p e c i e s . I t i s a l s o expected t h a t d i f f e r e n c e s i n t h e r a t e of r e l e a s e of t h e v a r i o u s elements can be compared. The g e n e r a l r a t e of decomposit ion of c o n t e n t s o f t h e l i t t e r b a g s w i l l a l s o be compared wi th t h e c o n t e n t s of t h e l i t t e r b a g s from o t h e r s t u d i e s i n more temperate l o c a t i o n s .

Black Spruce Seed Fall and Seedling Establishment16 Black sp ruce cones a r e s e m i s e r o t i n u s ; t h a t i s , they remain on

t h e t r e e and open s lowly , thus d i s p e r s i n g seed over a p e r i o d of y e a r s . There fo re , provided t r e e s a r e producing s e e d , some seed i s always p r e s e n t on t h e t r e e s (Heinselman 1957) . I f t h e cones a r e no t des t royed by f i r e , t h i s h a b i t makes b l a c k sp ruce w e l l adapted f o r r eseed ing burned over a r e a s . I t i s t h e on ly i n t e r i o r

1 6 ~ h i s sec t ion was prepared by J . C . Zasada, S i l v i c u l t u r i s t , L . A. Viereck, Pr incipal Plant Ecologist , and M. J . Foote, General Biologis t , USDA Forest Service, Pac i f i c Northwest Forest and Range Experiment S ta t ion , I n s t i t u t e of Northern Forestry, Fairbanks, Alaska.

Table 15--Weight l o s s o f l i t t e r b a g s f o r 2 years a f t e r t h e i r i n s t a l l a t i o n i n 1/ burned s tands and t h e i r unburned controls-

- - - -Grams dry weight- - - - --- Percent

L i t t e r

Picea mariana needles: Unburned con t ro l s 20.0 16.9 15.0 14.7 13.8 31.3 Burned s tands 20.0 16.5 14.8 14.4 13.8 31.1 Ledum groenlandicum leaves: Unburned con t ro l s 5.0 4.3 3 .9 3.9 3.5 30.3 Burned s tands 5.0 4.3 3.8 3.7 3.5 30.6

Augs 1972

Vaccinium uliginosum l eve l s : Unburned con t ro l s 5.0 3.9 3.4 3.4 3.2 37 .O Burned s tands 5.0 4.0 3.4 3.5 3.1 37.4

y ~ a c h value is an average o f 8 bags.

May 1973

Table 16--Original ( f a l l 1972) nutrient content of leaves and needles Iin litterbags from burned stands and unburned controls and

the nutrient content a f te r 1 winter and 1 sulomer of decomposition , Wickersham Dane f i r e sitel/

Sept 1973

. . . . . . . . . . . . . . . . . . . . . . . Magnesium:

Unburned stand 0.12 0.184 + 0.035 0.164 + 0.018 0.10 Burned stand .12 .lo5 + .026 .lo5 + .026 .10

Nutrient

Zinc : Unburned stand .0025 .009 + .014 .006 + .004 .0028 Burned stand .0025 . 0 1 3 i .007 .011+ .006 .0028

Man~anese (percent): Unburned stand ,0915 .O9l + .021 -084 * -015 .090 Burned stand .0915 .044 i .009 .NO * .016 .090

Weight loss after 2 years

May 1974

Iron (percent): Unburned stand .010 .017+ .010 .026+ .011 .015 Burned stand ' .010 .020f .006 .024+ .007 .015

Sept 1974

Vaccinium uliginosum leaves

Calcium (percent): Unburned stand .55 . 6 4 4 i .172 .713+ .141 -488 Burned stand .55 .410 f .070 .496 + .129 .488

August 1972

Potassium (percent Unburned stand .65 .253 i .lo8 . l lg + .042 .30 Burned stand .65 . 2 0 6 i .lo2 . l o 3 2 .060 .30

Ledum groenlcrndicum leaves

Phosphorus (percent): Unburned stand .117 .099 i .017 .la t .028 -090 Bursled stand .117 ,107 i .025 ,112 + .021 .090

May 1973 May 1973

Picea mariana needles

Nitrogen (percent): Unburned stand 1.644 .463 i .033 .495 i .063 1.298 Burned stand 1.644 . 5 6 1 i .039 .595+ .On 1.298

September 1973

September 1973 1972

August

c ~ a c h value is based on 8 observations. Plus or minus signs indicate standard error of the mean.

&Y 1973 September 1973

Table 17--Lignin, acid detergent f i b e r , and ash content of leaves and needles from burned s tands and unburned

controls a f t e r 1 winter and 1 summer, Wickersham Dome f i r e s i t e , 1979 '

Lignin : Unburned cont ro l 26.66 + 3.41 34.91 + 1.90 31.55 + 2.70 33.33 + 0.99 14.75 + 2.78 17.65 + 1.06 Burned stand 29.00 + 1 . 9 6 34.67 k 1 . 7 5 32.49 + 1.86 33.05 f 1 . 0 2 1 7 . 8 6 2 2 . 0 2 19.14 k 2 . 2 8

Acid detergent f i be r : Unburned cont ro l 47.02 + 3.09 59.04 + 1.73 52.91 + 2.59 56.82 + 2.39 35.96 + 2.23 40.34 + 1.80 Burned stand 49.86 + 4.42 60.59 2 2.61 54.27 + 1.45 57.28 + 1.90 39.94 + 2.82 42.47 + 3.76

Ash : Unburned cont ro l .91 + .45 -83 + .38 .48 + .28 .45 + .36 .68 + .44 .79 + .39 Burned stand .66 + -29 .54 2 .30 .47 + .25 .57 + .42 .76 ? .43 .57 + .50

Content

1 ' ~ach value is based on 8 observations. Plus o r minus s igns indica te standard e r r o r of t he mean.

eaves contained i n l i t t e rbags . 2'~eedles contained i n l i t t e rbags .

Alaska t r e e s p e c i e s t h a t e x h i b i t s t h i s c h a r a c t e r i s t i c . Other t r e e s p e c i e s d i s p e r s e t h e m a j o r i t y of t h e i r annual c rop over a p e r i o d of a few weeks t o s e v e r a l months (Zasada and Viereck 1970, Zasada 1971; Bjorkbom 1971) .

The o b j e c t i v e s oT t h i s p o r t i o n of t h e s t u d y were t o (1) com- pa re t h e q u a n t i t y and q u a l i t y of seed d i s p e r s e d by t r e e s on s i t e s t h a t burned a t d i f f e r e n t i n t e n s i t i e s , (2) determine t h e annual d i s p e r s a l p a t t e r n i n a burned s t a n d and an unburned c o n t r o l , (3) e s t i m a t e t h e s e e d - s e e d l i n g r a t i o ( t r e e p e r c e n t ) , and (4) e s t i - mate t h e q u a n t i t y and q u a l i t y of seed p o t e n t i a l l y a v a i l a b l e i n t h e cones of t h e r e s i d u a l burned and unburned t r e e s .

We used two types of seed t r a p s t o fo l low seed d i s p e r s a l i n t h r e e burned b ack spruce s t a n d s and one unburned c o n t r o l . Five f l a t t r a p s (1-m4 sampling s u r f a c e a r e a f o r each t r a p l o c a t e d 15 cm above t h e ground s u r f a c e ) were p laced i n a l l s t a n d s i n August 1971. Five t a l l t r a p s (1-m2 sampling s u r f a c e a r e a f o r each t r a p l o c a t e d 1 . 3 m above t h e ground s u r f a c e ) were added i n February 1972.

"actinium ul ig inosud ' ~ i c e a mariana?'

Seeds were c o l l e c t e d monthly from t h e t a l l t r a p s between February 1972 and February 1973. Seeds were c o l l e c t e d from t h e f l a t t r a p s each month dur ing t h e summer and a f t e r snowmelt i n s p r i n g u n t i l e a r l y June 1974. In w i n t e r , t r a p samples o f t e n con ta ined snow which was melted and s t r a i n e d t o remove t h e seed and l i t t e r ; seeds were s e p a r a t e d from t h e l i t t e r i n t h e l a b o r a t o r y . Germination t e s t s were conducted on u n s t r a t i f i e d seeds i n p e t r i d i s h e s a t 2 2 O ~ c o n s t a n t temperature and 18-h days . Any seed showing a c t i v i t y ( e . g . , s p l i t seed c o a t , r a d i c l e emergence) was cons ide red g e r - minated. A l l ungerminated seeds were c u t open and c l a s s i f i e d a s e i t h e r f i l l e d o r empty.

May

Ledum g r o e n l a n d i d /

May

I n August of 1971, 1972, 1973, and 1974 new b l a c k sp ruce seed- l i n g s were counted on twenty 1 - m Z p l o t s i n s t a n d s BS-lL, BS-lH, and BS-3H. These counts were p a r t of t h e v e g e t a t i o n a n a l y s i s , and t h e methods a r e d e s c r i b e d i n t h a t s e c t i o n . Using t h e s e d a t a on s e e d l i n g s and seed f a l l , we e s t i m a t e d s e e d l i n g p e r c e n t (seed- l ings /100 s e e d s ) .

September May September September

So t h a t we c o u l d de te rmine t h e t o t a l amount o f b l a c k s p r u c e s e e d p o t e n t i a l l y a v a i l a b l e w i t h i n t h e b u r n , t r e e s were f e l l e d i n November 1971 and September 1972 and a l l t h e i r cones removed. Seeds were removed from t h e cones a c c o r d i n g t o methods o u t l i n e d by t h e USDA F o r e s t S e r v i c e (1948) . The t o t a l number of s e e d s was de te rmined by c o u n t i n g s e e d s i n f o u r 1 - g subsamples f o r each t r e e and t h e n m u l t i p l y i n g t h a t number o f s e e d s by t h e t o t a l weight o f s e e d f o r t h a t t r e e . Germinat ion t e s t s were conducted on f o u r 100- seed r e p l i c a t i o n s from each t r e e .

Quantity and quality of dispersed seed17

T o t a l s e e d f a l l f o r t h e 2 3 / 4 - y e a r p e r i o d was g r e a t e r i n t h e t h r e e burned s t a n d s t h a n i n t h e unburned c o n t r o l . Because of t h e l a r g e w i t h i n - s t a n d v a r i a t i o n , however, s e e d f a l l f o r o n l y t h e l i g h t burn was s i g n i f i c a n t l y h i g h e r t h a n f o r t h e c o n t r o l (p=0 .05) . During t h e 1s t y e a r o f t h e s t u d y , s e e d f a l l i n a l l burned s t a n d s was s i g n i f i c a n t l y h i g h e r t h a n i n t h e unburned c o n t r o l (p=0 .05) . From September 1972 t o June 1974, t h e amount of s e e d f a l l i n t h e unburned c o n t r o l was s i g n i f i c a n t l y h i g h e r t h a n i n one h e a v i l y b u r n e d . s t a n d b u t n o t s i g n i f i c a n t l y h i g h e r t h a n i n t h e o t h e r two burned s t a n d s ( t a b l e 1 8 ) .

Table 18--Quantity and qua l i ty o f black spruce seed dispersed between September 1971 and June 1974 i n 3 burned s t ands and an unburned

control a t t he Wickersham Dane f i r e sitd'

- - - - - -Number- - - - - - - - - - - - - - - - - - - -pement- - - - - - - - - - - - - - - BS3C, unburned 85 t 14b 132 t 22ab 218 + 33b 46 t 4a 48 * 7ab 47 t 5a 94 t 3a 65 * 10ab 77 t 5ab

BS-lL, l i g h t l y burned 386 t 39a 120 t 20ab 507 t 23a 50 + 2a 53 * 3ab 50 t 2a 87 t 2a 84 * 4a 87 t l a

BS-lH, heavi ly burned 289 * 15a 75 t 9b 364 t 22ab 43 t 3a 56 * 2a 75 * 2b 75 * 2b 58 t 4b 70 * 2bc

BS-3H, heavi ly burned 319 * 64a 142 t l l a 461 + 72ab 42 t 3a 36 * 5b 43 i 2a 68 * 2b 51 t 5b 63 * 2c

Stand

Y v a l u e s followed by t h e same l e t t e r s i n a column d id not d i f f e r s i g n i f i c a n t l y a t t h e pz0.05 l eve l ; p lus or minus signs indicate standard e r r o r o f t h e mean.

--

1 7 ~ h i s s e c t i o n was prepared by J . C . Zasada, S i l v i c u l t u r i s t , 1J. A. Viereck, P r inc ipa l P lant Ecologis t , and M. J . Foote, General B io log i s t , USDA Forest Service, P a c i f i c Northwest Fores t and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

Real germination Total seeds per square meter

Sept . 1971 t o

Sept. 1972

F i l l e d seeds

Total Sept. 1971

t o Sept. 1972

Sept . 1972 t o

June 1974

Sept. 1972 t o

June 1974 Total

Sept . 1971 t o

Sept . 1972 Total

Sept . 1972 t o

June 1974

I n i n t e r p r e t i n g t h e s e d a t a , t h e r e a d e r must r e a l i z e t h a t t h e f l a t s e e d t r a p s were n o t i n s t a l l e d u n t i l abou t 2 months a f t e r t h e f i r e . Thus, t h e amount o f s e e d d i s p e r s e d r e l a t i v e l y soon a f t e r t h e f i r e i s n o t known. Wil ton (1963) r e p o r t e d t h a t abou t 370 b l a c k s p r u c e s e e d s p e r s q u a r e me te r ( 3 . 7 m i l l i o n / h a ) were d i s - p e r s e d i n a 60-day p e r i o d a f t e r an August 25 f i r e i n Newfoundland. He concluded t h a t t h i s was p r o b a b l y l e s s t h a n h a l f t h e a v a i l a b l e s e e d i n t h e s t a n d .

Rea l g e r m i n a t i o n ( t h e p e r c e n t a g e of f i l l e d s e e d s which a c t u a l l y germinated) o f s e e d d i s p e r s e d d u r i n g t h e 1 s t y e a r was g r e a t e s t i n t h e unburned c o n t r o l and t h e l i g h t l y burned s t a n d . For t h e whole s t u d y , r e a l g e r m i n a t i o n i n t h e l i g h t bu rn was s i g n i f i c a n t l y g r e a t e r t h a n i n e i t h e r o f t h e heavy b u r n s ; i n t h e unburned c o n t r o l i t was s i g n i f i c a n t l y g r e a t e r t h a n i n o n l y one o f t h e heavy burns ( t a b l e 1 8 ) . These d a t a s u g g e s t t h a t t h e f i r e may have a f f e c t e d g e r m i n a t i o n . T h i s i s n o t unexpected when t h e b u r n i n g i n t e n s i t y i s c o n s i d e r e d . For example, t h e l i g h t l y burned s t a n d was chosen p a r t i a l l y on t h e b a s i s t h a t a l l o f t h e n e e d l e s were n o t consumed; some t r e e s w i t h g r e e n n e e d l e s even remained a f t e r t h e f i r e . I n c o n t r a s t , t h e n e e d l e s and f i n e b ranches were consumed i n t h e h e a v i l y burned s t a n d s . T h i s i n d i c a t e s t h a t cones on t h e t r e e s i n t h e h e a v i l y burned s t a n d s were s u b j e c t e d t o more i n t e n s e h e a t t h a n t h o s e i n t h e l i g h t l y burned s t a n d . Thus, i t would be expec ted t h a t s e e d q u a l i t y might be a f f e c t e d i n h e a v i l y burned a r e a s .

E s t i m a t e s o f s e e d f a l l o b t a i n e d w i t h t a l l t r a p s were d i f f e r e n t from t h o s e o b t a i n e d w i t h f l a t t r a p s . For t h e same t ime p e r i o d , t h e s e e s t i m a t e s were 450 and 320 s e e d s p e r s q u a r e me te r i n t h e heavy burn f o r t h e t a l l and f l a t t r a p s , r e s p e c t i v e l y , and 147 and 85, r e s p e c t i v e l y , i n t h e unburned c o n t r o l . Because o f v a r i a t i o n from t r a p t o t r a p , however, t h e e s t i m a t e s w i t h i n each burn c a t e g o r y were n o t s i g n i f i c a n t l y d i f f e r e n t ( p = 0 . 0 5 ) . There a r e s e v e r a l r e a s o n s f o r t h e p o s s i b l e d i f f e r e n c e s , and t h e s e s h o u l d be c o n s i d - e r e d i n f u t u r e s t u d i e s of s e e d f a l l . F i r s t , t h e d e s i g n o f t h e f l a t t r a p may have a l lowed t h e wind t o blow some s e e d s o u t of t h e t r a p s . I n f a c t , on windy days movement of s e e d s i n t h e t r a p s was obse rved . I n t h e t a l l t r a p s , on t h e o t h e r hand, t h e s e e d s dropped i n t o a r e c e p t a c l e a t t h e bot tom of t h e t r a p and were n o t a f f e c t e d by wind a f t e r t h e y e n t e r e d t h e t r a p . A second r e a s o n i s t h e d i f f e r e n t sequence o f c o l l e c t i o n : The t a l l t r a p s were c o l l e c t e d weekly and t h e f l a t t r a p s o n l y monthly d u r i n g t h e summer and i n t h e s p r i n g a f t e r snowmelt. Thus , when snow t e m p o r a r i l y cove red t h e t o p s of t h e t r a p s , t h e weekly removal o f t h e snow may have r e s u l t e d i n fewer s e e d b e i n g blown away.

Annual pattern of seed dispersal1''

Seed d i s p e r s a l p a t t e r n s f o r a 1 - y e a r p e r i o d (Februa ry 1972 t o February 1973) f o r one o f t h e heavy burns and t h e unburned c o n t r o l

1 8 ~ h i s s e c t i o n was prepared by J . C . Zasada, S i l v i c u l t u r i s t , L . A. Viereck, P r inc ipa l P lant Ecologis t , and M . J . Foote, General B io log i s t , USDA Fores t Serv ice , P a c i f i c Northwest Forest and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska.

were s i m i l a r . The s e e d f a l l ( t o t a l and f i l l e d s e e d s ) was much g r e a t e r , however, on t h e heavy burn t h a n on t h e unburned c o n t r o l ( f i g . 1 7 ) . These f i n d i n g s s u g g e s t t h a t t h e f i r e d i d n o t a f f e c t t h e annua l d i s p e r s a l p a t t e r n f o r t h e y e a r a f t e r t h e f i r e , b u t i t a p p a r e n t l y r e s u l t e d i n more cones opening ( o r opening more f u l l y ) and d i s p e r s i n g s e e d d u r i n g p e r i o d s o f normal peak d i s p e r s a l i n unburned s t a n d s . The main c o n t r o l l i n g mechanism f o r t h e annua l d i s p e r s a l p a t t e r n i s p r o b a b l y t h e opening and c l o s i n g o f cones i n r e s p o n s e t o changes i n a tmospher i c humid i ty and t e m p e r a t u r e . Th i s i s known t o occur i n S i t k a s p r u c e ( H a r r i s 1969) and w h i t e s p r u c e b u t h a s n o t been obse rved i n b l a c k s p r u c e .

Seeds on t r e e s . - - T h e number o f s e e d s p r e s e n t i n o l d and new cones was h i g h l y v a r i a b l e i n t h e unburned c o n t r o l . New cones ave raged a lmos t t w i c e a s many s e e d s a s o l d c o n e s ; however, o l d cones c o n t a i n e d more t h a n 26,000 s e e d s p e r t r e e ( t a b l e 1 9 ) .

FEB. MARCH APRIL M A Y JUNE JULY AUGUST SEPT. OCT. NOV. DEC. FEE. 1972 1973

150

Figure 17.--Seed f a l l i n burned and unburned b l a c k s p r u c e s t a n d s from February 1972 t o February 1973.

-

I n t h e burned s t a n d , l a r g e q u a n t i t i e s o f s e e d remained on t h e t r e e s 1 y e a r a f t e r t h e f i r e . Because o f t h e l a r g e v a r i a t i o n among t r e e s i n t h e burned and unburned s t a n d s , we canno t draw any con- c l u s i o n s conce rn ing t h e p e r c e n t a g e o f s e e d d i s p e r s e d t h e 1st y e a r .

125 -

a p 100 - S YI LT a

o-----o TOTAL SEED FALL. UNBURNED CONTROL t - 4 FILLED SEEDS, UNBURNED CONTROL

75 - In a

6----4 TOTAL SEED FALL. BURNED STAND &----- 4 FILLED SEEDS. BURNED STAND

W a.

V) a

The r e a l g e r m i n a t i o n p e r c e n t a g e s i n d i c a t e , a s t h e y d i d f o r s eed c o l l e c t e d i n s e e d t r a p s d u r i n g t h e 1 s t y e a r o f t h e s t u d y ( t a b l e 1 8 ) , t h a t f i r e reduced t h e q u a l i t y o f t h e s e e d c o n t a i n e d i n b l a c k s p r u c e cones . Real g e r m i n a t i o n ave raged 90 , 6 5 , and 3 2 p e r c e n t f o r s e e d s c o l l e c t e d from unburned t r e e s and from 1 - and 2 - y e a r - o l d burned t r e e s , r e s p e c t i v e l y . I n t h e unburned c o n t r o l , 6 o f t h e 7 t r e e s ( 8 6 p e r c e n t ) had r e a l g e r m i n a t i o n o f 90 p e r c e n t o r h i g h e r , whereas i n t h e burned sample o n l y 6 of 25 (24 p e r c e n t ) had r e a l ge rmina t ion of 90 p e r c e n t o r h i g h e r ( t a b l e 2 0 ) .

Table 19--Quantity and q u a l i t y o f seed contained i n cones o f burned and unburned b lack spruce t r e e s

Unburned c o n t r o l : Average 2/10 Standard d e v i a t i o n Range

Burned s t a n d , sampled i n 1971:

Average 15 Standard d e v i a t i o n Range

Stand

Burned s t a n d , sampled i n 1972:

Average 10 Standard d e v i a t i o n Range

Number o f sample t r e e s

L/O1d cones appeared t o be o l d e r than 1 o r 2 y e a r s ; new cones were produced i n 1970 and 1971; a l l cones c o l l e c t e d from t h e burned s t a n d s were c l a s s i f i e d a s o l d .

2 /1~ t r e e s were sampled, but on ly 7 had cones.

o l d coned-'

Although the seed testing rules do not recommend stratification for germination trials in black spruce, seed dormancy has not been adequately examined in northern genotypes of this species. Thus, it is possible that some of the poor germination could be the result of seed dormancy. Future tests should include stratification treatments until dormancy patterns are well known.

New cones

Number per t r e e

Seedling establishment.--The success of forest regeneration is determined by seed supply and the biotic and abiotic variables generally referred to as site conditions. Using seedling counts obtained from the vegetation analysis (table 21) and the seed fall data, we can gain some insight into the question of adequacy of seed supply, expressed in seedling percent (seedlings/lOO viable seeds), for these site conditions.

Viable Number of Seedling St and seeds/mZ seed1 ings/m2 percent

BS-1L (light burn) 220 3.9 1.8 BS-1H (heavy burn) 114 1.2 1.0 B S - 3 H (heavy burn) 125 . 3 .2

Seeds per t r e e

Number per t r e e

Seeds per cone

These seedling percents are quite low compared with those reported by Johnston (1972) for black spruce regeneration on various seed bed types in northern Minnesota. Because of the variability associated with both the seed fall and estimates of seedling density, the estimates of seedling percent also have a high degree of variability.

Seeds per cone

Seeds per t r e e

Table 20--Average q u a l i t y o f seed from black spruce trees i n an unburned c o n t r o l and i n a burned s tand sampled twice a f t e r t h e 1971 Wickersham Dome f i r e

Unburned c o n t r o l : 1 2 5 7 8 9

10

Tree number

Mean

Burned s t a n d , sampled i n 1971: 1 2 3 4 5 6 ? 8 9

10 11 12 1 3 1 5 16

Mean

Burned s t a n d s , sampled i n 1972: 18 19 20 21 22 23 24 25 26 27

Real germination F i l l e d seed

Mean

Percent Percent

Germinated seed

Standard dev ia t ion

Standard dev ia t ion Percent Standard

dev ia t ion

Table 21--Average number of seedlings in three burned black spruce stands for 3 years after the 1971 Wickersham Dome fire

Seedlings per square meter

Year

1972 : Standard deviation Range



Stand

Autecology of 1st Year Postfire Tree Regenerationlg

BS-1L

The t y p e o f r e g e n e r a t i o n a f t e r a f i r e i s de te rmined by t h e p e r - c e n t a g e o f t h e o r g a n i c mat consumed ( t h i s d i r e c t l y a f f e c t s s e e d bed c o n d i t i o n s and t h e m a t e r i a l a v a i l a b l e f o r v e g e t a t i v e r e p r o - d u c t i o n ) , t h e a b i l i t y o f t h e p r e b u r n v e g e t a t i o n t o r e p r o d u c e , and t h e s u p p l y o f s e e d w i t h i n o r a d j a c e n t t o t h e bu rn . The o b j e c t i v e s of t h i s s t u d y were t o examine t h e dynamics o f t r e e s e e d g e r m i n a t i o n and f i r s t growing s e a s o n s u r v i v a l on t h e v a r i o u s s e e d beds i n t h e burned s t a n d s , and t o r e c o r d n a t u r a l r e g e n e r a t i o n on randomly s e l e c - t e d s u r f a c e s o f t h e b u r n .

A r t i f i c i a l seeding . - -The p r imary s i t e f o r t h e a r t i f i c i a l s e e d i n g s t u d y was abou t 3 km from t h e Wickersham Dome r i d g e t o p s t u d y a r e a ( s t a n d s BS-3C and BS-3H). A n o r t h and s o u t h s l o p e (same d r a i n a g e ) were s e l e c t e d f o r p l o t e s t a b l i s h m e n t ; 10 p l o t s were seeded on each a s p e c t . Each p l o t c o n s i s t e d o f f i v e r e c t a n g u l a r s u b p l o t s ( 5 - by 30-cm). The two s i d e s u b p l o t s and t h e middle s u b p l o t were seeded w i t h 1 ,000 s e e d s o f e i t h e r b l a c k s p r u c e , w h i t e s p r u c e , o r p a p e r b i r c h . The b l a c k s p r u c e s e e d were c o l l e c t e d from t r e e s i n t h e burned a r e a and had an ave rage g e r m i n a t i o n of 41 p e r c e n t .

BS-1H

1 9 ~ h i s s ec t ion was prepared by S. F. Claut ice , Fo res t e r , Alaska Division

BS-3H

of Fores t , Lands, and w a t e r - ~ a n a ~ e m e n t , Fairbanks; J . C . Zasada, S i l v i c u l t u r i s t , USDA Forest Serv ice , P a c i f i c Northwest Fores t and Range Experiment S t a t i o n , I n s t i t u t e of Northern Fores t ry , Fairbanks, Alaska; and B. J . Neiland, Professor , School of Agr icul ture and Land Resources Management, Univers i ty of Alaska, Fairbanks.

The b i r c h and whi te sp ruce seeds were c o l l e c t e d i n t h e Bonanza Creek Experimental F o r e s t a t an e l e v a t i o n of about 200 m . Labora- t o r y germinat ion was 68 and 2 7 p e r c e n t f o r whi te sp ruce and b i r c h , r e s p e c t i v e l y . P l o t s were seeded i n e a r l y June 1972 on minera l s o i l , a s h , and c h a r r e d s u r f a c e s .

The second p a r t of t h e a r t i f i c i a l seed ing s t u d y was conducted on a f i r e l i n e a d j a c e n t t o t h e r i d g e t o p s t u d y s i t e a t Wickersham Dome. A l l o r g a n i c m a t t e r had been removed, l e a v i n g a b a r e minera l s o i l s u r f a c e . White s p r u c e , b l a c k s p r u c e , and b i r c h were seeded i n October 1971. Birch p l o t s were seeded w i t h 300 seeds (germina- t i o n 65 p e r c e n t ) , whi te and b l a c k sp ruce wi th 2 0 0 seeds (germina- t i o n 75 and 65 p e r c e n t , r e s p e c t i v e l y ) . Observat ions were made weekly u n t i l t h e f i r s t s e e d l i n g was observed on June 2 1 , 1972; s e e d l i n g coun t s were r e p e a t e d on J u l y 2 1 and August 2 0 .

The experiment c o n s i s t e d of t h r e e s t u d y b l o c k s . Within each b lock , each s p e c i e s was r e p l i c a t e d t h r e e t imes . Each r e p l i c a t i o n c o n s i s t e d of a 1-m2 p l o t ; w i t h i n t h i s p l o t two 25-cm-diameter c i r c u l a r p l o t s were l o c a t e d . One of t h e s e p l o t s was covered w i t h hardware c l o t h ; t h e o t h e r was u n p r o t e c t e d .

Germination of b i r c h e x h i b i t e d a s i m i l a r p a t t e r n on bo th a s p e c t s ; i . e . , a peak i n mid-June t o l a t e June wi th r e l a t i v e l y l i t t l e a d d i - t i o n a l germinat ion. Both whi te and b l a c k sp ruce e x h i b i t e d a s i m i l a r response on t h e n o r t h s l o p e ; however, peak a c t i v i t y was l a t e r than t h a t observed fo rb i rch . On t h e s o u t h s l o p e , sp ruce germinat ion d i d n o t e x h i b i t a d i s t i n c t peak ( f i g . 1 8 ) . These d i f f e r e n c e s i n response of s p e c i e s t o a s p e c t a r e b e l i e v e d r e l a t e d t o h o t , d r y s u r f a c e c o n d i t i o n s which occur red on t h e s o u t h s l o p e i n l a t e June ( C l a u t i c e 1974) .

k t t h e f i r e l i n e s i t e , no germinat ion was observed b e f o r e June 1 4 on e i t h e r t h e p r o t e c t e d o r unpro tec ted p l o t s . During t h e week p r i o r t o June 2 1 , approximate ly 80 p e r c e n t of t h e annual germinat ion occur red i n t h e p r o t e c t e d p l o t s . In t h e unpro tec ted p l o t s fewer germinants were observed; however, a h i g h e r pe rcen tage (90) were from t h e p e r i o d p r i o r t o June 2 1 ( t a b l e 22) . The r e l a - t i v e l y low number of s e e d l i n g s produced i n d i c a t e t h a t l o s s of seed on unpro tec ted p l o t s was s i g n i f i c a n t . S u r v i v a l of germinants through e a r l y September was s i m i l a r on n o r t h and s o u t h s l o p e s . S u r v i v a l of b i r c h was l o w e s t , fo l lowed by whi te sp ruce and b l a c k sp ruce . Percentage of s u r v i v a l , however, depended on t h e germina- t i o n d a t e . June germinants e x h i b i t e d poor s u r v i v a l on t h e s o u t h s l o p e ; s u r v i v a l of J u l y and August germinants was g e n e r a l l y h i g h e r . On t h e n o r t h s l o p e , f i r s t growing season s u r v i v a l was h i g h e s t f o r June and August germinants ( f i g . 1 9 ) . On t h e f i r e l i n e s i t e s , s e e d l i n g s germinat ing p r i o r t o June 2 1 c o n t r i b u t e d t h e m a j o r i t y of t h e s e e d l i n g s t o t h e August 2 1 p o p u l a t i o n ( t a b l e 22) .

Mois ture and temperature a r e two impor tant f a c t o r s r e g u l a t i n g seed ge rmina t ion . Average d a i l y maximum and minimum minera l s o i l s u r f a c e t empera tu res dur ing peak b i r c h germinat ion on t h e sou th s l o p e were 7 0 C and 240C; on t h e n o r t h s l o p e , 4 0 C and 1 7 O C . During t h e h o t t e s t p e r i o d of t h e summer (June 2 7 t o J u l y l l ) , when m o r t a l i t y reached a maximum on t h e s o u t h s l o p e , average d a i l y maximum s u r f a c e temperatures were 290C on minera l s o i l , 3g°C on

SOUTH SLOPE

9 I I ? ~ e - 4 BIRCH I I \ 1 L -- 4 BLACK SPRUCE

I - WHITE SPRUCE

SUR 100

I

U 0

VIVAL (percent)

SOUTH SLOPE

I

- WHITE SPRUCE -----4 BLACK SPRUCE

NORTH SLOPE

Figure 18.--Weekly g e r m i n a t i o n o f F i g u r e 19.--Percent o f birch, w h i t e seeded birch, b l a c k s p r u c e , and s p r u c e , and b l a c k s p r u c e s e e d l i n g s w h i t e s p r u c e on north and s o u t h s u r v i v i n g t o September b y d a t e o f s l o p e s 1 year a f t e r f i r e ( 1 9 7 2 ) . g e r m i n a t i o n ( 1 9 7 2 ) -

Table 22--Germination and survival of birch and white arid black spruce seedlings on mineral soil on 3 dates during the 2d growing season after a wildfire, Wickersham Dome study area

Birch : 1 0 3.5 0 / 1.0 0.7 0 0.7/ 1.0 2 5.0 4.0 2.7/ 2.3 .7 0 3.4/ 2.3 3 3.7 1.0 3.7/ .3 .3 .3 4.0/ .6

White spruce : 1 25.3 3.0 24.3 1.7 17.3 .7 41.6/ 2.4 2 28.7 .3 23.7/ .3 7.7 0 31.4/ .3 3 35.3 25.0 22.3/22.3 2.0 0 24.3/22.7

Black spruce : 1 3.7 0 3.0/ 0 .7 0 3.7/ 0 2 2.0 0 1.3/ 0 1.7 0 3.0/ .3 3 11.0 2.0 8.0/ 1.3 1.0 0 g.O/ 1.3

L/~eeded area protected by hardware cloth.

2/~rotected/unprotected seedlings.

Species and

number

July 21 June 21

Surviving June 21

seedling&/

August 21

Pro- tected'

June 21 seedling

Unpro- tected

New seedlings July 21 seedling&/ Pro-

tected Unpro- tected

~otalg~ New seedlings

Pro- tected

",,- tected

a s h , and 41°c on c h a r r e d moss. Abso lu te maximum t e m p e r a t u r e s r e c o r d e d d u r i n g t h i s p e r i o d were 41oC, 6 8 O ~ , and 7 7 ' ~ on m i n e r a l s o i l , a s h , and c h a r r e d moss, r e s p e c t i v e l y . S o i l m o i s t u r e was n o t measured; however, m i n e r a l s o i l had a c o n s i s t e n t l y m o i s t s u r f a c e on t h e n o r t h s l o p e .

NaturaZ r e v e g e t a t i o n . - - S i g n i f i c a n t d i f f e r e n c e s e x i s t e d between s u r f a c e c o n d i t i o n , s p e c i e s compos i t ion , and major t y p e o f r e p r o - d u c t i o n between t h e n o r t h and s o u t h s l o p e s ( t a b l e s 23 and 24) . A c h i - s q u a r e t e s t o f t h e d i f f e r e n c e s i n t h e d e n s i t y v a l u e s of t h e June s p e c i e s among t h e s u r f a c e s showed t h e s u r f a c e c l a s s i f i c a t i o n t o be s i g n i f i c a n t a t t h e 0.05 l e v e l . S u r f a c e s w i t h t h e l a r g e s t amount o f s i m i l a r v e g e t a t i o n were " f l a t c h a r r e d moss" and t h e more d e e p l y burned "convolu ted burned moss." Both t h e s e c o n d i - t i o n s were i n c l u d e d i n t h e g e n e r a l modera t e ly burned c a t e g o r y .

Effects of Fire on Arthropod Distribution2'

The sampl ing o f a r t h r o p o d p o p u l a t i o n s i n 1972 and 1973 was l i m i t e d t o 1 0 p i t t r a p s i n t h e burned and t h e unburned c o n t r o l a r e a s . The p i t t r a p s were checked weekly f o r 9 weeks, and t h e t r a p p e d a r t h r o p o d s were c o l l e c t e d and s t o r e d i n 80 p e r c e n t e t h a n o l . The specimens were s e p a r a t e d and t h e d a t a ana lyzed a c c o r d i n g t o f i v e major c a t e g o r i e s : s p i d e r s , Col lembola , m i t e s , C o l e o p t e r a , and o t h e r a r t h r o p o d s .

The t o t a l number o f a r t h r o p o d s c o l l e c t e d i n 1973 was s i g n i f i - c a n t l y lower t h a n s i m i l a r c o l l e c t i o n s from 1972 ( t a b l e 25) . The unburned c o n t r o l and burned a r e a s produced 44 and 23 p e r c e n t fewer a r t h r o p o d s , r e s p e c t i v e l y , i n 1973. I n b o t h y e a r s , however, t h e burned a r e a s produced more specimens t h a n t h e unburned con- t r o l a r e a s , which i n d i c a t e s e i t h e r a h i g h e r p o p u l a t i o n o f a r t h r o - pods o r h i g h e r a r t h r o p o d a c t i v i t y i n t h e burned a r e a s and t h e r e - f o r e a g r e a t e r chance o f c a p t u r e .

There was a s i g n i f i c a n t d e c r e a s e i n t h e p e r c e n t a g e of m i t e s ( 4 6 ) , Collembola ( 4 3 ) , and C o l e o p t e r a (72) c a p t u r e d i n 1973 and no s i g n i f i c a n t change i n t h e " o t h e r a r t h r o p o d s " c a t e g o r y . The number o f s p i d e r s c a p t u r e d i n burned a r e a s i n 1973 was 1 . 3 t imes h i g h e r t h a n i n 1972, and i n 1973 s p i d e r numbers were 3.0 t imes h i g h e r i n t h e burned a r e a t h a n i n t h e unburned c o n t r o l . The d e - c r e a s e i n most a r t h r o p o d p o p u l a t i o n s i n burned a r e a s compared w i t h t h e i n c r e a s e i n s p i d e r p o p u l a t i o n s can be a t t r i b u t e d t o p r e d a t i o n by s p i d e r s . S p i d e r p r e d a t i o n would be h i g h e r i n t h e burned a r e a because o f s p a r s e ground v e g e t a t i o n which o f f e r s p r o t e c t i o n t o p r e y s p e c i e s .

20~his section was prepared by R. C. Beckwith, Principal Insect Ecologist, Forestry Sciences Laboratory, Corvallis, Oregon, and R. A . Werner, Research Entomologist, Institute of Northern Forestry, Fairbanks, Alaska; both men are with USDA Forest Service, Pacific Northwest Forest and Range Experiment Station.

Table 23--Density o f vege ta t ion on 4 burned s u r f a c e s on t h e sou th s l o p e dur ing t h e 2d growing season a f t e r t h e Wickersham Dome f i r e

Alnus crispa

Betula papyrifera

Calamagrostis canadensis

Corydalis sempervirens

Epi lobi um angusti folium

Rosa acicularis

Rubus idaeus

v June Sept .

v June Sept .

s June Sept .

s June Sept .

s June Sept .

v June Sept .

s June Sept .

Spec ies

- -Stems pe r sauare&e&i- - - - - - 0.05 0 0 0 .31

.99 0 0 .89 0 7.58 0 .61 0 7.95 0 .64 7.70 0 0 6.37

17.96 .38 0 14.45 -42 9 .85 5.27 1.88

1.04 12.88 6.09 2.79 .21 0 .61 -24 .47 0 .81 .42 .10 0 0 .06 .42 0 0 .24 .05 0 3 .65 .58 .10 0 3.04 .58

To ta l area

Percent

6 1 2 3 3

41 44 32 4 7 1 5 18 3 9

21 32

Origin o f repro-

ductio&/ Density

i / v = vege ta t ion ; s r seed.

/only upper s u r f a c e o f mosz cha r red .

g 1 ~ e e p e r c h a r r i n g i n moss l a y e r (moderately burned ) . "var iable burning i n moss l a y e r (modeyately burned) .

?/MOSS l a y e r consumed, on ly a sh remaining on s u r f a c e o f mineral s o i l (heav i ly burned)

Frequency

Table 24--Density o f vegeta t ion on 7 burned s u r f a c e s on t h e nor th slope during t h e 2d growing season after t h e Wickersham Lkme f i r e

Month

- - - - - - - - - - - - -Stem per square meter- - - - - - - - - - - - - calamagrostls v June 0 4.12 3.04 4.85 6.36 1.23 0 3.00 canadensi s Sept . 0 6.18 4.15 8.44 7.63 1.23 0 4.31 Epi 1 obi um s June 0 0 0 0 0 0 0 0 angustifolium Sept. 0 0 .18 0 0 0 0 .03 Equlsetum v June 17.11 13.9219.83 22.89 23.41 37.42 18.64 21.74 pratense Sept . 18.42 18.04 23.34 28.28 25.45 43.56 28.81 25.97

Led um v June 38.16 15.46 2.49 0 0 0 0 2.77 groenlandicum Sept . 38.16 23.71 4.70

S -09 0 .51 0 L.16

Marchan tla June 0 0 0 0 0 9/:.80 91.12 polymorpha Sept. 0 0 0 0 0 0 z116.90 9l.32

OX~COCCUS v June 81.58 0 0 0 0 0 0 2.00 mlcrocarpus Sept . 78.95 10.82 0 0 0 0 0 2.61 Picea s June 1.32 0 0 0 0 0 0 .03 marlana Sept . 1.32 0 0 0 0 0 0 .03

Pol ygonum v June 0 0 .18 0 0 0 0 .06 alaskanum Sept. 0 0 .18 0 0 0 0 .06

Polytrlchum sp . s June 0 0 0 0 0 0 0 0 Sept. 0 0 0 .36 .25 3.68 0 .35

Rosa v June 0 0 0 0 0 0 0 0 aclcularis Sept. 0 0 0 .36 0 0 0 .13

~ u b u s v June 3.95 2.06 5.81 .63 .25 0 0 3.52 chamaernorus Sept. 3.95 5.15 8.12 1.89 .25 0 0 3.97

~ u b u s s June 0 0 0 0 0 .61 0 .03 idaeus Sept. 0 0 0 0 0 .61 3.39 . l o

Spiraea v June 0 0 .28 0 0 0 f:

.10 beauverd~ ana Sept . 0 0 .37 0 0 0 .13 Vaccini um v June 0 1.03 .18 0 0 0 0 .13 uliginosum Sept . 0 1.03 .18 0 0 0 0 .13

Vacclnium v June 0 161.34 10.70 .18 0 0 0 3.90 vitis-idaea Sept . 0 162.89 10.88 -18 0 0 0 4.06

l'v = vep;etation; s = $eed.

2 '~nburned.

'MOSS scorched and killed by h e a t .

k/Only upper s u r f a c e o f moss charred.

Z ' k p e r charrlnp i n moss l a y e r (moderately burned).

k'variariable burning in msr layer (moderately b a d ) . y 0 n l y ash remaining on s u r f a c e o f mineral s o i l s (heavily burned).

B / ~ i n e r a l s o i l exposed by f i r e l ine cons t ruc t ion .

S 4 y ~ x p r e s s e d in percent cover.

Density

Species

Percent

38 47 0 3

97

L igh t ly burned mossZ/

Origin of repro-

d u c t i d /

Convoluted burn~cJ m o s s

F l a t charred moss?/

AS&/

Month

Density Total a rea

Density Frequency

' lable 25--Numbers of arthropods co l lec ted from p i t t r aps , Wickersham Dome, 1 and 2 1 / years a f t e r a 1971 wi ld f i r e -

1972 : Unburned cont ro l 320 178 1,142 53 454 2,147 Heavy burn 557 701 866 113 382 2,619

1973 : Unburned cont ro l 249 167 500 9 270 1,195 Heavy burn 736 381 494 32 286 2,029

Total Year and area

2'3ased on 9 s imi l a r co l l ec t i cn da t e s f o r each year.

Numeric Response of Microtine Rodents After Fire2'

Spiders

P o s t f i r e p o p u l a t i o n r e s p o n s e o f t h e n o r t h e r n r ed -backed v o l e (CZethrionomys r u t i l u s ) and t h e t u n d r a v o l e ( ~ i c r o t u s oeconomus) was i n v e s t i g a t e d d u r i n g a y e a r l o n g l i v e t r a p p i n g from June 2 , 1972, t h rough June 1 8 , 1973, i n t h e s e v e r e l y burned a r e a and a d j a c e n t unburned c o n t r o l a r e a of b l a c k s p r u c e t a i g a a t t h e Wickersham r i d g e t o p s i t e ( p l o t s BS-3H and BS-3C).

These a r e a s were t r a p p e d a g a i n i n t h e f a l l o f 1973 and t h e subsequen t summers o f 1974, 1975, and 1976. The d e n s i t y i n f o r - mat ion summarized h e r e p e r t a i n s t o t h e 1972-73 y e a r and t h e summer o f 1974. O the r a s p e c t s o f t h i s work have been p r e s e n t e d by West (1977) and a more e x h a u s t i v e t r e a t m e n t i n a Ph.D. t h e s i s (West 1979) .

A l l p o p u l a t i o n measurements were t a k e n on two p a r a l l e l l i v e - t r a p p i n g g r i d s , one i n t h e burned a r e a and one i n t h e unburned c o n t r o l a r e a . Both g r i d s c o n s i s t e d o f 96 l a r g e f o l d i n g aluminum l i v e t r a p s , spaced a t 10-m i n t e r v a l s i n an 80- by 120-m c o n f i g u r a - t i o n a l o n g t h e r i d g e t o p . With a 5-m boundary s t r i p assumed, t h i s s p a c i n g produced a t r a p p i n g a r e a o f 0 .96 h a . The t r a p s were b a i t e d w i t h r o l l e d o a t s and o p e r a t e d d u r i n g t h e n i g h t hour s ( abou t 10 p.m. t o 8 a.m.) f o r 3 c o n s e c u t i v e days e v e r y 2 weeks. B a s i c i n f o r m a t i o n c o l l e c t e d a t each c a p t u r e i n c l u d e d w e i g h t , s e x , p o i n t of c a p t u r e , and r e p r o d u c t i v e c o n d i t i o n . Toes o f v o l e s were c l i p p e d f o r i n d i v i d u a l r e c o g n i t i o n .

arthropods Other Mites

The o v e r a l l t r e n d s i n s i z e o f p o p u l a t i o n s f o r n o r t h e r n r e d - backed v o l e and t u n d r a v o l e f o r 1972-74 a r e shown i n f i g u r e 20. The most s t r i k i n g f e a t u r e o f t h e p o p u l a t i o n d e n s i t y o f n o r t h e r n r ed -backed v o l e i s i t s pronounced annua l c y c l e . Breeding s e a s o n s

21~his section was prepared by S. D. West, graduate student, Museum of Vertebrate Zoology, University of California, Berkeley.

Collembola Coleoptera

- CLETHRIONOMYS RUTILUS IN AN UNBURNED CONTROL AREA ---- C. RUTILUS IN A BURNED AREA

-......-- MICROTUS OECONOMUS IN A BURNED AREA

t

Figure 20.--Population t r e n d s f o r the nor thern red-backed v o l e and t h e tundra v o l e i n an area burned i n 1971 and an ad jacen t unburned con t ro l area .

a r e p e r i o d s of c o n s i s t e n t i n c r e a s e , c h a r a c t e r i s t i c o f p o p u l a t i o n s w i t h o v e r l a p p i n g g e n e r a t i o n s . These peak d e n s i t i e s a r e i n t e r - med ia t e i n te rms o f t h e peak d e n s i t i e s observed f o r n o r t h e r n r ed -backed v o l e i n i n t e r i o r Alaska w h i t e s p r u c e f o r e s t s ( P r u i t t 1957) . The b r e e d i n g seasons f o r n o r t h e r n r ed -backed v o l e s ex tended from May t o September; most a c t i v i t y was c o n c e n t r a t e d i n June, J u l y , and August . The a d u l t s e x r a t i o i n t h e p o p u l a t i o n was approx ima te ly one t o one.

I n t h e unburned c o n t r o l a r e a , t h e s p r i n g and f a l l d e n s i t y i n b o t h 1972 and 1973 were s i m i l a r . The f a l l 1973 t r a p p i n g p e r i o d p r o b a b l y caught a l l b u t two o r t h r e e v o l e s t h a t were on t h e g r i d a t t h a t t ime . The s l i g h t l y l a r g e r s p r i n g 1974 p o p u l a t i o n might i n d i c a t e improved w i n t e r s u r v i v a l compared w i t h s u r v i v a l i n 1973, o r t h a t t h e s p r i n g 1974 immigra t ion r a t e was h i g h e r t h a n 1973, r e s u l t i n g i n a l a r g e r p o p u l a t i o n i n June 1974. A h i g h r e c a p t u r e r a t e d u r i n g t h e f a l l 1973 t r a p p i n g p e r i o d s and t h e concomitant absence o f r e p r o d u c t i v e l y a c t i v e v o l e s s u g g e s t t h a t most v o l e s on t h e s t u d y a r e a had been marked by t h e 1st week i n Oc tobe r . Only 1 v o l e o u t o f 2 2 marked i n t h e f a l l o f 1973 was c a p t u r e d t h e n e x t s p r i n g , however, which i n d i c a t e s an i n f l u x of unmarked a d u l t s . Th i s p a t t e r n was a l s o s e e n i n s p r i n g 1973 b u t t o a l e s s e r e x t e n t (West 1974) .

On a s e a s o n a l b a s i s , m o r t a l i t y f o r n o r t h e r n r ed -backed v o l e was h i g h e s t i n t h e f a l l , l owes t i n w i n t e r , and i n t e r m e d i a t e i n summer. S p r i n g r a t e s were d i f f i c u l t t o de t e rmine because o f s m a l l s i z e of p o p u l a t i o n .

The s u b s t a n t i a l i n c r e a s e i n d e n s i t y i n f a l l 1974 was n o t due t o an extended b r e e d i n g s e a s o n r e l a t i v e t o t h e p r e c e d i n g 2 y e a r s - The absence o f p r e g n a n t , l a c t a t i n g , o r e s t r o u s females and t h e absence o f s c r o t a 1 males ind ica t ed t h a t r e p r o d u c t i o n had ceased i n b o t h y e a r s by t h e end o f September. I n f a c t , t h e number o f r e p r o - d u c t i v e l y a c t i v e females was s i m i l a r from J u l y th rough September each y e a r . The d i f f e r e n c e i n d e n s i t y was most l i k e l y due t o i n c r e a s e d s u r v i v a l o f j u v e n i l e s i n l a t e August and September. The d e n s i t y i n 1975 was n e a r l y i d e n t i c a l t o t h a t o f 1974, and t h e d e n s i t y i n 1976 was abou t t h e same a s 1972 and 1973. Minimum annua l d e n s i t i e s have a l l been fewer t h a n 10 v o l e s , l e n d i n g f o r c e

to the arguments of Whitney (1976) that the northern red-backed vole is not cycling in the classic microtine fashion in interior Alaska. The annual cycle of maximum density appears to be determined by the survival of juveniles from the fall generation.

In 1972, activity of red-backed voles in the heavily burned area was very low over the first postfire growing season and was confined to the late summer-early winter period from late July to early November. Only seven voles were caught in the burned area during that time; 2 of these accounted for 12 of the 18 total captures in the burned area, and these 2 were caught in the unburned control area as well. The fall 1973 trapping indicated essentially the same density as that of the previous fall. None of the three voles known to be alive in fall 1973 was recaptured; the spring 1974 population consisted of immigrants. In 1973 the red-backed voles abandoned the burned area as they had the pre- ceding winter. No red-backed voles were caught in the burn until the latter part of July 1974, when the population in the burned area increased substantially. Both postpartum females and very young voles were caught, which indicated breeding on the burned area. Voles overwintered in the burned area for the first time in 1974.

The tundra vole (~icrotus oeconomus) was captured only one time (August 1972) in the unburned control area and was not captured in the burned area until the spring of 1974. Observa- tions in the burned area immediately after snowmelt in 1974 indicated that tundra voles were present prior to the thaw. Several runways and burrows were found, primarily in moist, low- lying zones and in root tangles. These animals could have been either overwintering animals not caught in fall 1973 or, more likely, immigrants during early spring 1974. As shown in figure 20, the tundra vole population increased until mid-August and declined thereafter. The possibility exists that the decline was due to the increasing population of red-backed voles present on the burned area. As plant succession proceeds on the burned area, the vegetational composition will more closely resemble the habitat requirements of the tundra vole, and a resident population should become established. Trapping in several successional areas where time since last fire is known indicates that peak tundra vole densities at Wickersham Dome can be expected in 4-12 years from 1974, depending on the rate of plant succession.

Habitat Utilization By Snowshoe Hares In Burned

and Unburned Black Spruce Communitied2

The impact of snowshoe hares on secondary succession after fire has not been determined in the taiga of interior Alaska.

L L This sec t ion was prepared by J . 0 . Wolff, Research Associate, Museum

of Vertebrate Zoology, Universi ty of Ca l i fo rn ia , Berkeley, and I n s t i t u t e of Northern Forestry,Fairbanks, Alaska; C . T . Cushwa, Wild l i fe Biologis t , Forest Environment Research, USDA Forest Service, Washington, D . C . ; and K . P. Burnham, Biometrician, Western Energy and Land Use Team, U.S. Fish and Wildlife Service, For t Col l ins , Colorado.

The 1971 fire at Wickersham Dome and the adjacent, unburned 70-year-old black spruce stand presented an opportunity to study habitat utilization by snowshoe hares in the two communities. The major objectives of this portion of the study were to compare population densities of snowshoe hares in the burned and unburned control stands and to relate these to availability of food and cover. Food habits and browse intensities by snowshoe hares were also recorded to determine the impact of snowshoe hares on forest regeneration and plant succession. Wolff (1977) reported on the snowshoe hare project at the Wickersham Dome study area.

In summer 1972, two 40-ha grids of live-traps were established, one in the burned area and one in the adjacent, unburned control area. Each grid consisted of 100 traps in a 10 by 10 array with 60 m between any two traps. In 1974, each grid was reduced to an 8 by 10 array of traps encompassing an effective area of 34 ha. Single-door traps of wire were made according to the method described by Cushwa and Burnham (1974) and were baited with alfalfa cubes. Trapping periods varied from 6 to 10 consecutive days and were initiated in November 1972. Spring trapping was conducted in Apri.1 when the hares were still on a winter diet. The ears of captured hares were tagged, and the hares were weighed and sexed prior to release. Individual traps were numbered to identify exact locations of captures for movement calculations. Vegetation was sampled in both areas to determine densities of trees and shrubs and percent ground cover of low shrubs, herbs, mosses, and lichens.

In the Wickersham Dome fire, hares consumed virtually all the postfire willow sprouts during September following the July burn (fig. 21). During the winter of 1971-72, they consumed charred bark of black spruce, aspen, and birch (fig. 22). The second winter after the fire (1972-73), hares consumed all the aspen sucker regrowth in several stands (fig. 23). From 1971 to 1973, 100 percent of the available hardwood browse (willow, alder, and aspen) was consumed in the unburned control and a 200-m strip of the burned area paralleling the unburned area (table 26). From 1973 to 1976, browse intensity by snowshoe hares decreased con- currently with an overall decline in the hare population.

The high intensities of browsing on willow and aspen for 2 years after the fire stimulated lateral branching which increased vegetative growth. Current annual growth was removed each winter, but the long-term effects were increased production of aboveground biomass (Wolff 1978a).

The results from live-trapping at Wickersham Dome from 1972 to 1976 are shown in table 27 and illustrated in figure 24. We used the Schnabel and Lincoln indices with a 95-percent confidence interval to estimate populations (Giles 1969).

In the fall of 1972, 74 hares were live trapped, tagged, and released in the unburned control; only 3 hares were caught in the burned area. A population estimate for the unburned control for 1971 would be about 200 animals (Ernest 1974). By April 1973 the population of hares in the burned area had increased to 15, 13 of

Figure 21 .--Hares consumed v i r t u a l l y a l l the w i l l o w s p r o u t regrowth dur ing September a f t e r the J u l y w i l d f i r e ,

Figure 22.--Evidence of browsing b y snowshoe h a r e s o n charred b l a c k spruce a t the 1971 Wickersham Dome f i r e site.

Figure 23.--Consumption o f aspen regrowth b y hares the second winter a f t e r the 1971 Wickersham Dome f i re .

Table 26--Intensity of browsing by snowshoe hares at the Wickersham 1 / Dome study site for 5 years after a 1971 wildfire-

Burned 100 100 3 k 1 . 7 0 0 Unburned control 100 100 45 + 3.3 4 + 2.3 1 + 1.2

Area

L'plus or minus signs indicate standard error of the mean.

1972-73 1973-74 1974-75 1975-76

Table 27--Population estimates of snowshoe hares for the Wickersham Dome unburned control, based on

data of recaptured, marked hare&

95-percent confi- - - - - -Number- - - - - Average dence interval

NOV. 1972 164 90 74 85 69-105 Apr. 1973 221 152 67 69

42 57-79

Apr. 1974 117 74 43 33-52 July 1974 44 21 22 27 16-41 Sept. 1974 19 9 10 12 5-23 NOV. 1974 12 2 11 26 4-147 Apr. 1975 5 1 4 8 1-156 Rug. 1975 12 8 4 4 2-9 NOV. 1975 4 2 4 5 0-14 Apr. 1976 17 10 9 8 4-20 Au~. 1976 54 29 21 20 14-27

L/~opulation estimates are number of hares per 34 hectares.

2'~iles f 1969 ) .

Trapping period

Average

78 70 45 29 10 24 6 4 5 7 23

95-percent confidence interval

52-112 46-102 29-65 6-108 1-95 2-468 0-117 1-15 0-39 3-16 17-29

Total captured

80 -

Figure 24.--Number o f marked snowshoe h a r e s caught i n the burned area and t h e unburned c o n t r o l a t Wickersham

a Dome a f t e r a 1971 w i l d f i r e , 1972-76.

TRAPPING PERIOD

Total recaptured

which were marked t r a n s i e n t s from t h e unburned c o n t r o l ; t h e number of an ima l s caugh t i n t h e c o n t r o l was 69 , 31 o f which were r e c a p - t u r e d from t h e f a l l p o p u l a t i o n . F i e l d o b s e r v a t i o n s r e v e a l e d t h a t hardwood browse had become l i m i t e d i n t h e unburned c o n t r o l , and h a r e s were f o r c e d t o l e a v e t h e p r o t e c t i o n o f t h e mature f o r e s t and e n t e r t h e open burn i n s e a r c h o f food. S u r v i v a l r a t e s of marked an ima l s were much g r e a t e r i n t h e dense b l a c k s p r u c e s t a n d t h a n i n t h e burned a r e a o r t h e more open p o r t i o n s o f t h e s p r u c e s t a n d .

One y e a r l a t e r , i n t h e s p r i n g o f 1974, o n l y 4 3 h a r e s were t agged i n a 7-day t r a p p i n g p e r i o d i n t h e unburned c o n t r o l and 1 i n t h e burned a r e a . Hares had been s e e n c r o s s i n g from t h e c o n t r o l i n t o t h e burned a r e a , b u t t h e r e appeared t o be no permanent r e s i d e n t s i n t h e burned a r e a . Q u a n t i t a t i v e measurements r e v e a l e d t h a t t h e r e was enough hardwood browse i n t h e unburned c o n t r o l t o m a i n t a i n a p o p u l a t i o n a t t h a t l e v e l . Browse i n t e n s i t y i n t h e burned a r e a was o n l y 3 p e r c e n t , whereas i n t h e unburned c o n t r o l abou t 45 p e r -

:::id Population estimate

~chnabely inc cold'

c e n t of t h e a v a i l a b l e browse was consumed. By J u l y 1974, o n l y 2 2 h a r e s were caugh t i n t h e unburned c o n t r o l ; by November, o n l y 11. No h a r e s were caugh t i n t h e burned a r e a from 1974 t o 1976. The low number o f h a r e s marked i n November 1975 was though t t o be an u n d e r e s t i m a t e caused by a change i n t r a p p i n g p r o c e d u r e s . The p o p u l a t i o n r eached a low o f 4 h a r e s i n A p r i l 1975 b u t i n c r e a s e d t o 2 1 by August 1976.

The p o p u l a t i o n d e c r e a s e d from a h i g h o f s i x h a r e s / h a i n t h e f a l l o f 1971 t o a low o f 0.12 h a r e / h a i n A p r i l 1975. The d e c l i n e was g r a d u a l b u t c o n t i n u o u s th rough t h e summer r e p r o d u c t i v e s e a s o n s a s w e l l a s d u r i n g t h e w i n t e r . The d e c l i n e may have been i n i t i a t e d by d e c r e a s e d q u a n t i t y and q u a l i t y o f f o r a g e d u r i n g t h e peak popu la - t i o n d e n s i t i e s from 1971 t o 1973, which r e s u l t e d i n reduced p h y s i o - l o g i c a l f i t n e s s and e v e n t u a l s t a r v a t i o n . The c o n t i n u e d d e c l i n e from 1 9 7 3 t o 1975 was p r o b a b l y due t o i n c r e a s e d r a t e s o f p r e d a t i o n which i n c r e a s e d h a r e m o r t a l i t y (Wolff 1977) .

Food h a b i t s of snowshoe h a r e s were de te rmined by m i c r o s c o p i c a n a l y s i s o f stomach c o n t e n t s (Wolff 1978b) . B l u e b e r r y , lowbush c r a n b e r r y , f i r e w e e d , and h o r s e t a i l made up 47 p e r c e n t o f t h e s p r i n g d i e t ; and l e a v e s o f b i r c h , w i l l o w , r o s e , and o t h e r dec iduous s h r u b s made up 76 p e r c e n t o f t h e summer d i e t ( f i g . 2 5 ) . Trap r e s u l t s i n d i c a t e t h a t h a r e s m i g r a t e s e a s o n a l l y i n r e s p o n s e t o t h i s change i n d i e t . I n t h e summer, h a r e s p r e f e r open a r e a s where b l u e b e r r y , lowbush c r a n b e r r y , and o t h e r he rbaceous p l a n t s a r e more p l e n t i f u l . During t h e w i n t e r when t h e h e r b s and low s h r u b s a r e cove red w i t h snow, h a r e s move back i n t o t h e dense b l a c k s p r u c e t h i c k e t s where t h e y f e e d on s p r u c e n e e d l e s and ba rk and t w i g s o f b i r c h , w i l low, and a l d e r .

P o p u l a t i o n s o f snowshoe h a r e s i n Alaska and th roughou t t h e b o r e a l f o r e s t s o f North America appea r t o f l u c t u a t e on a 1 0 - y e a r c y c l e . D e n s i t i e s may show a 6 0 - f o l d d i f f e r e n c e from h i g h t o low y e a r s and r ange from 800 t o 1 2 hares /km2. The s t u d y o f snowshoe

WINTER APRIL MAY SUMMER FALL

Figure 25.--Diet of snowshoe hares at different times of the year.

HERBS 0 SPRUCE NEEDLES

DECIDUOUS LEAVES WOODY BROWSE

h a r e s a t Wickersham Dome was conducted d u r i n g t h e peak and d e c l i n - i n g phases o f t h e c y c l e . When t h e p o p u l a t i o n d e n s i t i e s were low, h a r e s remained i n dense b l a c k s p r u c e o r w i l l o w - a l d e r t h i c k e t s where food and cove r were p l e n t i f u l . During h i g h d e n s i t i e s when h a r e s exceeded t h e i r o v e r w i n t e r food s u p p l y i n p r e f e r r e d h a b i t a t (1971 th rough 1 9 7 3 ) , t h e y invaded more open and r e c e n t l y burned a r e a s t o f o r a g e on new growth o f woody browse p l a n t s . During t h e s e h i g h d e n s i t i e s , h a r e s occup ied a l l s u i t a b l e h a b i t a t , and browse i n t e n s i t y r eached 100 p e r c e n t . Excess ive browsing by h a r e s had a n a d v e r s e e f f e c t on r e g e n e r a t i o n o f woody p l a n t s from 1971 through 1973. Long-term e f f e c t s o f e x c e s s i v e browsing may, however, r e s u l t i n i n c r e a s e d p r o d u c t i o n o f woody browse because o f l a t e r a l b ranch ing of browsed s t ems . I n c o n c l u s i o n , we f e e l t h a t h a r e s have t h e g r e a t e s t impact on r e g e n e r a t i o n o f t r e e s and woody s h r u b s f o r o n l y a 2 - t o 3 - y e a r p e r i o d i n a 1 0 - y e a r c y c l e .

The Wickersham Dome f i r e o c c u r r e d i n l a t e June 1971 and burned o v e r approx ima te ly 6 300 h a . The f i r e , which was t y p i c a l of i n - t e r i o r Alaska w i l d f i r e s , was b rough t under c o n t r o l a f t e r t r a c t o r c o n s t r u c t i o n o f 113 km o f f i r e l i n e s and a e r i a l a p p l i c a t i o n of some 242 000 l i t e r s o f f i r e r e t a r d a n t . Be fo re t h e f i r e , t h e a r e a was mos t ly cove red w i t h b l a c k s p r u c e s t a n d s , r a n g i n g i n age from 50 t o 125 y e a r s . The f o r e s t f l o o r was made up o f a con t inuous man t l e of mosses, p r i n c i p a l l y f e a t h e r mosses w i t h some Sphagnum. S t a n d s o f quaking a spen o c c u r r e d on some s l o p e s and were c h a r a c - t e r i z e d b y a s t r i k i n g d e c r e a s e i n moss c o v e r . The a r e a i s one of r e l a t i v e l y g e n t l e r e l i e f , w i t h rounded r i d g e s and e l e v a t i o n s r a n g i n g from 210 t o 980 m . S o i l s a r e s i l t loam and formed i n w i n d - d e p o s i t e d l o e s s . Ridges and upper s o u t h s l o p e s a r e f r e e of p e r m a f r o s t ; i n o t h e r l o c a t i o n s , s o i l s g e n e r a l l y have a p e r m a f r o s t t a b l e w i t h i n 40 t o 50 cm o f t h e s u r f a c e .

S h o r t l y a f t e r t h e f i r e was c o n t r o l l e d , e i g h t p l o t s were e s t a b - l i s h e d i n b l a c k s p r u c e a r e a s f o r i n t e n s i v e s t u d y o f t h e e c o l o g i c a l e f f e c t s o f t h e f i r e . These p l o t s were a r r a n g e d i n t h r e e s e t s l o c a t e d on t h e r i d g e t o p and middle and lower s l o p e s . Two p l o t s e t s c o n s i s t e d o f an unburned c o n t r o l , a l i g h t l y burned s t a n d and a h e a v i l y burned s t a n d . The o t h e r s e t (on t h e r i d g e t o p ) c o n t a i n e d o n l y a h e a v i l y burned s t a n d and a n unburned c o n t r o l . Three a d d i t i o n a l p l o t s were e s t a b l i s h e d 1 y e a r a f t e r t h e f i r e ( June 1 9 7 2 ) - - a h e a v i l y burned s t a n d and an unburned c o n t r o l i n a s p e n , p l u s a n o t h e r unburned c o n t r o l i n b l a c k s p r u c e .

Although c e r t a i n p o r t i o n s o f t h i s s t u d y a r e c o n t i n u i n g , r e s u l t s r e p o r t e d h e r e a r e main ly f o r t h e f i r s t 3 y e a r s a f t e r t h e f i r e (1972-74) .

2 3 ~ h i s sec t ion was prepared by C . T. Dyrness, Supervisory S o i l S c i e n t i s t , USDA Forest Service, P a c i f i c Northwest Forest and Range Experiment S ta t ion , I n s t i t u t e of Northern Forestry, Fairbanks, Alaska.

Examinat ion o f s o i l a f t e r t h e f i r e i n d i c a t e d t h a t m o i s t lower f o r e s t f l o o r l a y e r s had minimized t h e impact o f t h e f i r e on t h e s o i l . O the r t h a n i n f i r e l i n e s , p a t c h e s o f b a r e m i n e r a l s o i l were r a r e , even i n h e a v i l y burned a r e a s . Measurements of burned f o r e s t f l o o r t h i c k n e s s i n d i c a t e d g r e a t e s t f i r e e f f e c t s o c c u r r e d where f o r e s t f l o o r s were t h i c k e s t ; s t a r t i n g w i t h an unburned t h i c k n e s s of 28 .7 cm, ave rage r e d u c t i o n s were 1 0 . 3 cm f o r h e a v i l y burned a r e a s and 5 .7 cm f o r l i g h t l y burned a r e a s . I n o t h e r words, even i n h e a v i l y burned a r e a s an ave rage o f a lmost t w o - t h i r d s of t h e f o r e s t f l o o r remained a f t e r b u r n i n g . Weight and b u l k d e n s i t y o f f o r e s t f l o o r samples were a l s o de te rmined ; however, no s t a t i s t i c a l l y s i g n i f i c a n t e f f e c t of t h e f i r e cou ld be de te rmined . I n view of t h e r a t h e r sha l low dep th o f b u r n i n g i n t h e f o r e s t f l o o r , i t i s pe rhaps n o t s u r p r i s i n g t h a t t h e bu rn ing had no d i s - c e r n a b l e e f f e c t on chemica l p r o p e r t i e s o f t h e m i n e r a l s o i l . Ca t ion exchange c a p a c i t y , pH, exchangeable Ca, Mg, and K , a v a i l - a b l e P , and t o t a l N were de termined on samples from t h e s u r f a c e 15 cm o f m i n e r a l s o i l i n burned and unburned a r e a s , b u t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s between t h e a r e a s .

The r e d u c t i o n o f f o r e s t f l o o r t h i c k n e s s and b l a c k e n i n g o f t h e s u r f a c e by f i r e c a u s e s h i g h e r s o i l t e m p e r a t u r e s . Most s t u d i e s have i n d i c a t e d t h a t s u r f a c e s o i l s which have been r e c e n t l y burned warm up more q u i c k l y a t t h e beg inn ing o f t h e growing s e a s o n and a r e s u b s t a n t i a l l y warmer t h a n unburned s o i l s . Th i s r e l a t i o n s h i p a l s o proved t r u e i n t h e p r e s e n t s t u d y ; 1 y e a r a f t e r t h e f i r e , t h e s o i l t e m p e r a t u r e a t a dep th o f 10 cm reached a maximum of 1 0 . S ° C on J u l y 20 i n a burned a r e a . I n t h e unburned c o n t r o l , t h e maximum t e m p e r a t u r e was o n l y 6OC, and t h e peak was de layed u n t i l September 13 .

I n i n t e r i o r Alaska one o f t h e most i m p o r t a n t consequences of i n c r e a s e s i n s o i l t e m p e r a t u r e caused by f i r e i s s t e p p e d up perma- f r o s t m e l t i n g . Such thawing s u b s t a n t i a l l y i n c r e a s e s t h e amount o f a v a i l a b l e s o i l n u t r i e n t s and s o i l w a t e r . On t h e Wickersham Dome f i r e s i t e , change i n t h e r a t e o f thawing was p a r t i c u l a r l y d r a m a t i c ; 1 y e a r a f t e r t h e f i r e , t h e a c t i v e l a y e r was 62 cm t h i c k i n t h e burned a r e a and o n l y 42 cm i n t h e unburned c o n t r o l . By t h e 3d y e a r , t h e a c t i v e l a y e r had i n c r e a s e d t o 84 cm i n t h e burned a r e a and 47 cm i n t h e unburned c o n t r o l . On f i r e l i n e s , where v i r t u a l l y a l l s u r f a c e i n s u l a t i o n had been removed, t h e r a t e of p e r m a f r o s t drop was a lmost doub led ; 3 y e a r s a f t e r t h e f i r e , t h e a c t i v e l a y e r i n t h e f i r e l i n e s was 132 cm t h i c k .

D e s p i t e s u b s t a n t i a l changes i n t h e m i c r o c l i m a t e caused by f i r e , e s p e c i a l l y i n and around t h e f o r e s t f l o o r , s t u d i e s o f aboveground m a c r o c l i m a t i c pa ramete r s d i d n o t d i s c l o s e measurable d i f f e r e n c e s between burned and unburned a r e a s . For example, p a t t e r n s of snow accumula t ion and snowmelt were n o t s u b s t a n t i a l l y d i f f e r e n t i n a burned a r e a t h a n i n an unburned a r e a . L ikewise , s t a n d a r d measurements o f a i r t e m p e r a t u r e d i d n o t d i s c l o s e a d i f f e r e n c e between burned and unburned a r e a s .

U n f o r t u n a t e l y , l i t t l e work has been done i n i n t e r i o r Alaska on t h e e f f e c t s o f w i l d f i r e and f i r e s u p p r e s s i o n on q u a l i t y of s t r e a m w a t e r . There a r e s p e c u l a t i o n s t h a t i n c r e a s e s i n e r o s i o n and r u n o f f caused by f i r e a r e a t a minimum i n n o r t h e r n a r e a s ,

b u t d a t a t o back t h i s up a r e l a c k i n g . To o b t a i n an i n d i c a t i o n of t h e e f f e c t s of t h e Wickersham Dome f i r e on s t r e a m s , we sampled Washington Creek bo th above and below t h e f i r e on t h e day t h e f i r e was c o n t r o l l e d , 1 week a f t e r c o n t r o l , and 2 weeks a f t e r . The day t h e f i r e was c o n t r o l l e d , suspended sediment c o n t e n t of t h e s t r eam was about 300-500 m g / l i t e r . A f t e r t h e Bureau of Land Management c o n s t r u c t e d wa te r b a r s on t h e f i r e l i n e s , t h e sediment c o n t e n t dropped t o a maximum v a l u e o f 19 m g / l i t e r 1 week a f t e r c o n t r o l . A smal l i n c r e a s e i n c o n c e n t r a t i o n of phosphate i n t h e s t r eam wate r was measured a f t e r a p p l i c a t i o n s of r e t a r d a n t s ; however, c o n c e n t r a t i o n s o f n i t r o g e n were t h e same above and below t h e burned a r e a .

Development of v e g e t a t i o n a f t e r t h e f i r e was, a s would be expec ted , c l o s e l y t i e d t o s e v e r i t y of t h e f i r e . On a l i g h t l y burned b l a c k sp ruce p l o t 40 p e r c e n t of t h e ground v e g e t a t i v e cover was s t i l l a l i v e a f t e r t h e f i r e . This i n c r e a s e d t o a t o t a l o f 7 0 p e r c e n t cover 3 y e a r s a f t e r t h e f i r e (August 1974) . Con- s i d e r a b l e amounts of mosses and CZadonia l i c h e n s s u r v i v e d t h e f i r e and g r e a t l y c o n t r i b u t e d t o i t s r a p i d p o s t f i r e r ecovery . Although many b l a c k sp ruce s e e d l i n g s and s a p l i n g s were a l i v e a f t e r t h e f i r e , t h e m a j o r i t y of t h e s e d i e d dur ing t h e subsequent 3 y e a r s , l e a v i n g on ly 61/ha. Spruce s e e d l i n g s , however, germinated i n l a r g e numbers; n e a r l y 40,00O/ha were recorded i n 1974.

In c o n t r a s t , r ecovery of v e g e t a t i o n on h e a v i l y burned b l a c k sp ruce p l o t s has been much s lower . No c l imax mosses and l i c h e n s su rv ived t h e f i r e ; consequen t ly , moss and l i v e r w o r t cover was low a f t e r 3 y e a r s and was made up e x c l u s i v e l y of t h e invaders Marchantia polymorpha and Ceratodon purpurea. Herbaceous cover recovered a t a f a s t e r r a t e and reached about 15-20 p e r c e n t a f t e r 3 y e a r s - - s u b s t a n t i a l l y h i g h e r than t h a t i n t h e unburned c o n t r o l . P r i n c i p a l herbaceous s p e c i e s i n t h e s e e a r l y p o s t f i r e y e a r s were Equisetum syZvaticum andEpiZobiurn angustifolium, both p r e s e n t i n t h e unburned c o n t r o l . Response of sh rubs t o f i r e on h e a v i l y burned p l o t s has been mixed. On one p l o t , SaZix scouleriana sprou ted r a p i d l y a f t e r t h e f i r e and by t h e 3d y e a r had t h r e e t imes t h e b a s a l a r e a of t h e unburned c o n t r o l . I n o t h e r a r e a s , however, s p r o u t i n g of shrubs was l e s s v igorous ; a f t e r 3 y e a r s , d e n s i t i e s were s t i l l a p p r e c i a b l y lower than on t h e unburned c o n t r o l .

One of t h e most s i g n i f i c a n t f i n d i n g s of our s t u d i e s of revege- t a t i o n was t h a t ve ry few of t h e p l a n t s p e c i e s appear ing soon a f t e r a f i r e a r e i n v a d e r s . The g r e a t m a j o r i t y a r e s p e c i e s t h a t were p r e s e n t i n t h e p r e f i r e s t a n d and reproduce v e g e t a t i v e l y from underground p l a n t p a r t s s u r v i v i n g t h e f i r e . This p rocess of vege- t a t i v e reproduc t ion was e s p e c i a l l y s t r i k i n g i n t h e h e a v i l y burned aspen s t a n d . During t h e 1st y e a r a f t e r t h e f i r e , t h e r e were n e a r l y 200,000 aspen shoo t s p e r h e c t a r e . Rosa acicuZaris a l s o g r e a t l y i n c r e a s e d i t s cover a f t e r t h e f i r e by means of stem and r o o t s h o o t s . Because most of t h e s e underground p a r t s t h a t a r e a c t i v e i n p o s t f i r e r eproduc t ion a r e l o c a t e d i n t h e o r g a n i c f o r e s t f l o o r l a y e r s , d e p t h of burning becomes of overwhelming importance i n c o n t r o l l i n g t h e n a t u r e of e a r l y s u c c e s s i o n a l s t a g e s . With i n c r e a s i n g dep ths of burn , more and more of t h e s e s t r u c t u r e s w i l l

be e l i m i n a t e d u n t i l , w i t h b a r e m i n e r a l s o i l , o n l y s p a r s e v a s c u l a r p l a n t cove r w i l l be p r e s e n t d u r i n g t h e 1st y e a r a f t e r b u r n i n g .

Some workers have s p e c u l a t e d t h a t , a s a r e s u l t o f warmer s i t e s and a c c e l e r a t e d n u t r i e n t c y c l i n g , e a r l y s t a g e s o f p o s t f i r e S U C -

c e s s i o n i n t h e Alaska t a i g a would be marked by i n c r e a s e s i n p r imary p r o d u c t i v i t y . To t e s t t h i s a s sumpt ion , we unde r took a l i m i t e d sampl ing program o f annua l biomass and l i t t e r f a l l a t t h e Wickersham Dome s t u d y s i t e . Biomass a t t h e end of t h e 3d y e a r a f t e r t h e f i r e was ex t r eme ly v a r i a b l e , r a n g i n g from a low o f 33 g / m 2 on a h e a v i l y burned b l a c k s p r u c e p l o t t o a h i g h of 804 g / m 2 on t h e h e a v i l y burned a spen p l o t . Although approx ima te ly 60 p e r c e n t o f t h e t o p f i g u r e was c o n t r i b u t e d by aspen s p r o u t s , Cera todon, Marchan t i a , EpiZobium, and CaZamagrostCs a l s o had s i z a b l e amounts o f b iomass . D e s p i t e t h e f a c t t h a t t h e a spen s p r o u t s were h e a v i l y browsed, t h e y c o n t i n u e d t o grow w e l l and t h e browsing a p p a r e n t l y encouraged t h e development o f l a t e r a l b r a n c h e s . T h i s v e r y h i g h p r o d u c t i o n of a v a i l a b l e browse i l l u s t r a t e s t h e p o s s i b l e v a l u e o f f i r e i n t h e p r o d u c t i o n o f w i l d l i f e h a b i t a t .

To f u l l y u n d e r s t a n d t h e e f f e c t s of f i r e on n u t r i e n t c y c l i n g , we must measure b o t h l i t t e r f a l l and r a t e s o f l i t t e r decompos i t ion . I n t h e burned b l a c k s p r u c e p l o t s , l i t t e r f a l l o r i g i n a t e d p r i m a r i l y from s t a n d i n g dead t r e e s and w i l l o w s . L i t t e r f a l l i n l i g h t l y burned p l o t s was h e a v i e s t t h e 2d y e a r a f t e r t h e f i r e when i t ave raged abou t 20 g / m 2 ( v e r s u s 10 g / m Z i n t h e unburned c o n t r o l , and 7 g / m 2 i n h e a v i l y burned p l o t s ) . During t h e 3d y e a r a f t e r b u r n i n g , l i t t e r f a l l d e c r e a s e d i n b o t h burned b l a c k s p r u c e a r e a s . A s would be e x p e c t e d , 3 i t t e r p r o d u c t i o n i n t h e burned aspen p l o t was v e r y h i g h (118 g/m p e r y e a r ) because o f abundant s p r o u t s .

Ra te s o f l i t t e r decomposi t ion were e s t i m a t e d from c o n t e n t s o f l i t t e r b a g s p l a c e d on t h e f o r e s t f l o o r i n b o t h unburned and h e a v i l y burned b l a c k s p r u c e s t a n d s . The ny lon mesh bags c o n t a i n e d t h r e e t y p e s o f l i t t e r : b l a c k s p r u c e n e e d l e s and b l u e b e r r y and Labrador- t e a l e a v e s . P r e l i m i n a r y r e s u l t s i n d i c a t e d t h a t r a t e s o f decomposi- t i o n were t h e same i n burned and unburned s t a n d s . Black s p r u c e n e e d l e s and L a b r a d o r - t e a l e a v e s had abou t 3 1 - p e r c e n t we igh t l o s s a f t e r 2 y e a r s ; b l u e b e r r y l e a v e s l o s t 37 p e r c e n t o f t h e i r we igh t .

Black s p r u c e i s a s p e c i e s i d e a l l y s u i t e d t o r e s e e d an a r e a d i s t u r b e d by f i r e . S i n c e i t s cones a r e s e m i s e r o t i n u s , t h e f i r e - k i l l e d t r e e can c o n t i n u e t o r e l e a s e c o n s i d e r a b l e q u a n t i t i e s of s e e d f o r y e a r s . To compare q u a n t i t y and q u a l i t y o f s e e d from burned s i t e s w i t h t h a t o f s e e d from unburned s i t e s , we fo l lowed s e e d d i s p e r s a l and s e e d l i n g e s t a b l i s h m e n t i n l i g h t l y and h e a v i l y burned s t a n d s and a n unburned c o n t r o l . During t h e 1s t y e a r a f t e r t h e f i r e , b l a c k s p r u c e s e e d f a l l i n t h e burned p l o t s ( ave rage of 331/m2) was a lmost f o u r t imes a s g r e a t a s t h a t i n t h e unburned c o n t r o l (85/m2). D e s p i t e more s e e d from burned t r e e s , t i m i n g of s e e d d i s p e r s a l was t h e same i n burned and unburned s t a n d s . Peak d i s p e r s a l o c c u r r e d i n midsummer d u r i n g p e r i o d s o f h i g h t e m p e r a t u r e and low humid i ty . Seed q u a l i t y was a p p a r e n t l y a d v e r s e l y a f f e c t e d by h i g h t e m p e r a t u r e s . T e s t i n g o f s e e d d i s p e r s e d t h e 1st y e a r a f t e r t h e f i r e showed h i g h e r p e r c e n t a g e s o f g e r m i n a t i o n i n t h e unburned c o n t r o l and l i g h t l y burned s t a n d s t h a n i n t h e h e a v i l y burned a r e a s .

A l s o , t h e ge rmina t ion c a p a c i t y o f s e e d from f i r e - k i l l e d t r e e s appeared t o d e c r e a s e w i t h t ime . Germinat ion f o r f i l l e d s e e d s ave raged 90 , 65 , and 32 p e r c e n t f o r s e e d s c o l l e c t e d from burned b l a c k s p r u c e t r e e s 1, 2 , and 3 y e a r s a f t e r t h e f i r e , r e s p e c t i v e l y . Even i f o n l y germinable s e e d a r e c o n s i d e r e d , s e e d l i n g e s t a b l i s h - ment a p p e a r s t o be d i f f i c u l t on burned s i t e s . Counts i n d i c a t e d t h a t on burned p l o t s o n l y 1 p e r c e n t o f germinable s e e d s a c t u a l l y developed i n t o e s t a b l i s h e d s e e d l i n g s .

To more c l o s e l y f o l l o w t r e n d s i n g e r m i n a t i o n and e s t a b l i s h m e n t of t r e e s e e d l i n g s i n r e c e n t l y burned a r e a s , we c a r r i e d o u t an a r t i f i c i a l s e e d i n g exper iment t h e summer o f 1972. Black s p r u c e , w h i t e s p r u c e , and pape r b i r c h s e e d s were sown i n e a r l y June on p l o t s hav ing a n o r t h and s o u t h a s p e c t . B i r c h ' g e r m i n a t i o n r eached a peak i n mid-June t o l a t e June on b o t h n o r t h - and s o u t h - f a c i n g s l o p e s . Germinat ion o f bo th w h i t e and b l a c k s p r u c e s e e d peaked i n l a t e June on t h e n o r t h s l o p e , b u t t h e ge rmina t ion p e r i o d was more d i f f u s e and s p r e a d o u t on t h e s o u t h s l o p e . S e e d l i n g m o r t a l i t y o c c u r r e d e a r l i e r on t h e s o u t h s l o p e p l o t s and appeared t o be main ly caused by h i g h t e m p e r a t u r e s and d e s i c c a t i o n . F a c t o r s c a u s i n g s e e d l i n g m o r t a l i t y o n t h e n o r t h s l o p e werebrowsing , damping- o f f , and smothe r ing by competing v e g e t a t i o n . By September, however, t h e p r o p o r t i o n o f s u r v i v i n g s e e d l i n g s was approx ima te ly t h e same on b o t h a s p e c t s . Pe rcen tage of s e e d l i n g s u r v i v a l was h i g h e s t f o r b l a c k s p r u c e , second f o r w h i t e s p r u c e , and lowes t f o r p a p e r b i r c h .

S t u d i e s o f an ima l s a f t e r t h e f i r e focused on i n s e c t s , m i c r o t i n e r o d e n t s , and snowshoe h a r e s . Numbers of s p i d e r s , Col lembola , m i t e s , C o l e o p t e r a , and o t h e r a r t h r o p o d s were fo l lowed i n burned and unburned a r e a s d u r i n g t h e summers o f 1972 and 1973. During b o t h y e a r s , t h e burned a r e a s u p p l i e d more c a p t u r e d specimens t h a n t h e unburned. I t does n o t , however, n e c e s s a r i l y f o l l o w t h a t i n s e c t numbers were h i g h e r i n t h e burned a r e a ; i t might s imply i n d i c a t e a h i g h e r deg ree o f a r t h r o p o d a c t i v i t y . The numbers c a p t u r e d i n a l l c a t e g o r i e s e x c e p t s p i d e r s d e c r e a s e d a p p r e c i a b l y i n 1973. T h i s d e c l i n e i n numbers i n most a r t h r o p o d p o p u l a t i o n s was a t t r i b u t e d t o p r e d a t i o n by s p i d e r s .

Voles were l i v e t r a p p e d i n a h e a v i l y burned a r e a and an a d j a c e n t unburned c o n t r o l f o r t h e f i r s t 3 y e a r s a f t e r t h e f i r e . D e s p i t e t h e p r e s e n c e o f numerous n o r t h e r n r ed -backed v o l e s i n t h e unburned a r e a , i t s a c t i v i t y i n t h e burned a r e a was v e r y low and s t r i c t l y conf ined t o t h e p e r i o d from l a t e J u l y t o e a r l y November i n 1972 and 1973. S t a r t i n g i n J u l y 1974, t h e p o p u l a t i o n o f r ed -backed v o l e s i n t h e burned a r e a i n c r e a s e d s u b s t a n t i a l l y and some o v e r w i n t e r e d t h e r e f o r t h e f i r s t t ime i n 1974-75. The t u n d r a v o l e was a p p a r e n t l y v e r y r a r e i n t h e unburned b l a c k s p r u c e s t a n d s where o n l y one animal was e v e r c a u g h t . Tundra v o l e s , however, e n t e r e d t h e burned a r e a i n e a r l y s p r i n g o f 1974, and t h e p o p u l a t i o n i n c r e a s e d u n t i l mid- August when a modera te d e c l i n e s e t i n . By t h e 3d y e a r a f t e r t h e f i r e , b o t h r ed -backed v o l e s and t u n d r a v o l e s had a p p a r e n t l y e s t a b - l i s h e d r e s i d e n t p o p u l a t i o n s i n t h e burned a r e a .

The f i r e c o i n c i d e d w i t h t h e h i g h p o i n t i n t h e 1 0 - y e a r p o p u l a t i o n c y c l e o f t h e snowshoe h a r e . Consequent ly , i n t h e f a l l o f 1971, t h e h a r e s consumed l a r g e q u a n t i t i e s o f w i l low s p r o u t s t h a t were a l r e a d y

coming up i n t h e burned a r e a . During t h e w i n t e r , when t h e s u p p l y o f s p r o u t s was e x h a u s t e d , t h e h a r e s f e d on c h a r r e d b a r k . The p o p u l a t i o n c o n t i n u e d a t h i g h l e v e l s u n t i l 1973 and consumed a l l t h e a v a i l a b l e hardwood browse i n t h e unburned c o n t r o l and f o r a t l e a s t 200 m i n t o t h e burned a r e a . I n 1974, d e n s i t y o f h a r e s d e c r e a s e d and i n t e n s i t y o f browsing f e l l o f f . Trapping d a t a i n d i c a t e d t h a t t h e p o p u l a t i o n o f snowshoe h a r e s v a r i e d from a h i g h o f s i x h a r e s p e r h e c t a r e i n t h e fa , l l o f 1971 t o a low o f 0.12 h a r e / h a i n t h e s p r i n g of 1975. D e s p i t e t h e f a c t t h a t some h a r e s were t r a p p e d i n t h e burned a r e a , t h e r e appea red t o be no permanent r e s i d e n t s t h e r e even 3 y e a r s a f t e r t h e f i r e .

R e s u l t s o f t r a p p i n g and a n a l y s i s o f stomach c o n t e n t s r e v e a l e d t h a t h a r e s m i g r a t e s e a s o n a l l y and s u b s t a n t i a l l y change t h e i r d i e t . I n summer, t h e y p r e f e r open a r e a s where b l u e b e r r y , lowbush c r a n b e r r y , and herbaceous p l a n t s a r e most p l e n t i f u l . I n t h e w i n t e r , h a r e s move back i n t o dense b l a c k s p r u c e s t a n d s where t h e y f e e d on s p r u c e , w i l l o w , and a l d e r . Even heavy browsing on hardwoods a p p e a r s t o be b e n e f i c i a l ; i t s t i m u l a t e s l a t e r a l b ranch ing and , hence , g r e a t e r p r o d u c t i v i t y .

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