Deer & Allegheny Plateau Forests
Transcript of Deer & Allegheny Plateau Forests
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Deer & Allegheny Plateau Forests
Alejandro A. Royo
US Forest Service Northeastern Research Station
Warren, PA
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Deer & Allegheny Plateau Forests
• Short history of PA’s deer situation
• Impacts of deer on forest vegetation
• Recognizing and managing deer impacts
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Deer & Allegheny Plateau Forests
• Short history of PA’s deer situation
• Impacts of deer on forest vegetation
• Recognizing and managing deer impacts
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Deer Herbivory
•
Deer browsing –
THE major factor affecting forest regeneration in PA since the 1920s
•
Deer have direct
and indirect
effects on
forest regeneration
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Dee
r pe
r sq
uare
mile
PA GameComm. Goal
Historical Estimates
Deer Population during 20th CenturyDeer Population during 20th Century
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Early Impacts
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Farmers were first to complain of overabundance
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Hobblebush and shrub layer significantly altered, including in old growth
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Alters recovery after disturbance
William S. Justice, USDA Plants Databse
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Deer Population during 20th Century
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Dee
r pe
r sq
uare
mile
PA GameComm. Goal
Historical Estimates
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Half of all harvests failed to regenerate
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Fencing fixed 87% of failed cuts
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Advanced regeneration was the key
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However...’success’ was often monoculture
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Deer & Allegheny Plateau Forests
• Short history of PA’s deer situation
• Impacts of deer on forest vegetation
• Recognizing and managing deer impacts
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Forestry Sciences Lab. Irvine, PA
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Deer BrowsingDeer Browsing Direct Consumptive ImpactsDirect Consumptive Impacts
•Impact species composition, abundance and growth
–
Over time, selective browsing on preferred species reduces species richness and shifts species composition towards unpreferred
& browse-
resilient species
Woody Tree
Species
Tolerant Herbs/ Shrubs
Many Forbs/ Shrubs
-
-
+
11ºº
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Species Food Preference / Resilience to Browsing by DeerSpp Pref Resil Spp Pref ResilBC L L CUC H LRM H L HEM M-H LSM H L PC H LAB M-L H STM M-L HWA H L RUB H M-HY-P H L HSF Not HYB M M NYF Not HBB M M G / S M-L H
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Species Food Preference / Resilience to Browsing by DeerSpp Pref Resil Spp Pref ResilBC L L CUCCUC HH LLRMRM HH LL HEMHEM MM--HH LLSMSM HH LL PCPC HH LLAB M-L H STM M-L HWAWA HH LL RUBRUB HH MM--HHYY--PP HH LL HSF Not HYB M M NYF Not HBB M M G / S M-L H
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Species Food Preference / Resilience to Browsing by DeerSpp Pref Resil Spp Pref ResilBCBC LL LL CUC H LRM H L HEM M-H LSM H L PC H LABAB MM--LL HH STMSTM MM--LL HHWA H L RUB H M-HY-P H L HSFHSF NotNot HHYB M M NYFNYF NotNot HHBB M M G / SG / S MM--LL HH
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Boulders as a Bioassay and a RefugiaBoulders as a Bioassay and a Refugia
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Banta, Royo, Carson & Kirschbaum
(2005) Nat. Areas Jour.
Bouldertop Communities Had Greater Bouldertop Communities Had Greater Abundance of Several Woody SpeciesAbundance of Several Woody Species
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America
n Bee
chBlac
k Cherr
y
Hemlock
Hornbea
mMountai
n Map
leRed
Map
leStri
ped M
aple
Sweet B
irch
Witch H
azel
Yellow B
irch
Overal
l
Overal
l, Subtra
cting B
eech
On BouldersOff Boulders
**
**
**
**
* *
AVE
RA
GE
DEN
SITY
(#SA
PLIN
GS/
M2)
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•
A designed study, replicated at 4 NW PA locations
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4 deer densities enclosed in managed forests
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Each deer enclosure was 10% clearcut, 30% thinned, and 60% uncut
Experimental Manipulations of Experimental Manipulations of Deer Levels: Enclosure StudyDeer Levels: Enclosure Study
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Preferred Species Decrease in Preferred Species Decrease in AbundanceAbundance
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10
Spp Pref
Resil
PCPC HH
LL
Horsley et al. (2003) Ecol. Apps.
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UnpreferredUnpreferred
Species Increase Species Increase in Abundancein Abundance
10
64
Spp Pref
Resil
BCBC LL
LL
Horsley et al. (2003) Ecol. Apps.
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Diversity Decreases
64
10
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Deer affected height growth•
Negative linear trend of decreasing height with increasing deer density for most species
10 20 38 64DEER DENSITY
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AV.
HT.
OF
TALL
EST S
EEDLI
NG
(FT.)
BCABSTM
10 YAT
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Deer affected height growth•
Negative linear trend of decreasing height with increasing deer density for most species
•
By year 10, some species had grown out of reach of deer.
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Deer affected stocking
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85% of regen was bc, pc, bi, and stmaple
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By 10 yrs in clearcuts–
Rubus, pc, bi, rm, be, sm, wa were less abundant at high deer density sites
–
fern, grass, and bc increased with deer
density•
Similar effects in thinnings and uncuts
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Indirect effect: Increase in browse-tolerant understory species leading to plant-plant competition (e.g. fern-tree seedling). Woody
Regen
Tolerant Herbs/ Shrubs
+ -22ºº
Indirect Impact Indirect Impact –– Establishment of Dense Understory LayersEstablishment of Dense Understory Layers
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HayHay--scented Fern Abundance scented Fern Abundance Increased at High Deer Levels Increased at High Deer Levels
4
25
Horsley et al. (2003) Ecol. Apps.
Spp Pref
Resil
HSFHSF
NotNot HH
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Deer affected herbaceous cover & low shade
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Mea
n Se
edlin
g D
ensi
ty
(See
dlin
gs/m
2 )
* Royo, unpub. data
** Similar results Horsley 1993, Lyon and Sharpe 1995, Hill 1996, George and Bazzaz
1999, de la Cretaz
and Kelty
2002, and others
Fern
No Fern
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Hay-scented fern dominance across Allegheny Plateau
• Historically -
< 1% of understory.
• Present day:
•
33% of 499 sample plots across all of Pennsylvania.1
•
Estimated 130,000 -
180,000 acres in ANF alone.2,3
1.
McWilliams et al. 19952.
Allegheny National Forest Management Area 3.0 6,000 Plot Survey Report, 1995.
3.
Royo, unpub. data.
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Interfering Plants on the Allegheny National Forest
Interference Acres % all Acres
Fern130,173 -180,000
46%
Grass 61,176 21%Woody
Interference63,107 21%
Fern and/or Grass
162,138 57%
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Deer & Allegheny Plateau Forests
• Short history of PA’s deer situation
• Impacts of deer on forest vegetation
• Recognizing and managing deer impacts
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Deer Enclosure Study
•
Is this the worst case scenario we expected?
•
Why weren’t there complete regeneration failures at 64 dpsm?
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Reality check
Treatment Allegheny NF, early 80s avg. Deer study
Final harvest 4% 10%
Thinnings 13% 30%
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Alternate Reality Check
•
Home gardens and landscape plants provide ample deer food
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Deer Population484236302418126
Failure
Monoculture
Species Shift
Success
ExcessHigh Deer FoodMedium Deer FoodLow Deer Food
Competition
-- no./sq. mile
Very High
High
Moderate
Low
Very Low
Effect onRegeneration
DeerImpact
(5)
(4)
(3)
(2)
(1)
Deer Impact Index
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Deer Impact Level 1:
Inside a well maintained, woven-wire deer fence.
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Deer Impact Level 2:
Desirable regeneration common, widespread, of varying heights, and ...
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accompanied by a diverse herbaceous plant community.
Ferns, grasses, and other unpalatable/browse-resistant plant species are present but not common.
Photographer: Kenneth J. Sytsma
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10 20 38 64DEER DENSITY
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2
3
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6AV.
HT.
OF
TALL
EST
SEED
LING
(FT.
)
BCABSTM
10 YAT
Height varies both within and between species
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Preferred landscape plants survive
G.F. Russell –
USDA Plants Database
J.S. Peterson –
USDA Plants Database
JS Peterson –
USDA Plants Database
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Deer Impact Level 3:
Desirable regeneration present but heights are uniformly low. Browse evidence is widespread.
Ferns, grasses, and other unpreferred/browse resistantplant species common.
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Deer Impact Level 4: Desirable regeneration lacking, small. No stump sprouts. Few herbaceous plants. Widespread unpreferred/browse resistant plants, often browsed. Indistinct browse line.
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Deer Impact Level 5:
Desirable regeneration absent or nearly so. No stump sprouts. Only the hardiest browse-resistant and unpalatable plant species present. Distinct browse line.
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Deer & Allegheny Plateau Forests•
Past and present deer herbivory has often left its mark on the distribution and abundance of plant species.
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This has left a legacy direct and indirect impacts that make regenerating diverse stands challenging.
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This legacy has profoundly altered understory dynamics often leading to regeneration failures or monocultures.
• Species poor overstories/restricted seed supply.• Direct effect of overbrowsing.• Indirect effect of invasive understory plants species.• Indirect effect of increased seed predation.
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www.qdma.com
1500 A.D. ~ 10 mi2(McCabe and McCabe 1997)
Today’s densities< 15 deer/mi2
15 - 30 deer/mi2
30 - 45 deer/mi2
>45 deer/mi2
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Questions???Questions???