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Overview of UAA-ENRI’s Studies of the Spruce Bark Beetle Epidemic ,

Kenai Peninsula, Alaska

byby

Vernon J. LaBau, Univ. of AK., ENRIVernon J. LaBau, Univ. of AK., ENRI

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Forest Inventory and AssessmentUniversity of Alaska, 1997 & 1998 Two concurrent studies by UAA, ENRI Two concurrent studies by UAA, ENRI

oriented to determine:oriented to determine: Magnitude of spruce bark beetle killMagnitude of spruce bark beetle kill Phytomass present by vegetation class Phytomass present by vegetation class Natural regeneration situationNatural regeneration situation Health of residual trees-post beetle attackHealth of residual trees-post beetle attack Mortality sampling plot efficacyMortality sampling plot efficacy Criteria for modeling forest firesCriteria for modeling forest fires Result- Six papers, summarized hereinResult- Six papers, summarized herein

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Background --A major Outbreak

During the mid to late 1990s, one of the During the mid to late 1990s, one of the largest forest bark beetle outbreaks ever largest forest bark beetle outbreaks ever experienced anywhere in the world experienced anywhere in the world occurred in Alaska.occurred in Alaska.

More than 1 million acres were attacked in More than 1 million acres were attacked in 1996 alone, primarily on the Kenai 1996 alone, primarily on the Kenai Peninsula south of Anchorage. Peninsula south of Anchorage.

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Cumulative Beetle Impact to 1998

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Background-- Species Involved Attacker--Attacker--spruce bark beetle

(Dendroctonus rufipennis (Kirby))

Affected tree species

white spruce

((Picea glauca (Moench) Voss) and Lutz spruce

(Picea Xlutzii Little)

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Background --Funding Source

Funding came from:Funding came from: The UAA Natural Resources Fund

$27,000 for the 1997 Study$25,000 for the 1998 Study

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Background--1997 ObjectivesDetermine the area of High, Moderate and Low

intensity bark beetle impact strata.Determine the extent the bark beetle has impacted

growing stock, especially for white and Lutz spruce. What size trees were being attacked? What percent of the trees were being impacted?

Determine the level of regeneration in the above impact areas, especially for white and Lutz spruce. Is there any indication that grass is inhibiting regeneration of spruce where the spruce over-story has been killed by beetle attack.

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Background--1998 Objectives

Expand on the 1997 study, primarily to collect data to develop a forest fire fuels model, as well as collect additional data on mortality, total vegetation phytomass and down wood biomass.

Expand the study sample size and ground plot configuration to evaluated the efficacy of sampling plot designs in capturing mortality information.

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Methodology--The Study Design

Two-Phase, Double Sampling Two-Phase, Double Sampling

Phase 1, Photo Stratification (2600 Points)Phase 1, Photo Stratification (2600 Points)

Forest typeForest typeBeetle attack intensityBeetle attack intensity

(from S&PF/ADNR Aerial Survey maps)(from S&PF/ADNR Aerial Survey maps)OwnershipOwnership

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Methodology-- Study Design Establishing Study Impact Intensity StrataEstablishing Study Impact Intensity Strata

High Impact: Photo point falling inside a Survey mapped insect attack polygon.

Moderate Impact: Photo point falling within one mile of a Survey map attack polygon.

Low Impact: Photo point beyond one mile of a polygon, but within one mile of a “dot” on the Aerial Survey maps, indicating an area of isolated attacks.

No Impact: Photo point beyond one mile of a polygon or “dot” from Aerial Survey maps.

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Methodology-- Study Design

Phase 2 Data Collection (40 Ground Plots)Phase 2 Data Collection (40 Ground Plots)Standard Forest Inventory DataStandard Forest Inventory Data

• Species, diameter, height, crown dataSpecies, diameter, height, crown dataSpecialized Mortality Tally (.6 hectare)Specialized Mortality Tally (.6 hectare)Forest Health Damage AssessmentForest Health Damage AssessmentHorizontal-Vertical Profile of VegetationHorizontal-Vertical Profile of VegetationRegeneration AssessmentRegeneration AssessmentDowned Wood AssessmentDowned Wood AssessmentFuels Assessment (laddering, etc.)Fuels Assessment (laddering, etc.)

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1.2 Million Acresin the Study Area

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One HectareGround Plots

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Establishing Tree Health Criteria

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Taking the Ground Plots

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Photos of Beetle Kill Near Homer

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Results: Magnitude of spruce bark beetle kill

By 1998, 58% of forests were under high or moderate By 1998, 58% of forests were under high or moderate impact and 78% of all forest land (conifer, mixed, and impact and 78% of all forest land (conifer, mixed, and hardwood) was impacted by the bark beetle.hardwood) was impacted by the bark beetle.

The stratification system used in this study worked well, The stratification system used in this study worked well, yielding a sampling error of only 5.3% for the 1.2 million yielding a sampling error of only 5.3% for the 1.2 million acres of Kenai area forest under study.acres of Kenai area forest under study.

41% of all spruce alive in 1992 were dead in 1998.41% of all spruce alive in 1992 were dead in 1998.

On some plots, virtually 100% of all spruce killed.On some plots, virtually 100% of all spruce killed.

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Chart of Beetle Impacts

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Results:Health of residual spruce trees

Only 4.9% of the residual spruce were Only 4.9% of the residual spruce were judged to have health at risk. 56% were judged to have health at risk. 56% were in good health.in good health.

About 25% of the residual spruce were About 25% of the residual spruce were under attack by bark beetles in 1998.under attack by bark beetles in 1998.

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Results:Health of residual birch trees

Almost 75% of the residual birch exhibited risky Almost 75% of the residual birch exhibited risky or moderately risky tree health.or moderately risky tree health.

The paper birch was found to have almost four The paper birch was found to have almost four times as much basal area in the “at risk” tree times as much basal area in the “at risk” tree health class as the spruce.health class as the spruce.

The primary vectors of “Risk” for the paper birch The primary vectors of “Risk” for the paper birch were conks on the roots or lower boles and crown were conks on the roots or lower boles and crown dieback exceeding 33% of the crown.dieback exceeding 33% of the crown.

About 2/3rds of the birch regeneration exhibited About 2/3rds of the birch regeneration exhibited heavy moose browsing in 1998.heavy moose browsing in 1998.

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Result: Natural regeneration findings:

Regeneration of the spruce was marginal, from 130 to 400 trees Regeneration of the spruce was marginal, from 130 to 400 trees per acre, but nearly absent in some areas due to grass invasion per acre, but nearly absent in some areas due to grass invasion and competition. and competition.

Regeneration of birch was quite good, in many places over Regeneration of birch was quite good, in many places over 1000 trees per acre. However, as noted before, 67% of the 1000 trees per acre. However, as noted before, 67% of the birch seedlings had been heavily browsed by moose.birch seedlings had been heavily browsed by moose.

Grass phytomass in High and Moderate “Impact” strata was up to four times greater than in the Low and No “Impact” strata, supporting the theory that grass invades as overstory is killed.

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Example of Grass Invasion after Tree Kill

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Chart of Phytomass Distribution

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Result: Other interesting findings:

Understory phytomass was only about 2% of that found in the overstory. Almost half of the understory phytomass occurred in shrub vegetation.

There was evidence of a decrease in moss phytomass as the crown cover disappeared due to the bark beetles killing the spruce overstory.

I.e. Less moss in the “High” impact stands, and more moss in the “Low” and “No”

Impact stands, the latter having more closed canopy.

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Chart of Under-story Phytomass

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Result: Down Wood findings:

The bark beetle killed trees were just beginning to fall down in 1998.

Fall-down was more in evidence in the High “Impact” strata.

The down wood component should see significant increase in phytomass in the near future as more beetle killed spruce fall.

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A Textbook Condition for Ecological Studies

The bark beetle epidemic in south-central The bark beetle epidemic in south-central Alaska during the 1990s provided plethora Alaska during the 1990s provided plethora of unique ecological information on forest of unique ecological information on forest dynamics and vegetative succession, some dynamics and vegetative succession, some of which we were fortunate to capture in of which we were fortunate to capture in these studies. these studies.

There is certainly even more information to There is certainly even more information to be mined from this event in various other be mined from this event in various other disciplines of nature and sociology. disciplines of nature and sociology.

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A Closing Thought to Remember

Crunch, crunch, crunch,Crunch, crunch, crunch,listen to 'em munch,listen to 'em munch, it's always time for lunch, it's always time for lunch, in the deep, dark, forest. in the deep, dark, forest.

Courtesy of Al HarrisCourtesy of Al Harris