Overview of UAA-ENRI

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Overview of UAA-ENRIs Studies of the Spruce
Bark Beetle Epidemic ,Kenai Peninsula, Alaska

• by
• Vernon J. LaBau, Univ. of AK., ENRI

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Forest Inventory and AssessmentUniversity of
Alaska, 1997 1998

• Two concurrent studies by UAA, ENRI oriented to
  determine
• Magnitude of spruce bark beetle kill
• Phytomass present by vegetation class
• Natural regeneration situation
• Health of residual trees-post beetle attack
• Mortality sampling plot efficacy
• Criteria for modeling forest fires
• Result- Six papers, summarized herein

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Background --A major Outbreak

• During the mid to late 1990s, one of the largest
  forest bark beetle outbreaks ever experienced
  anywhere in the world occurred in Alaska.
• More than 1 million acres were attacked in 1996
  alone, primarily on the Kenai Peninsula south of
  Anchorage.

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Cumulative Beetle Impact to 1998
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Background-- Species Involved

• 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
• The UAA Natural Resources Fund
• 27,000 for the 1997 Study
• 25,000 for the 1998 Study

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Background--1997 Objectives

• Determine 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
• Phase 1, Photo Stratification (2600 Points)
• Forest type
• Beetle attack intensity
• (from SPF/ADNR Aerial Survey maps)
• Ownership

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Methodology-- Study Design

• Establishing 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)
• Standard Forest Inventory Data
• Species, diameter, height, crown data
• Specialized Mortality Tally (.6 hectare)
• Forest Health Damage Assessment
• Horizontal-Vertical Profile of Vegetation
• Regeneration Assessment
• Downed Wood Assessment
• 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 impact and 78 of all forest land
  (conifer, mixed, and hardwood) was impacted by
  the bark beetle.
• The stratification system used in this study
  worked well, yielding a sampling error of only
  5.3 for the 1.2 million acres of Kenai area
  forest under study.
• 41 of all spruce alive in 1992 were dead in
  1998.
• 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 judged to
  have health at risk. 56 were in good health.
• About 25 of the residual spruce were 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
  or moderately risky tree health.
• The paper birch was found to have almost four
  times as much basal area in the at risk tree
  health class as the spruce.
• The primary vectors of Risk for the paper birch
  were conks on the roots or lower boles and crown
  dieback exceeding 33 of the crown.
• About 2/3rds of the birch regeneration exhibited
  heavy moose browsing in 1998.

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Result Natural regeneration findings

• Regeneration of the spruce was marginal, from 130
  to 400 trees per acre, but nearly absent in some
  areas due to grass invasion and competition.
• Regeneration of birch was quite good, in many
  places over 1000 trees per acre. However, as
  noted before, 67 of the 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 Alaska
  during the 1990s provided plethora of unique
  ecological information on forest dynamics and
  vegetative succession, some of which we were
  fortunate to capture in these studies.
• There is certainly even more information to be
  mined from this event in various other
  disciplines of nature and sociology.

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A Closing Thought to Remember

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