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F o r e s t L a n d s c a p e E c o l o g y L a b
Dr. David J. Mladenoff
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Modeling Insect Defoliation Outbreaks and their Effects on Carbon Dynamics of Forested Landscapes Contact Jane Foster |
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Background:
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Eruptive forest Lepidoptera defoliate millions
of hectares annually in North America, suppressing growth and weakening or
killing host trees, altering nutrient dynamics and affecting competition
among forest species. These defoliation outbreaks are recurring,
large-scale disturbances that influence the productivity and composition
of temperate forests over long time-scales. The objective of our research
is to model the long-term effects of periodic defoliation outbreaks on
above-ground Carbon dynamics and forest succession at the landscape
scale. In pursuing this goal, we seek to explain the relative importance
of certain biological interactions between defoliators and their hosts on
outbreak dynamics, as well as interactions between different defoliators
in the same landscape, and the role these interactions may play in
landscape Carbon cycling. |
Research question: |
In general, we want to understand how outbreak
defoliation events and cycles affect and possibly alter above-ground
Carbon dynamics over both short (1-5 years), and long (10-100’s years)
time periods. In particular, we are interested in how defoliation cycles
of different species of defoliators, some introduced some native, some
generalists and others specialists, may interact in the same forest
landscapes to compound defoliation effects on biomass, succession, and
forest composition. |
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Approach: |
We are focusing on the dynamics of defoliation events
and their cycles for three species of forest Lepidoptera: Forest
Tent Caterpillar (Malacosoma disstria Hbn.) (FTC), a native
generalist defoliator of deciduous species; Jack Pine Budworm (Choristoneura
pinus pinus Freeman) (JPBW), a native defoliator primarily of jack
pine (Pinus banksiana Lamb); and European Gypsy Moth (Lymantria
dispar L.) (GM), an introduced generalist defoliator. Our approach to
better understand the factors driving defoliation intensity during
individual outbreaks is to integrate field data measuring forest
composition and condition with satellite image data and derived products,
such as maps of defoliation intensity, using GIS and statistical
analyses. We will also map and quantify the spatial variability in
leaf-out phenology in our study areas using MODIS satellite data to better
understand the spatial variability in defoliation drivers (foliage age).
We will measure the severity (suppressed growth and mortality) of
individual outbreak events through a combination of historical satellite
image analysis and dendrochronological analysis from forest plots.
Finally, we will apply our findings about individual defoliation events to
develop a module for the spatially dynamic forest succession and
disturbance model, LANDIS II. We will simulate a variety of scenarios
involving multiple defoliators in two different landscapes to assess the
long term Carbon dynamics and trends associated with cyclical defoliation
disturbances. |
Results to date: |
Preliminary analysis of satellite derived defoliation
maps for a gypsy moth outbreak in western Maryland has yielded interesting
results. We see differences in defoliation intensity among some forest
communities that appear to relate to phenological differences. We are
also finding different relationships between forest composition and
defoliation intensity from the first year of the outbreak to the second.
The results from this analysis will help guide the development of a
biomass-defoliation module for the LANDIS-II model, which is currently
underway. |
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Figure 1: Satellite derived forest vegetation map (left) and
defoliation intensity map (right) for |
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Investigators: |
Phil Townsend, Rob Scheller, David Mladenoff, UW-Madison. |
Funding: |
NASA |
