Effects of Insect Defoliation on Regional Carbon Dynamics of Forests

Research Issue

On an annual basis, insects severely defoliate more than 20 million acres of forested land in the conterminous United States, affecting a larger area and incurring higher economic costs than any other disturbance.  However, the long-term costs and ecosystem consequences of insect outbreaks on forest health and productivity are difficult to quantify at the regional scale because of the variety of pests involved, differences in forest types affected, and varying spatial scale and intensity of the impacts.  In particular, the effect of insect activity on carbon cycling and sequestration at the annual and decadal scale is poorly characterized.   

Our Research

We propose the development of a multi-scale approach to monitor defoliation and its impacts on forest carbon cycling using MODIS, Landsat (or similar), and high-resolution imagery.  Our overall objective is to quantify productivity and carbon sequestration effects of insect activity in two representative regions of North America (Mid-Atlantic Highlands and Upper Midwest/adjacent Canada) at the scale of MODIS products.  Our analyses will provide estimates of defoliation extent and intensity, as measured through seasonal losses in leaf biomass and changes to forest productivity derived from Terra MODIS imagery.  The research is premised on the identification of characteristic trends in forest phenology associated with defoliation that can be applied across years to map defoliated areas and resulting declines in forest productivity.  Remotely sensed estimates of reduced forest production will then be used to drive LANDIS-II, a spatially explicit forest simulator capable of modeling insect impacts on forest biomass and successional dynamics.

Expected Outcomes

Our research will reduce the uncertainties present in assessing forest carbon sequestration under scenarios of insect perturbations and related feedbacks (e.g., harvesting and fire).  This will facilitate more accurate carbon accounting at the regional and potentially broader scales.  Through the use of simulation models, we will address potential future impacts under different forest management scenarios and differing assumptions about the spread and prevalence of damaging pests.  Through the use of MODIS, we propose a monitoring and measurement system that can potentially be adapted for temperate and northern forests worldwide, and will provide a tool to facilitate both forest management and policy decisions.

Research Results

McNeil, BE, de Beurs KM, Eshleman KN, Foster JR, Townsend PA. 2007. Maintenance of ecosystem nitrogen limitation by ephemeral forest disturbance: An assessment using MODIS, Hyperion, and Landsat ETM+ Geophysical Research Letters 34: L19406.

Research Participants 

Principal Investigators

• Philip A. Townsend, Department of Forest and Wildlife Ecology, University of Wisconsin - Madison
• Brian R. Sturtevant, US Forest Service- Northern Research Station Research Ecologist
• David J. Mladenoff, Department of Forest and Wildlife Ecology, University of Wisconsin - Madison

Research Partner

• Robert Scheller, Department of Environmental Sciences and Management, Portland State University 

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/forest_health/carbon_dynamics_insect_defoliation/