MAPPING INSECT DEFOLIATION USING MULTI-TEMPORAL LANDSAT DATA

摘要

Insect defoliation is a major natural disturbance to North America's forests, affecting large areas that result in considerable timber losses annually. To address this problem in Canada, a project has been initiated to develop and demonstrate multi-scale Earth Observation-based methods for mapping and monitoring the spatial location, extent and severity of insect defoliation events in a consistent and timely fashion. Reliable and standardized information on insect defoliation and other large-scale forest disturbances will support Canada's capability to meet national and international sustainable development, environmental health and carbon accounting reporting requirements. For this study, a Landsat multi-temporal change detection approach was developed for aspen and spruce budworm defoliation. Within-year spectral variation was mapped for aspen defoliated areas, capturing changes in severity and extent related to the defoliation/refoliation cycle. Multi-year/site analyses demonstrate the natural variability of onset, duration and severity of aspen defoliator infestations. Multi-year spectral variation was mapped for spruce budworm defoliated areas, showing an increase in area and severity of damage to coniferous regions over the duration of the infestation. Mapping results are promising and have shown consistency within and across sites in Alberta and Saskatchewan. Resulting vectors are in general agreement with provincial aerial survey vectors, but with increased spatial precision. Automation procedures have been developed to facilitate integration of the techniques into the National Environmental Disturbances Framework (NEDF). Ongoing work includes developing an approach to model severity of defoliation using ground measurements, adding new sites to increase the robustness of the geo-spatial techniques, and exploring alternate sources of imagery as a substitute to Landsat.