Assessing changes in forest fragmentation following infestation using time series Landsat imagery

Abstract

The current epidemic of mountain pine beetle ( Dendroctonus ponderosae Hopkins) in British Columbia, Canada, has impacted an area of over 13 million hectares presenting a considerable challenge to provincial forest resource managers. Remote sensing technologies offer a highly effective tool to monitor this impact due to very large areas involved and its ability to detect dead and dying tree crowns. Conventionally, change detection procedures based upon spectral values have been applied; however, analysis of landscape pattern changes associated with long-time series change detection approaches present opportunities for the generation of unique and ecologically important information. This study is focussed on the detection and monitoring of the shape and area characteristics of lodgepole pine stands during mountain pine beetle infestation to quantify the progression of forest fragmentation and related loss of landscape connectivity. A set of landscape pattern indices were applied to a set of images consisting of six Landsat satellite images spanning the period from 1993 to 2006. Our results indicate that the impacts of the mountain pine beetle infestation on forest spatial pattern consist of an increase in the number of patches, an increase in forest patch shape complexity, a reduction in forest patch size, an increase in forest patch isolation, and a decrease in interspersion. These findings demonstrate the unique information available from long-time series satellite imagery combined with pattern analysis to better understand the combined effects of insect infestation and forest salvage and harvesting.