A GEOSPATIAL ASSESSMENT OF MOUNTAIN PINE BEETLE INFESTATIONS AND THEIR EFFECT ON FOREST HEALTH IN OKANOGAN-WENATCHEE NATIONAL FOREST

摘要

Fire-suppression over the past century has led to increased forest density and fuel accumulation. Increased stand densities and warm dry summers in the past few decades have predisposed dry, high elevation forest types to mountain pine beetle (MPB) outbreaks. MPB outbreaks occur in three successive stages-- the green (initial attack), red (visible attack), and gray (dead) stages. With the use of geospatial technology, these outbreaks can be better mapped and assessed to evaluate forest health. Field work on seventeen randomly selected sites was conducted using the point-centered quarter method. The stratified random sampling technique ensured that the sampled trees were representative of all classifications present. Additional measurements taken were soil nutrient concentrations (sodium [Na~(+)], nitrate [NO_(3)~(-)], and potassium [K~(+)]), soil pH, and tree temperatures. Finally, satellite imagery was used to define infestation levels and geophysical parameters--such as land cover, vegetation classification, and vegetation stress. ASTER images were used with the Ratio Vegetation Index (RVI) to explore the differences in vegetation, while MODIS images were used to analyze the Disturbance Index (DI). Four other vegetation indices from Landsat TM5 were used to distinguish the green, red and gray phases. Selected imagery from the Hyperion sensor was used to run a minimum distance supervised classification in ENVI, testing the ability of Hyperion imagery to detect the green phase. The National Agricultural Imagery Program (NAIP) archive was used to generate accurate maps of beetle-infested regions.