Date of Award

Fall 12-1-1999

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Geography, Geology, and Anthropology

First Advisor

Marion T. Jackson

Abstract

This study utilized Landsat TM imagery to evaluate black-tailed deer habitat changes in a portion of the Mount Saint Helens blast zone in western Washington. The purpose of this study was to compare the post eruption vegetation changes with population trends for black tailed deer. The 55,000-acre study area comprises a Washington Department of Game Management unit (GMU 524) located to the northnorthwest of Mount St. Helens. Approximately 80% ofthe mostly forested study area was affected by lateral blast from the 1980 eruption. The area is predominantly private land managed for timber production but a small portion falls within the Mount St. Helens National Volcanic Monument. Black-tailed deer were abundant in the area prior to the eruption and populations increased in the years after the eruption. Populations have declined in recent years and researchers are concerned about the role that vegetative succession (specifically the increase in even-aged regenerating forests) may be playing in this decline. Four dates ofLandsat TM imagery (1984, 1988, 1991, and 1996) were classified to assess post-eruption vegetation changes in the study area. Vegetation classes were used to develop estimates of nutritional carrying capacity (NCC) for the study site on each image date. Carrying capacity estimates were compared to post eruption population trends for deer, the spatial distribution of forage and cover vegetation, and the density of open roads in the study site. Classified images were subset by elevation to examine patterns of change in summer and winter ranges for black-tailed deer. Overall classification accuracies were above 80% and remote sensing was useful in delineating general vegetation changes. Vegetation changes were most pronounced in the managed forests and lower elevations. Nutritional carrying capacity estimates did not correspond exactly with changes in demographic data for deer; however, the increase in closed canopy vegetation did associate more closely with a general decline in deer populations which has occurred since 1988. Analysis of data indicates that the increase in closed canopy vegetation reduced the usability of habitat by black-tailed deer; however, more extensive ground data are needed to determine the specific effects of closed canopy vegetation on habitat usability.

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