Date of Award:
Doctor of Philosophy (PhD)
Department name when degree awarded
Fisheries and Wildlife
Michael L. Wolfe
Natural disturbance events influence the patterns and processes in many forest ecosystems. Ecosystem management of coniferous forests in western North America requires the recognition of the importance that natural disturbance regimes have in achieving sustainable resource production and maintaining biological diversity . Mountain pine beetle epidemics have played an historic role in the succession and structure of lodgepole pine forests in this region. Their effects on wildlife habitat and communities are undocumented, but are presumed to be substantial. I sought to quantify these effects in forty 1-ha stands of monotypic, even-aged, mature lodgepole pine forest in northern Utah approximately 3-8 years following an extensive epidemic. I selected 5 stands that were unaffected by the epidemic and 35 that had tree mortalities ranging from 14 to 95 %. Mean understory biomass in 50 1-m2 plots demonstrated an exponential increase from 4g m-2 in unaffected stands, 40 g m-2 in stands with moderate (51-75% dead) tree mortalities, and up to 110 g m-2 in severely (76-100 % dead) affected stands. Plant species diversity and heterogeneity were highest in stands with moderate tree mortality. Horizontal visual obscurity (from 0- 2.5 m high) was highest in stands with> 40% tree mortality. Canopy cover and volume decreased linearly and curvilinearly, respectively, with increasing tree mortality. Foliage height diversity was higher in stands with moderate tree mortality than in stands with high, low, or no mortality. Abundance and diversity of avian species were highest in stands with moderate tree mortality. Small and medium-sized mammal species were more abundant and diverse in stands with moderate and severe tree mortality than in stands with no or low (26-50 % dead) tree mortality, but the pattern is less clear than for avian species. Fecal pellet groups of large ungulates increased linearly with increasing tree mortality, but the pattern of occurrence of snowshoe hare fecal pellets to increasing tree mortality was less clear. Insect abundance and species diversity increased linearly with tree mortality. Canonical correspondence analysis of insect, avian, and mammalian communities revealed that understory vegetation biomass, diversity, and heterogeneity, as well as foliage height diversity, were the habitat factors that consistently explained the distribution of these species in stands affected by beetle-caused tree mortality.
Stone, William E., "The Impact of a Mountain Pine Beetle Epidemic on Wildlife Habitat and Communities in Post-Epidemic Stands of a Lodgepole Pine Forest in Northern Utah" (1995). All Graduate Theses and Dissertations. 799.
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