An Assessment of Wildlife Populations and Habitat in Herbicide-treated Jeffrey Pine Plantations

MASTERS THESIS: In the summers of 1977 and 1978 wildlife populations and habitat variables were sampled within young Jeffrey pine plantations in the 1960 Donner burn. Sites treated with 2,4,5-T six to seven years prior to sampling were compared with similar untreated sites within nearby plantations. Habitat variables showed the greatest variation between treated and untreated sites. On treated sites total live plant cover, evergreen foliage cover, and coniferous foliage cover were significantly lower than on untreated sites. No sinificant difference in small mammal abundance were detected although seven of nine species seemed to be favored by untreated habitat. Deer use appeared to be slightly greater on treated sites while snowshoe hare use was lower on treated sites. Avian populations appeared to be more sensative to the measured differences in habitat variables. The species identified as most indicative of treated habitat included the green-tailed towhee, Brewer sparrow, and calliope hummingbird. The indicator species on untreated plots included the dusky flycatcher, yellow warbler, and fox sparrow. This study sampled the entire variability of treated areas in proportion to their existence over the treated plantations, including sites heavily impacted and sites missed or only slightly affected by the spray. The habitat variables and animal populations were consequently more variable on treated than untreated sites. In contrast to a previous study of the area which sampled only one heavily treated site, this study found no severe impacts to wildlife or its habitat on the area as a whole six to seven years post-treatment. This raises a question on the effectiveness of the herbicide treatment in meeting management goals. It is not clear that pine growth was significantly enhanced.