Tuesday, August 7, 2007 - 8:20 AMCOS 20-2: Distributions of amphibian assemblages of zero-order basins and their relationships to the landscape mosaic in the Mill Creek Watershed, Del Norte County, California
Hartwell H. Welsh and Garth R. Hodgson. USDA Forest Service, Pacific Southwest Research station
Headwaters amphibians have excellent potential to be used as biological indicators of ecosystem status because of their high site fidelity, sensitivity to disturbance, long lives, and ease of sampling. Furthermore, they offer large cost savings compared with sampling other vertebrates. Amphibians occur in large numbers in healthy forest ecosystems and play an important role in regulating invertebrate communities. In 2006 we conducted time-constrained upland searches, and aquatic area-constrained searches at 28 zero order sites in four forest seral stages of redwood forest on the Mill Creek property and adjacent parklands. Results showed significant differences in species numbers and assemblage composition between the stands on the heavily harvested Mill Creek property and those on adjacent late-seral parklands. For example, in the upland, we averaged 5.5 animals per hour on the property versus 12.7 animals per hour in the parkland. We suggest that as the managed forests on the property recover, amphibian numbers will approach that of the adjacent late-seral forest. We intend to compare these baseline values with future monitoring of these assemblages over decades in order to track changes in the Mill Creek biota as these forests recover.