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INFLUENCES OF LANDSCAPE CONTEXT, HYDROLOGY, AND NON-NATIVE SPECIES ON WETLAND FAUNAL COMMUNITIES: IMPLICATIONS FOR REGIONAL CONSERVATION AND MITIGATION PRACTICES
Impact/Purpose:
Wetlands constructed for mitigation are functionally different than natural wetlands, tipping the balance out of favor for native amphibians. This study evaluates the response of amphibian communities to hydrology, exotic predators, and landscape context in natural and managed wetlands in the Willamette Valley, Oregon.
Description:
The two main issues affecting wetland fauna appear to be spacial arrangement of wetlands and widespread changes in wetland hydrology at the landscape context. EPA-ORD and the USGS in Corvalis are conducting field surveys, laboratory trials, enclosure experiments, and spatially-explicit modelling to determine how biotic, abiotic and anthropogenic factors affect the distribution and persistence of native amphibians. Specific objectives are to: (1) document occurrence of pond amphibians, exotic fish, bullfrogs, crayfish and macroinvertebrates in relation to wetland, riparian, and landscape characteristics; (2) clarify mechanisms that determine formation of pond amphibian communities in the Pacific Northwest, and their relationship to wetland management and regulatory decisions; (3) determine how regional changes in land use and wetland management are likely to affect native amphibians in the Willamette Valley; and (4) develop recommendations for wetland management and land-use planning to benefit native amphibians and other wetland dependent fauna. The third field season of wetland surveys is underway in 2001. Over 60 wetlands representing a variety of wetland types and associated landscape variables have been surveyed for wetland fauna, abiotic factors, vegetation characteristics, and hydrology. Lab and field experiments have examined behavorial responses of nauran amphibians to predator presence, and comparative predation by introduced fish species on native amphibian larvae. Landscape analysis and population modeling are currently underway to predict future amphibian biodiversity at wetlands under different landscape use patterns . The final research report (summer 2002) will include recommendations for amphibian monitoring, classification and management of wetlands for suitable amphibian habitat, and identify further research needs .
