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RELATIONSIPS BETWEEN AQUATIC INVERTEBRATE ASSEMBLAGES AND REACH AND LANDSCAPE ATTRIBUTES ON WADEABLE, WILLAMETTE VALLEY STREAMS IN AGRICULTURAL WATERSHEDS
Citation:
Gerth, W., A. T. Herlihy, P R. Kaufmann, J Van Sickle, T. J. Moser, P. J. WIGINGTON JR, AND J. Li. RELATIONSIPS BETWEEN AQUATIC INVERTEBRATE ASSEMBLAGES AND REACH AND LANDSCAPE ATTRIBUTES ON WADEABLE, WILLAMETTE VALLEY STREAMS IN AGRICULTURAL WATERSHEDS. Presented at Oregon American Fisheries Society/The Wildlife Society Joint Meeting, Portland, OR, February 14-16, 2001.
Description:
In summer 1997, we sampled reaches in 24 wadeable, Willamette Valley ecoregion streams draining agriculturally-infiuenced watersheds. Within these reaches, physical habitat, water chemistry, aquatic invertebrate and fish data and samples were collected. Low-level air photos were used to assess riparian and watershed land use. Aquatic invertebrate data were analyzed using non-metric multidimensional scaling (NMS) ordination. Correlations with the ordination identified the strongest relationships between aquatic invertebrate assemblages and stream attributes measured at reach, reach-riparian, riparian corridor and watershed scales. By limiting the study to one ecoregion, placing upper and lower limits on catchment sizes, and only sampling in streams with <6% catchment urban development, we reduced many of the confounding factors that often preclude regional surveys from adequately assessing the influence of agricultural land use alone. Invertebrate assemblage structure was correlated with agricultural land use in riparian corridors, but not with agricultural land use in reach-rip arian zones, nor with agricultural land use in whole watersheds. Invertebrate assemblages were also correlated with several variables measured in sampling reaches including physical habitat (%slow vs. fast water habitat, %hardpan clay vs. gravel/cobble substrates), water quality (conductivity, ANC, and concentrations of Ca2+, Mg2+, Na+, and CF), and fish-IBI scores.