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MODELING STREAM MACROINVERTEBRATE COMMUNITY RESPONSE TO LAND COVER IN THE WILLAMETTE BASIN
Citation:
Herlihy, A. T. AND J. Li. MODELING STREAM MACROINVERTEBRATE COMMUNITY RESPONSE TO LAND COVER IN THE WILLAMETTE BASIN. Presented at Joint Meeting of American Fisheries Society and the Wildlife Society, Portland, OR, February 14-16, 2001.
Description:
We analyzed macroinvertebrate data from 104 stream sites in the Willamette basin to develop models of macroinvertebrate response to land use/land cover data that can be used to project future conditions under various alternative land use scenarios. We assessed macroinvertebrate response using both a RIVPACS model O/E score (observed taxa to expected reference site taxa ratio) and EPT (mayfly, stonefly, caddisfly) taxa richness (a commonly used assessment metric). Differences between the lOW gradient Valley streams and the high gradient mountain streams in the Willamette basin required running separate models in the two areas. In the Valley, O/E score was best predicted with a four variable multiple regression model that included % agriculture and % development in the stream network, longitude, and stream power (model r2=0.5 1). The EPT model included % agriculture and % development in the stream network, elevation, and stream power (model r2=0.63). In the upland, mountainous regions, we could not develop a good model relating macroinvertebrates to land cover. We applied the macroinvertebrate model to all second to fourth order stream segments in the Willamette basin using current land cover and site data. We also ran the model assuming a land cover thought to exist in the basin before Western settlement. Results showed a significant decline in current macroinvertebrate condition since Western settlement. These model results can also be applied to alternative future land use/land cover scenarios to study their effect on stream quality.