 |
Tuesday, May 19, 2009 - 11:45 AM
144
Understanding invertebrate responses to urbanization: The role of multilevel regression models
Thomas F. Cuffney1, Roxolana Kashuba2, Song Qian2, and Gerard McMahon1. (1) North Carolina Water Science Center, U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, NC 27607, (2) Nicholas School of the Environment, Duke University, Box 90328, Durham, NC 27708-0328
The effects of urbanization on macroinvertebrates were studied in nine metropolitan areas (Boston, MA; Raleigh, NC; Atlanta, GA; Birmingham, AL; Milwaukee-Green Bay, WI; Denver, CO; Dallas-Fort Worth, TX; Salt Lake City, UT; Portland, OR) as part of the U.S. Geological Survey’s National Water-Quality Assessment Program. Simple linear regression models relating invertebrate responses (e.g., Y = ordination site scores or metrics) to urbanization (e.g., X= multimetric urban intensity index, % developed land, or % imperviousness) showed statistically significant responses to urbanization in six of the nine metropolitan areas. Multiple regression models incorporating additional basin-scale land cover (e.g., forest, agricultural land) and environmental variables (e.g., temperature, precipitation) as predictor variables could not explain differences in responses among metropolitan areas. Multilevel models incorporating basin-scale (% developed land) and regional-scale predictors were able to explain differences in responses among metropolitan areas. These models demonstrated that regional-scale climate (temperature and precipitation) and land cover (antecedent agriculture) strongly affect invertebrate responses to urbanization. The non-significant regressions initially encountered in Milwaukee-Green Bay, Denver, and Dallas-Fort Worth resulted from the high levels of antecedent agriculture that obscured the effects of urbanization in these metropolitan areas and could not be detected using other regression models.
Web Page: urbanization, multilevel models, invertebrates