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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Bioassessment I
Influence of spatial factors on linkages among watershed landcover, environmental conditions, and macroinvertebrate assemblages in coastal-plain streams
R.S. King1, M.E. Baker1, M. Hurd2, P.F. Kazyak2, D.F. Whigham1, and D.E. Weller1. 1Smithsonian Environmental Research Center, Box 28, Edgewater, MD 21037, 2Maryland Department of Natural Resources, Annapolis, MD 21401
Developed and agricultural landcover are widely used as indicators of biological condition in streams. However, causal linkages between landcover and stream variables are often equivocal, particularly in low-gradient watersheds. We used a spatially explicit, multivariate approach to estimate the independent effect of catchment-scale landcover on water quality, habitat, and macroinvertebrate-assemblage composition in streams of the Maryland coastal plain. We used data collected by the Maryland Biological Stream Survey (MBSS) in 1995-97. After controlling for spatial proximity among sampling stations (spatial autocorrelation), we detected linkages between the proportion of developed landcover and stream acidity, conductivity, hydrology, substrate quality, and riparian condition. Several of these development-influenced factors were linked to macroinvertebrate assemblage composition. However, agricultural landcover was only linked to nitrate. The lack of a statistical linkage between agricultural landcover and most stream variables was partially due to a high degree of spatial contagion in agricultural landuse in this ecoregion, but preliminary results using distance-weighting of landcover also suggested that topography, riparian buffers, and spatial arrangement of agriculture may have been important factors that modulated its catchment-scale effect on stream condition. This suggests that the influential scales and patterns of landcover in coastal-plain watersheds will differ by landcover classes and stream variables.
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