Influences of environmental factors on macroinvertebrate assemblages: differences between mountain and lowland ecoregions, Wei River, China.

Key environmental factors and the mechanisms of their influence on the physicochemical habitats and macroinvertebrate communities of streams may vary among ecoregions. We studied the differences in environmental (land use and physicochemical) factors and the mechanisms of their influence on macroinvertebrate assemblages between mountain and lowland ecoregions in central China. We applied generalized linear models to identify key environmental factors that influence macroinvertebrate metrics consisting of taxa richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, percentages of EPT and intolerant individuals, and the Shannon-Wiener diversity index. Environmental factors and macroinvertebrate metrics significantly differed between the ecoregions. Mountain streams had significantly lower nutrients and %silt, but had twice higher total taxa richness than lowland streams. Watershed land uses were key drivers that influenced the physical habitat in the mountain ecoregion and were the main drivers that influenced both physical and chemical conditions in the lowland ecoregion. Correspondingly, watershed scale land uses, as well as physical and chemical variables, explained more variance in macroinvertebrate metrics than local-scale land uses in both mountain and lowland ecoregions. The overall biological variation was explained better by watershed-scale than by reach-scale land uses, whereas the spatial scale over which land use and physicochemical variables influence streams varied across ecoregions. Our results suggest that better landscape planning should be adopted for watershed management to improve water quality and physical habitat, and thus the conservation and restoration of macroinvertebrate biodiversity.