| The objective of this research is to explore the community structure and function of aquatic beetles at different environmental factors and how the change of land use influences on benthic index of biotic integrity (B-IBI) in Xitiaoxi catchments, Zhejiang Province, China..12 families and 36 genera of aquatic beetles were collected from 38 sampling sites on May 2005. Stenelmis and Psephenoides are dominant genera with higher frequencies of occurrence(78.97% and 67.89%), but other 29 genera occur less than 15%. Canonical Correspondence Analysis (CCA) between aquatic beetles and environmental factors show that the canopy is the main factor affecting beetle community distribution. However, TP, water conductivity and habitant quality are also important. Sampling sites are classified into three groups through clustering analysis using 17 environmental factors. Aquatic beetle community in group 2 had the highest richness(26 taxa). Species composition in group 1 (18 taxa) and group 3 (16 taxa) are significantly different (p<0.01). Macronychus, Zaitzevia, Scirtes, Stenocolus, Berosus, Laccobius, Ectopria are mainly occur in clean water, but Hydrocassis and Ancyronyx only occur in heavy polluted water.Changes of land-use and land-cover strongly influence on stream ecosystems. In the present study we evaluate the effects of these changes on the biological condition of Upper Xitiaoxi watershed Zhejiang Province, China, using a benthic index of biotic integrity (B-IBI). Benthic macroinvertebrate assemblages were sampled from 62 sites in first- to fourth-order streams in 2004 to 2005 to develop a B-IBI. The land covers for each site was estimated at sub-basin riparian-zone and local scales using 2003 satellite image and a Digital Elevation Model. We showed that B-IBI was negatively correlated with the percentages of croplands, bamboo forest, and the residential area. The percentage of croplands was strongly and negatively correlated with B-IBI at all three spatial scales, sub-basin (r=-0.527, p<0.001), riparian (r=-0.665, p<0.001), and local scales (r = -0.696, p<0.001). The percentages of coniferous forests, broad-leaved forests, and blend forests were positively correlated with the B-IBI. The percentage of the broad-leaved forests was strongly correlated with B-IBI at the local (r=0.618, p<0.001) and riparian scales (r=0.589, p<0.001), and less so at the sub-basin scale (r= 0.333, p<0.001) However, the percentage of coniferous forests was significantly correlated only at the sub-basin scale (r=0.366, p<0.001). With croplands < 50% of the whole catachment, B-IBI declined linearly as the percentage of the cropland increased, however, the index leveled off when cropland reached 27% of the sub-basin, 57% of riparian zone, or 59% at the local scales. Furthermore, the linear correlation of the percentage of the cropland at local scale with B-IBI was the strongest (r=-0.808, p<0.001, n=46). Our results suggested that a buffer with higher percentage of forest land cover between stream watercourse and cropland should help to maintain or improve the biological conditions of Upper Xitiaoxi watershed.
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