Abstract:

The stream of Xiangxi River system was divided into six orders based on 1〖DK1〗∶50 000 relief maps.A total of fiftythree sampling sites were sampled.The macroinvertebrate communities were divided into five main functional feeding groups,including predators (PR),shredders (SH),scrapers (SC),collectorgatherers (GC) and collectorfilterers (FC).The collectorgatherers and scrapers,which feed on benthic algae,riparian detritus and fine particulate organic matter from the stream bottom,were the main groups in Xiangxi River system.The density and biomass of different functional feeding groups changed in the different stream orders.The GC and FC increased with the rising of stream order,while the SH and SC decreased.The PR density was higher in the downstream and biomass was higher in the upstream.The trend showed that the autochthonous energy dominated in the upstream and the input of allochthonous energy dominated in the downstream.The relationship between density of functional feeding groups and environmental factors was analyzed.Results showed that FC was significantly correlated with the width of river and Ca2+.The GC and SiO2 were highly correlated.The relationship between the SC and the elation and ammonia was significant.And the relationship between the SH and the PO4P and conductivity was also important.

Key words: Xiangxi River system, stream order, macroinvertebrate in the stony habitat, functional feeding groups