Responses Of Macroinvertebrates Community Characteristics To Local And Regional Factors In The Weihe River Mainstream And Typical Tributaries From The Northern Qinling Mountains

As the largest tributary of the Yellow River,the Weihe River plays an important role in promoting the economic development along the river and promoting the natural water cycle,which is responsible for transportation,water supply,power generation,climate regulation and other functions.The Qinling Mountains,the boundary between China's warm temperate zone and subtropical zone,are home to numerous streams and rich animal and plant resources,making them one of the key areas for global biodiversity conservation.However,in recent years,due to the rapid economic development and the interference of human activities,the mainstream of the Weihe River and its southern tributaries are facing problems such as the loss of water source function,the shortage of water resources and the aggravation of water pollution,which are in urgent need of protection and treatment.In order to provide a scientific basis for the protection and restoration of water ecology in the Weihe River Basin,macroinvertebrate in 40 river reaches of the Weihe River and typical tributaries from northern Qinling Mountains were investigated in October 2017 and May 2018 respectively.Based on field sampling and laboratory sample analysis,the background values of macroinvertebrates and water environment in the Weihe River mainstream and the Qinling drainage were investigated and analyzed.This study provides an in-depth understanding of the community characteristics of macroinvertebrates in the study area,clarifies the main environment driving factors affecting the community characteristics of macroinvertebrates,assesses the water quality of studied rivers and identifies the most significant local and regional factors that affect the taxonomic characteristics and functional feeding groups of macroinvertebrates under different human disturbance gradients.Its main conclusions are as follows:(1)A total of 210 species of benthos were collected and identified from 40 reaches in stduy rivers,belonging to 5 phonyms,8 classes,75 families and 189 genera.Aquatic insects were the most dominant group,accounting for 89.0%.The number of species and biomass in the five tributaries were higher than those in mainstream,which indicated that the ecological environment quality and the amount of biological resources in the southern tributaries of the Weihe River were better than those in mainstream.(2)Pearson correlation analysis and the multiple linear regression analysis showed that silt plus clay,conductivity and nitrate nitrogen had the most significant effects on the community characteristics of macroinvertebrates.According to the water quality evaluation results of the richness index and the BIological index(BI)method,27%and 20%of the mainstream of the Weihe River were better than lightly polluted(?),and 76%and 36%of the southern tributaries were clean(?)or cleanest(?),respectively.(3)With the decrease of human disturbance,the relative abundance of Coleoptera,Plecoptera,Arachnida,Scrapers and Shredders increased gradually in the three groups However,the relative abundance of Oligochaeta,Tubificidae,Hydropsychidae,Collector-gatherers and Collector-filterers decreased gradually in the three groups.Both the taxonomic composition and the composition of functional feeding traits were sensitive to human disturbances at different scales,but the latter was more responsive to specific human disturbances.