The Research Of Macrobenthos Communities Structure And The Relationship Of Breakdown For Leaves In Ashihe River

A comparative study of community characteristics of macrobenthos in different segments of the Ashihe River continuum in Heilongjiang Province through the 11 sampling points that were set up in upstream, midstream and downstream of the Ashihe River continuum in spring, summer, and autumn,2014. The relationship between community characteristics and environmental factors of macrobenthos had been analyzed according to the collecting macrozoobenthic, identification and determination of physical and chemical factors of river water respectively accomplished with the methods of dominance index(y), Margalef index (dM), Shannon-Wiener index and Canonical Correlation Analysis(CCA), etc. Also a leave disaggregate research on Sorbaria sorbifolia had been researched with the litterbag technique in three segments of the Ashihe River continuum. All these provided a theoretical basis for further research on the role that macrobenthos behavior in the water ecosystems.In this study 65 species macrobenthos were collected which belonged to 7 orders,26 families. And among of them, Diptera, Ephemeroptera, Tubificidae, Trichoptera and Plecoptera are the main dominant groups. Diptera species were most on the number, accounting for 49.2% of the total macrobenthos and ephemeroptera accounting for 21.5%. From the point of view of the whole drainage basin, the densities of macrobenthos were 103.99±45.50ind./m2,93.92±41.76ind./m2 and 74.66±5.10ind./m2 respectively in spring, summer, and autumn. Statistic analysis revealed that the maximus density was in spring, next in summer, the lowest in autumn; From the point of view of different segments of the river, the densities of macrobenthos were 116.54±96.51ind./m2,77.03±35.17ind./m2 and 84.72±42.35ind./m2 respectively represent the forest segment, farmland segment and urban segment, maximus density was in the forest segment, next in the urban segment, the lowest in the farmland segment. The dominant species of the macrozoobenthos in Ashihe River was one species of Sigara substriata, Ameletus montana, Limnodrilus helveticus and centroptilu sp.l.During the research,.the Shannon-Wiener index(H’) seasonal variation trend of macrobenthos in Ashihe River was summer (1.8)> autumn(1.68)>spring(1.1), the Margalef index (dM) seasonal variation trend was autumn(1.22)>summer (1.18)> spring(1.13). It showed that Shannon-Wiener index(H’) and Margalef index (dM) was the lowest in spring, because the low temperature of the water was not conducive to the survival of macrobenthos, resulting in lower macrobenthos diversity. The Shannon-Wiener index(H’) was significant different (P<0.05) in different segments of the Ashihe River continuum in spring and the value was 0.007 by analyzing the macrozoobenthie Shannon-Wiener index(H’) and Margalef index (dM) in different streams. The Shannon-Wiener index(H’) and Margalef index (dM) were significant different (P<0.05) in different segments of the Ashihe River continuum in summer, and the value were 0.031 and 0.006, respectively. The Shannon-Wiener index(H’) and Margalef indices (dM) were significant different (P<0.05) in different segments of the Ashihe River continuum in autumn, and the indices were 0.015 and 0.044, respectively.The Canonical Correspondence Analysis (CCA) result showed that:in spring, the mainly environmental factors that effects macrobenthos community structure were Total Phosphorus(TP) and Depth; in summer, the mainly environmental factors that effects macrobenthos community structure were Total Phosphorus(TP), Total Nitrogen(TN), Temperature, Redox potential and Depth; in autumn, the mainly environmental factors that effects macrobenthos community structure were Total Phosphorus(TP), Total Nitrogen(TN), Temperature, PH, Redox potential and flow rate.A period of 77 days research had been done on decomposition rate of Sorbaria sorbifolia leaves which been put in forest segments of upstream, farmland segment between upstream and midstream of the Ashihe River continuum and urban segment at the estuary which the Ashihe River flowed into the Songhua River. The result showed that the decomposition rate are all 0.02d-1 in forest segment, urban segment and farmland segment, all of them belonged to rapid decomposition group because of according with exponential breakdown model. The collectors/ gatherers played a major role in the process of leaves decomposition.