A Cases Study Of Using Avian Community Characteristic Parameters To Assess The Effectiveness Of Subtropical Urban River Eco-restoration

In this article, The Qinghu site of Guanlan River in Shenzhen, the experimental reach, was selected as the study subject. The ecological restoration project of the experimental reach started in September 28, 2007, including ecological revetment works, riverbed restoration project, flood protection works, artificial wetland along the river, water quality improvement works and manual scavenging. However, water quality was the only indicator of this project's effect, which did not consider other components of river ecosystem, to say nothing of biological components.Birds, the top consumers of river ecosystem, play a pivotal role in maintaining energy flow and the maintenance of stability in the river ecosystem. The changes of bird richness and abundance can reflect the changes of the river habitats, and different birds like different river habitats. Therefore, the higher the river habitat heterogeneity is, the higher bird diversity index is. For this reason, this study attempts to assess the effects of river ecological restoration and points out the deficiency of the river ecological restoration design works according to the bird abundance, richness and diversity index in different habitats, which can supply references for the future design of river ecological restoration in cities.The bird surveys were conducted in November, 2009 and 2010 in different habitats of the experimental sites, and the survey results showed:(1) The habitat types can be mainly divided into river course (including riffle and step-fool), ecological revetment (including ecological bag revetment, stone cage revetment, riprap revetment and natural revetment) and artificial wetland, and made assessments for different habitats. The assessment results showed: The score of the river course habitat was low, so the bird species and numbers in this habitat should be lower; The score of the ecological bag revetment and the natural revetment was higher than that of the stone cage revetment and the riprap revetment, so the bird species and numbers in ecological bag revetment habitat and natural revetment habitat should be more than other two habitats; the wetland was fully artificial vegetation community that was not suitable assessment using multi-factor.(2) The two survey results showed that the ecotype of birds was mainly local resident birds in experimental sites, and different birds preferred different habitats. The species and numbers of the resident birds were increasing after the ecological restoration by year and year, and that showed the ecosystem of the experiment reach was gradually getting well.(3) It was shown that bird abundance, richness and diversity index of ecological revetment were higher than that of river course and artificial wetland, and the three indicators value was also growing year by year. This showed that the ecological restoration effect of ecological revetment was most conducive to perch for birds and the habitat heterogeneity and its quality were improving too.(4) River course: The alternating structure of riffle and step-fool which was interfered by seasonal floods, effluent purified by Longhua sewage treatment plant and artificial wetland, so the location, area of riffle and vegetation species had occurred changes. The bird richness, abundance and diversity reduced in 2010, and there were no birds in step-fool. Therefore, the restoration of the alternating structure of riffle and step-fool did not reach the design effect.(5) Ecological revetment: the bird abundance, richness and diversity of natural revetment and ecological bag revetment were higher than that of riprap revetment and stone cage revetment that showed natural revetment and ecological bag revetment were more conducive to perch for birds. Therefore, the restoration effect of this two revetment types were better.(6) Artificial wetland: the bird abundance, richness and diversity in 2010 had increased than in 2009. However, considering 40,000 m3 of wetland area, the bird species and total numbers were still too small, and no waterfowl perched in this habitat. According to the results of this study, the river restoration projects in future should take account of the following suggestions: The alternating structure of riffle and step-fool should prevent to be destroyed by floods, and a certain density of artificial roosting should be placed in step-fool; The trees, shrubs, vines and grasses that the birds like nesting, gathering, feeding and perching should be planted in the riparian zone. So, we must take natural revetment and ecological bag revetment except the area was easily eroded heavily by floods where should take riprap revetment and stone cage revetment; The trees should be planted sparsely, the fish be cultured, a certain water surface be maintained, the artificial wetland be maintained, different types of aquatic plants be planted, these ways in artificial wetland can increase vegetation diversity, provide perching conditions, and increase the Qing River Lake Mission Hills section of bird species diversity.