Study On The Change And Its’ Impact Factors Of Wetland Bird In East Dongting Lake After The Operation Of The Three Gorges Dam

Wetland bird, an important component part in the wetland ecosystem, plays a vital role in maintaining ecological system stability and is a good indicator of environmental change in the wetland ecosystem. Birds are amongst the most iconic of ecological assets and high in the food chain and very sensitive to changes of the surrounding habitat. Unlike other species, wetland birds take many factors, such as food, water, space and the distance to residents, into consideration when choosing habitats. Both natural factors and human factors affect the distribution and richness of wetland birds, so sometimes we should consider the comprehensive effect while studying species-environment relationship. Bird habitat restoration is one of the important tasks in wetland restoration. Therefore, it is vital to study the adaptability of wetland restoration, evolutionary changes of birds in East Dongting Lake Wetland, effective management of East Dongting Lake Wetland, and to develop Wetland restoration technologies under the condition of river-lake relation change. Then, it would provide theoretical guidance for protecting the species diversity, the restoration of the habitat and sustainable utilization in East Dongting Lake.In this study, firstly, the changes of the bird community structure, quantity, and biodiversity were studied after the operation of the Three Gorges Dam. Then, we mainly focused on the dominant winter waterfowl and Anatidae birds which account for about70%of the total population in East Dongting Lake, and then study the relationships between landscape structure, habitat index, human disturbance and species, respectively, which may provide useful data and necessary information for the repairing work of the bird habitat. The results indicated that distance to road, distance to residents, patch density, number of vegetaion types, water area, sedge area had significant effect on waterfowl distribution (P<0.05) with the impact intensity being sedge area (69.70%)> patch density (64.56%)> distance to residents (42.94%)> number of vegetaion types (42.94%)> water area (32.67%)> distance to road (20.63%). Effects of sedge area and patch density reached highly significant levels (P<0.01), which indicated that sedge area and patch density were the two major factors. However, as for Anatidae birds, the results seemed to be a little difference. In summary, landscape structure, habitat index and human disturbance were significantly associated with the bird species abundance while the individual effect of habitat-level variables was most evident. Among the seven chosen environmental variables, five critical ones markedly related to the Anatidae birds with patch density alone accounting for35.38%of the variation in the bird date, while water area individually explaining56.92%, reed area capturing48.69%, sedge area capturing61.94%, distance to residents capturing30.65%, respectively.Finally, in this study, the main environmental factors were determined by the previous chapters, and absolute dominant species including Anser fabalis and Anser erythropuswere choosed as the research objects. Based on Levenberg-Marquardt (LM) algorithm, a BP neural network with three layers was established, which well expressed the unknown but literally existed relationship between wetland bird species and environment factors. Then it was applied to the bird species prediction, and the results indicated that the trend of actual value and forecast value of Anser fabalis were in substantial agreement and the maximum, minimum and average errors were1.69%,0.10%,1.01%, respectively. While, as for Anser erythropus, the maximum, minimum and average errors were11.52%,0.03%,4.22%, respectively. It was shown that BP neural network had fairly good simulation accuracy and could be satisfactorily utilized to predict the number of the bird species in East Dongting Lake.