Ecological Risk Assessment For The Wetland Aside Xizang Railway

Xizang railway from Tanggula mountain to Lasa traverses wetland for 174 sections, and in totally for 65.489km. The small species population of animals and plants, little biomass, simple biological chain , slow circulation of substances and conversion of energy are all due to the bad environment, cold climate, drought, short period of growth. These factors ultimately bring to fragile environment and feebleness recovery.The ecological risk is the risk endured by the ecosystems and their all compositions. It indicates the effects to ecosystems and their compositions from uncertain accidents or disasters. All these effections may result in damnifing structures and functions of ecosystems. The ecological risk assessment for wetland emphasizes particularly on the harm that primary risk resourses(natural,man-made.etc) work to wtelands, in order to bring forward practicable solution.The population of Xizang region is small. The exploiture begins very late, and a majority of wenland systems are still in aboriginal states. The construction of Xizang railway brings a mass of human activities to the fragile alpine cold wetland systems, and inevitably accelerates the habitat fragmentation, and consequently leads to ruin of the habitats, decrease of species diversity, destruction of system configuration and the impact on species pervasion.Mainly considering the construction of Xizang railway as the man-make risk resourse, this paper assesses ecological risk to the wetland systems 50km alongside the Xizang railway, and advances relevant risk management to supply fundaments for environment managment of the Xizang railway.Ignoring those minor risk resourses with weak impacts , this article takes coast, snow disaster, drought and habitat framentation for the primary risk resourses. The wetland systems includes lake ecosystem, river ecosystem, meadow ecosystem, swamp ecosystem , bush ecosystem and cropland system. To analyse the landscape fragmentation index, landscape separation index, nature index and ecological losing index of six types wetlands, this item draws the conclusion that the respective ecological losing indexs of lake, swamp, meadow, river,bush and cropland ecosystem are 0.0156,0.0106,0.0021,0.0024,0.0034 and 0.0019. Different risk management measures are adopted in different wetland ecosystem. Digging earth and sewage discharge are avoided in a certain extent when the construction of railway is near those lakes. Occupancy swamps and cutting the earth's surface and underground runoff are prohibited near the swamps. Sewage discharge should be controlled strictly and water quality monitoring must be applied in every traversed rivers. The configuration of alpine cold swamp meadow ecosystem is very simple. The alpine cold swamp meadow is impressible by digging earth , so ecological recovery must be carried into execution while the construction is finished. Additionally, grazing should be conservative to reduce the degeneration.