| Sanhe wetland locates in east region of Guanzhong Plain in Shaanxi province, which is 68260hm2. It is a typical riverine wetland which is composed of riverbed and flood plain of Yellow River, Weihe River and Luohe River. During the historical period, swinging of the Yellow River controlled the formation and the development of Sanhe wetland; the influence of the human activity was relatively small. But in recent years with the development of peripheral economy, the influence of the human activity becomes more and more remarkable. The ecosystem and the function of Sanhe wetland degenerated obviously. So the study and protection of Sanhe wetland are very important to the construction of the ecological environment of Shaanxi province.Based on materials collection open-air on-site inspection and sample tests, the types of Sanhe wetland were divided and the different evolution modes were analyzed. On this basis, the ecological service function, ecological protective function and resource function of Sanhe wetland were appraised. Furthermore, the ecological situation of five kinds of wetland were compared and appraised. According to these analyses, the suggestions and countermeasures of protection and rational utilization of wetland resources were put forward.The main contents of the research include:1 The Main Kinds of Sanhe Wetland. Due to the differences of essential features of the key elements such as geomorphologic, hydrology , vegetation , soil and living beings, Sanhe wetland was divided into three levels: systems, types and kinds. The kinds including river body, reed wetland , meadow wetland, river silt wetland, saline wetland , ditch , fishpond , lotus pool and paddy wetland. The main characteristics and distributions of these kinds were analyzed.2 Evolution Modes of Sanhe Wetland. Under the natural state, moisture and salt determine the distribution and evolution of plant community in wetland. The distribution of plant community of Sanhe wetland is banded from centre of the river to bank. Influenced by human's activity, structure and function of wetland have been changed. Projects' building, agriculture's utilization and the pollution of wetland are the main factors influencing the evolution mode of Sanhe wetland. Riverbed's waterbecomes little by little and the range of wetland becomes atrophy because of the reservoirs' building of Yellow River basin and the climate aridity. The wetland losing water degraded to dry land or sandlot. Dams not only prevent the overflow of flood, but also turn the perennial wetland outside the dams into the seasonal wetland, which depends on the supply of precipitation. The species and quantities of the living beings were reduced because of the pollution and human's hunting. The agriculture's utilization and people's drain for reclamation turned wetland into dry land and saline wetland. Planting paddy and drawing water to irrigate in certain area caused ground water rising. Affected by strong evaporation, the salinization of wetland is being developed constantly.3 The Ecological Appraisal of Sanhe Wetland. The ecological appraisal includes ecological service function, ecological protective function and resource function of Sanhe wetland. Thirteen indexes that were chosen had been calculated by APH and the result is reflected by CEI. The CEI of Sanhe wetland is 0.681, less than 0.7, which indicates that the ecological quality of Sanhe wetland is ordinary. On this basis, five main kinds of wetland were chosen and appraised. The maximum CEI is 0.75 gained by reed wetland; secondly is 0.64, gained by water body. The CEI of river silt wetland, paddy wetland and fishpond are less than 0.5. That shows the wetland under the natural state has irreplaceable ecological effect and value. So the protection of the wetland should be put in primary position.4 Based on the summaries of evolution modes and analyses of ecological appraisal, the suggestions and countermeasures of the protection and sustainable utilization of Sanhe wetland were put forward.
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