| The Loess Plateau is one of the most serious soil erosion regions in the world, where a large number of manpower and material resources have been poured into soil and water conservation management and research in the Loess Plateau, and make remarkable achievements. At present, how to use a unified standard to evaluate and analyze regional benefits of soil and water conservation has become a common issue for decision-makers and researchers. With the support of RS and GIS technology, this paper analyzed dynamic change of factors influencing benefits of soil and water conservation since the implementation of "The Soil and Water Conservation and Ecological Protection Projects of Yellow River in Tianshui City, Gansu Province ". This research applies ecosystem service function value methods to evaluation and analysis some benefits of soil and water conservation. The main conclusions are:(1) Establishing Parameters for benefit evaluation of region-scale soil and water conservation. Based on"national standard"and the principle of selecting indicators, applying ecosystem service function value method, and taking root in the loess plateau, this paper systematically analyzes the present research situation and problems of the benefits evaluation of soil and water conservation. And then, the paper suggested a regional-scale evaluation parameters system.(2) Establishing the factors database of Jihe Demonstration Zone which influences benefits of soil and water conservation. The database mainly consists of precipitation, runoff , vegetation cover, land use, topography map, DEM, soil, thematic maps, remote sensing image, field landscape pictures, and investigated data of practices of soil and water conservation.(3) Evaluating and analyzing the dynamic change of soil erosion. Based on the Ministry of Water Resources criteria for soil erosion, the erosion lever of Jihe Demonstration Zone mainly is moderate erosion. And the regional soil erosion decreased remarkably in 2005. Compared with 1997, the strength erosion, great strength erosion and violent erosion were reduced by 10%, 10% and 4% respectively.However, the evaluation based on the Regional Soil Erosion Model and the Chinese Soil Loss Equation showed that the soil erosion lever of Jihe Demonstration Zone mainly is micro and mildly erosion. Due to engineering practice factor, there is little variation of soil erosion based on Chinese Soil Loss Equation. Meanwhile, based on the Regional Soil Erosion Model, the soil erosion in 2005 was more intensive than it in 1997, due to the rainfall intensity. Although the vegetation covered much in 2005 than in 1997, the soil erosion caused by rainfall was far greater than the benefits of plants to reduce sediment, which led to more serious soil erosion in 2005 than in 1997. This result is opposite to the soil erosion evaluation of the Ministry of Water Resources. The reason is that the Ministry of Water Resources of soil erosion standard does not take the effect of rainfall on soil erosion into account.(4)Investigating scale changes of NDVI. In this paper, a method is proposed to get high spatial and temporal resolution NDVI products, by matching the histogram of ETM NDVI (30 m) to that of SPOT/VEGETATION NDVI product (1 km, one scene every month). The estimated NDVI products (30 m, one scene per month) are analyzed, based on several indicators such as statistical characteristics of image, histogram similarity and image fidelity. The results of this research can be applied to dynamic monitoring and prediction of the region-scale soil erosion.(5)Calculating the ecological value of different years in different state of soil and water conservation based on GIS with the date of climate, soil, topography and land use and obtained all the map of Jihe Demonstration Zone. This research chose one kind of ecological service respectively from hydrosphere, soil sphere, biology sphere and atmosphere to assess impacts of soil and water conservation on environment according to the progress of ecological service research. |
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