| The species, area and spatial distribution of vegetation in recent5years in Shanxi Yongdinghe watershed and its effect on soil erosion and soil physicochemical properties were studied by remote sensing data extraction, vegetation map collection and located monitoring. Further, evapotranspiration water consumption, soil water requirement and vegetation coefficients of different vegetation were analyzed, eco-water requirement per area and eco-water requirement amount in study area were studied basing on field investigation combined with GIS technology. The results showed:1. By the end of2008, the vegetation area increased961.87km2, increased by20.1%, forest,shrub and grass area increased to2326.74km2,3103.07km2and327.34km2, respectively. Compared with2004, forest, shrub and grass area increased100.65km2,790.28km2and70.93km2, increased by4.5%,34.2%and27.7%, respectively. The area of vegetation coverage degree<30%was8474.23km2, being43.11%of the total region area; that of30to45%was8474.23km2, being16.52%of the total region area; that of45to60%was4900.05km2, being24.93%of the total region area; that of60to75%was1904.75km2, being9.69%of the total region area; that of>75%area was1130.14km2, being5.75%of the total region area.2. The analysis of the dominant tree species and their distribution showed that the dominant forest species were Populus, Pinus tabulaeform and Larix gmelinii, the total area of these three species was63.5%of forest area; The dominant shrub species was Caraganaits and its area increased to218221.8hm2, being70.3%of the total shrubs area by2008.3. Soil erosion area in project region was6980.73km2, being35.51%of the total region area. Areas of each grade soil erosion were as following:Micro erosion area was12676.04km2, being64.49%of the total region area;light erosion area was3477.40km2, being17.69%of the total region area; moderate erosion area was3282.21km2, being16.70%of the total region area; strong erosion area was221.12km2, being1.12%of the total region area. From the end of1990’s to2009, soil erosion area has been reduced1604.58km2, reduced by18.69%. Compared with the end of1990’s, soil erosion intensity was also significantly reduced. 4. Based on the runoff plots located in Yanggao County, Shanxi Province, effects of different vegetation on soil and water conservation and soil moisture in Loess hilly area region were investigated. The results showed, compared with bare land, Caragana, Hippophae and Pinus tabulaeform could control soil and water losses effectively, with the runoff reduction rate of84.8%～95.9%and sediment reduction rate of95.2%～99.7%; wasteland and Alfalfa could control soil and water losses effectively from the third and fourth years, with the runoff reduction rate of82.8%and91.2%, and the sediment reduction rate of97.0%and98.0%respectively in the fourth years; Coefficients of variation(CV) of soil moisture were ranged from7.0～19.1%in different vegetation plots from April to September, and that of Pinus tabulaeform plot was the highest, Hippophae, Alfalfa and Caragana were following, and wasteland and bare land were lower; deficiency rates of soil water were ranged from23.98%-52.66%, that were in the order Caragana> Alfalfa> Pinus tabulaeform> Hippophae>wasteland> bare land, implying vegetation could increase the variation and deficiency of soil moisture.5. Effect of vegetation on soil physical and chemical properties in Loess hilly area region showed:Soil bulk density with vegetation cover were1.21-1.24g/cm3, that of bareland was1.28g/cm3, and that of wasteland reached to1.44g/cm3. Soil bulk density in bareland was significantly greater than in the vegetation plot. Soil porosity of different plot is45.7%-54.2%, tending to that in vegetation plot being lower than that of bareland and wasteland plot. Soil organic matter, total nitrogen and available nitrogen were also been affected significantly.6. Soil erosion modulus in wasteland in rocky mountain area ranged from7.28t/km2to275.02t/km2, with an average of100.25t/km2; Alfalfa, Pinus tabulaeform, Juniperus communis, Caragana korshinskii and Sabina chinensis all decreased the soil erosion modulus.7.The minimum eco-water requirement in Yongdinghe watershed in Shanxi Province was1628.495×106m3, the corresponding surplus was653.526×106m3, the suitable eco-water requirement was2709.477×106m3and the corresponding scarcity the minimal water requirement was427.457×106m3. The five counties with highest eco-water requirement were Yanggao, Hunyuan, Tianzhen, Datong, Zuoyun, their minimum eco-water were21O.21×1O6169.19×106158.83×106138.53×106128.13×106m3,that were12.9%10.4%9.8%8.5%7.9%of the total eco-water requirement in Yongdinghe watershed in Shanxi Province, respectively. Compared with minimum eco-water requirement, the counties with highest eco-water surplus amount were Yanggao, Shuocheng zone, Hunyuan, Tianzhen, Zuoyun, their minimal eco-water surplus were110.17×106,73.39×106,72.52×106,69.53×106,45.46×106, respectively. From eco-water requirement distribution from April to October, eco-water requirement were rather more from May to August, the4months eco-water requirement was65.2%of the total water requirement of vegetation growth period; followed by April and September, being24.9%of the total water requirement of vegetation growth period; and eco-water requirement was least in October, being9.9%. |
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