The Ecological Benefit Of Soil And Water Conservation Forest In West Of Shanxi Based On GIS

Study area is located in Caijiachuan Basin in jixian of Shanxi province In this paper, the Quick Bird image which is obtained in October 21,2003 is used for extracting Ianduse of study area.. Representative standard plots with different density in 4 different Plant types of plantations are selected In the experimental area to make comparison and survey of tree growth characteristics including herb's biological diversity, water holding capacity of litter, soil physical properties, runoff and sediment yield in rainfall Stand and other factors which affects ecological benefits of soil and water conservation forest. We use SPSS to conduct level of analysis and principal factor analysis to the parameters and educe the Weight of the of various factors in determining soil and water conservation forest eco-efficiency so that we can establish ecological benefits evaluation system of soil and water conservation forest, and we can come to the region's existing water and soil conservation forest ecological benefit distribution map by enducing the region's soil and water conservation forest ecological benefit evaluation model based on the study area (Caijiachuan Basin) of the measured data fitting and,then applying the to the study area.The density of stands with the same age has a significant effect on stand growth conditions. Compared With same type stand in the survey, as pure Robinia pseudacacia stand density is 1325 plant/ hm2, Chinese pine density is 1733 plant/hm2, the mixed forest of Platycladus orientalis and Robinia pseudoacacia density is 2089 plant/hm2, the stand growth conditions such as tree height, diameter, crown width, and plant biomass is the best one among the same kind stand..The same kind of stand has different density. Undergrowth's species and quantity is limited by changing microclimate (such as light conditions, the forest soil temperature, soil moisture and soil nutrients distribution). The diversity index and evenness index of herb under the forest tends to reduce gradually with the increase of stand density and the diversity of herb stand in low-density stand is obviously higher than the high one. When pure Robinia pseudacacia stand density is 1325 plant/hm2, Chinese pine density is 1733 plant/hm2, the mixed forest of Platycladus orientalis and Robinia pseudoacacia density is 2089 plant/hm2, the diversity of three kinds of herb within the stand is 2.26,1.88,3.11 and evenness index is 0.72,0.63,0.8 respectively,which has highest diversity index and the largest evenness index in investigated Chinese pine stand, Robinia pseudacacia stand and the mixed forest of Platycladus orientalis and Robinia pseudoacacia.differences of crown density undergrowth between different forest types are significant And the biodiversity changes of herbaceous plants under Chinese pine Forest, Robinia pseudacacia Forest and the mixed forest of Platycladus orientalis and Robinia pseudoacacia range within 2.89～3.11,2.01～ 2.26,1.66～1.88 respectively and evenness index range within 0.78-0.8,0.64～0.72,0.58～0.63 respectively. These can be seen that the diversity index and evenness index of the mixed forest of Platycladus orientalis and Robinia pseudoacacia are significantly higher than Chinese pine Forest and Robinia pseudacacia Forest.Compared with the broadleaf deciduous forests (such as Platycladus orientalis and Robinia pseudoacacia),the Litter reserves of the mixed forests of coniferous and broad-leaved and needleleaf deciduous forests (such as Chinese pine and Locust mixed forests and Chinese pine forests) is larger than the deciduous broad-leaved forests, and the undecomposed layer of litter in the Locust forests is the smallest, with over 29.89% reserves of the total, however the undecomposed layer of litter in the Chinese pine forests is the largest, with over 54.25% reserves of the total. The maximum water-holding percentage of litter layer in turn is as followings:Locust> Chinese pine and Locust mixed forest> Chinese pine> Robinia pseudoacacia, it respectively was 213.47%,172.78%,147.91%,135.76%, indicating the water holding ability of the litter in the broadleaf deciduous forests is better than in the needleleaf deciduous forests.non-capillary porosity of Locust forests soil, the surface(0～20cm) amounts to 9.77%～10.56%,soil layer (20-40cm) amounts to 6.16%～8.02%, soil layer (40-60cm) amounts to 5.5%～7.14%,but non-capillary porosity of pure Chinese pine forests soil(0-20cm,20-40cm,40-60cm) is 8.81%～10.43%,5.84%～7.94%,3.05%-6.25% respectively, non-capillary porosity of Platycladus orientalis and Robinia pseudoacacia mixed forests soil(0-20cm,20～40cm,40～60cm) is 4.85%～7.08%,4.05%～6.12%,4.25%～5.15% respectively; and soil saturated hydraulic conductivity of each forest and stand respectively amounts to 7.6ml/10s for Locust forests,8.4 ml/10s for pine forests,6.91 ml/10s for pine and Robinia pseudoacacia mixed forests, indicating non-capillary porosity of Locust forests in layers of soil is largest compared with pine forests and Platycladus orientalis and Robinia pseudoacacia mixed forests in the investigation.Under the same rainfall circumstance, the condition of runoff yield and sediment production under all kinds of stand are quite different, and In the same rainfall circumstance, the runoff yield and sediment production in the forest all showed changes as follows:lawn> pine forests> Locust forests >the mixed forests, rainfall interceptive rates for the Locust forests remained at 17.27%-20.66%, and erosion modulus was 35.2,8.2,7.6,3.0 respectively. Mixed forests where runoff yield and sediment production is smallest has the best effect for rainfall conservation.