Study On Abandoned Farmland Vegetation Community Characteristics And Soil Erosion And None-Point Source Pollution At Water Catchment Region Of Middle Route For Soute-to-North Water Diversion Project

South-to-North Water Diversion Project is a huge project. This will influence billions Chinese people, so the environment protection and water safety insurance have very significant meaning for China. This paper aimed to vegetation restoration, soil erosion and none-point source pollution. Describe about the vegetation community features in different abandoned stage of abandoned farmland through fields investigation. Use Cluster Analysis and Polar Ordination classified the succession stages of different vegetation communication on abandoned farmland. First use "Silt Fences"monitor erosion sedimentation interiorly under different vegetation types and succession stage. Take pH, COD, NH4+-N,　NO3—-N and phosphate as main none-point source pollution features, use Correspondences Analyses study the none-point source pollution features under different vegetation cover and land use form. Furthermore, raise some suggestion for the waterhead region protection and ecological reparation of middle route South-to-North Water Diversion Project. The main conclusions are: (1) The results show that the process of herbaceous vegetation restoration can be divide into the following stages obviously: Capsella barsapostoris + Acalypha australis + Conyza canaclensis Community(1 year abandoned); Conyza canaclensis + Chenopodium glaucum Community(2 years abandoned); Artemisia argyi + Conyza canaclensis + Artemisia scoparia Community(3~6 years abandoned); Imperata cylindrical + Artemisia subdigitata + Artemisia lavandulaefolia + Setaria viridis Community(7~12+ years abandoned). Herbaceous community structure became more stable after 3 years abandoned and its herbaceous vegetation restored elementarily. (2) There have significant difference of erosion amount between different vegetation caver and succession stage. The maximal erosion occur on slope farmland, Castanea mollissima forest erosion amount higher than more than 5 years abandoned farmland and minimal erosion was in natural secondary forest. Compare the erosion amount with natural secondary forest, corn land was 156.9 times higher, potato land was 190.2 times higher, 1 year abandoned farmland was 58.8 times higher, 2 years abandoned farmland was 48.3 times higher, 5 years abandoned farmland was 10.6 times higher, 8~9 years abandoned farmland was 2.3 times higher, Castanea mollissima forest with clearance of grass was 19.5 times higher and Castanea mollissima forest without clearance was 12.8 times higher. (3) Natural secondary forest and more than 5 years abandoned land have the higher erosion resistant capability than Castanea mollissima forest. Farmland and abandoned farmland in the beginning stages have the worst erosion resistant capability. This is related to vegetation cover and human disturbance. (4) The runoff none-point source pollution have significant difference between all the studied 9 vegetation types besides 5 years abandoned farmland and 8~9 years abandoned farmland. pH show no significant difference under different vegetation cover and land use. NH4+-N　and　NO3—-N higher in Castanea mollissima forest but most phosphate and COD comes from farmland and abandoned farmland in the beginning stages. More than 5 years abandoned farmland and natural secondary forest have lower content of all the pollution features. (5) Abandoned farmland shows satisfied ecological effects. Erosion intensity decreased after abandoned and erosion resistant capability increasing during abandon lasting. Furthermore, none-point source pollution on abandoned farmland also decline after abandoned. (6) Clearances of grass under Castanea mollissima forest decrease erosion resistance capability of slope, meanwhile, enhance the none-point source pollution. The erosion amount in clearances of grass Castanea mollissima forest are 35% higher than no clearance. The content of NH4+-N,　NO3—-N and phosphate in Clearance plots are 4.02mg/L,4.59 mg/L and 0.11 mg/L, higher than no clearance 3.63 mg/L,4.01 mg/L and 0.08 mg/L. (7) Vegetation restoration is the most efficient approach for the Water catchment Region management of Middle Route South-to-North Water Diversion Project. Reduce the area of slope farmland as much as possible, Encourage and promote organic farming, reduce chemical fertilizer usage, promote forestation, these will be benefit for the soil erosion and none-point source pollution control. (8) "Silt fences"is a convenient, economical, and higher adaptability method to monitor slope soil erosion. This method can be applied on soil water erosion monitoring and erosion comparison between different slopes.