| This paper studied the variation characteristics of the soil quality in the Shenmu county, Hengshan county and Hequ county, then analysed the soil chemical properties, enzyme activity and mineralogy properties by field sampling and laboratory analysis. The results show the influence degree and mechanism of vegetation restoration on soil quality,1. the influence of vegetation restoration on soil chemical properties⑴The soil organic matter content have a great differece under the different vegetation restoration in the same area and the same vegetation restoration in the different area . Compared with farmland, Poplar land can enrich the soil organic matter content in Shenmu county farmland; In Hengshan county caragana land can enrich the soil organic matter content obviously; The three different vegetation restoration can enrich soil organic matter content in Hequ county, grassland(waste land) increased greatest among the three methods.⑵In the different vegetation restoration model, soil total nitrogen content increased greatest in caragana land in shenmu county. Soil total nitrogen content can increase in both poplar and caragana land in Hengshan country, moreover in Hequ county , which increased obviously in Poplar land. The caragana land can improved the Soil available N content in Shenmu and Hengshan county in great degree, however in Hequ county was poplar land.⑶Soil total phosphorus increased in different vegetation restoration models in Shenmu county; The soil total nitrogen content increased significantly in poplar land in Hengshan county and Hequ country. For soil avaliable phosphorus, poplar land and wasteland had great increase in Shenmu county; The soil avaliable phosphorus content hadn't increase in different vegetation restoration models, furthermore, decreased in poplar woodland in Hengshan county; and the soil avaliable phosphorus content increased greatly in caragana land in Henqu county.⑷The soil total potassium content increase greatly among in three methods, poplar woodland were first, wasteland and caragana land took in the second place. Same as in caragana land, the soil total potassium contend increased in poplar land In Hequ country, which were higher than waste land; In Hengshan country, the soil total potassium increased slightly in the waste land increased,but the soil total potassium was decreased In the poplar and caragana land. The soil avaliable potassium increase significantly in the caragana land in Shenmu country, the same as in Hengshan county. The soil avaliable potassium content increased significantly in Poplar land in Henqu country.2 the influence of vegetation restoration on soil mineral content During the vegetation restoration, the soil mineral content is SiO2> Al2O3> Fe2O3> TiO2> MgO. Different area had different influence on soil mineral content. All mineral content can increase greatly in Poplar woodland in Shenmu county; The content of SiO2,Fe2O3 and Al2O3 were increased in Arbor forest(poplar and willow) , but the content of TiO2 and MgO decreased in different vegetation restoration methods in Hengshan county. The content of TiO2 increased significantly in different vegetation restoration methods, especially in the waste land, but the content of Fe2O3 and Al2O3 decreased , content of SiO2 had a little increase, content of MgO showed a volatility. The soil molecular ratio showed a stable condition in Shengmu country in Hengshan county and Hequ county, which hadn't a obvious rule ,but iron and aluminium had a higher content in the lowest layer of soil profile.3 the influence of vegetation restoration on soil enzyme activity⑴Contrast with farmland, the invertase activity of orchard land was higherowed to the fertilizing and fine management; the invertase activity of caragana land was lower, but significangtly higher than poplar land and waste land in Shenmu country, The soil invertase activity was high in the three vegetation restoration methods, the order was poplar>waste land> caragana land>farmland in Hengshan country; The invertase activity were higher in the Robinia pseudoacacia land and waste land, but lower in the caragana land and poplar woodland than the farmland in Hequ country.⑵Contrast with farmland, the urinary enzyme had a higher activities in all vegetation types except waste land, and showed a little difference in Shenmu country; The urinary enzyme activities was caragana > willow > poplar in Hengshan country, and both poplar and willow lower than farmland; The urinary enzyme activities was orchard> Robinia pseudoacacia> caragana in Hequ country. The urinary enzyme activities of caragana was little more than farmland.⑶In the different areas, the activity of alkaline phosphatase in caragana is all higher than in farmland. In ShenMu county, the activity of alkaline phosphatase in caragana is highest, and the poplar plantation is lowest. In HengShan county, the activity of alkaline phosphatase in farmland is lower than any other vegetation,In which caragana was highest, Robinia pseudoacacia and poplar had no differece, waste land was lowest. In QuHe county, the order of the activity of alkaline phosphatase is poplar > orchard> waste land > locust > caragana> farmland。⑷The activity of catalase in poplar is decreasing than the control in ShenMu county. The activity of catalase in caragana is greatly higher than poplar and wasteland. In HengShan county, the order of activity of catalase is caragana > poplar > farmland > wasteland, and the activity of catalase in caragana is greatly higher than in poplar. In HeQu county, the activity of catalase changes fluctuatingly in different vegetation types, and reached the lowest in 20-40cm of the soil layer.
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