| The loess plateau of china located at a transitional area where the semi-humid climate is changing into the semi-arid and arid climate. Because the evaporation is great more than rainfall, and the ground water is deep, soil water is always in the step of wane condition and the soil nutrient are also leanness and available nutrients are scantily, which makes the eco-environment of the plateau very fragile. Study on the issues of soil water's eco-environment and soil nutrient's background have very important signification to vegetation recovering in this area.Based on the achievement of related previous studies on this issue and the unsolved problems, here three aspects are concentrated in this dissertation for the issue. They are: Study on the Variation Law of Soil Water and soil nutrients' background and productivity of the Artificial Locust Woodland in northern shaanxi province;The characters of the communities restoration and soil properties change of different barren grassland in loess plateau.The objectives are approached both by field survey and lab analysis. The following results are obtained based on field data and analyses:1 .This paper showed the variation law of soil water content in eleven-year locust stands in different growth stages under different site types in Loess Plateau. There is lack of rainfall in experimental region. During its growth period, soil water content among different site types was: semi-shady >sunny > semi-sunny. Soil water content in three depths( 0 - 40cm, 40 -100cm, 100 - 220cm )was easily affected by the site type and the stage of growth. During its growth period, soil water condition couldn't be compensated except that of the depth of 0-40cm slightly raised again in terminal growth stage. Soil water content varies in different stages. The law was alike between initial stage and the peak of growth, but the rates reaching maximum of negative and positive were in the different soil depths, and the inflexions of increment and decrement by degrees were also different. The soil water content in terminal stage increased positively, and in surface reached the maximum, but decreased with the depths, except a little increment in the depth of 460 - 600cm.2.The contents of soil organic matter of 0-40cm is greater than other layers in eleven-year locust and 40-100cm are little low than 100-220cm. The contents of soil organic matter from 220cm are decreasing to end.The total N and available N is same disciplinarian as soil organic matter. Surface layer content is great than sub layer. Soil available P content is different from soil organic matter, total N and available N in eleven-year locust stands under different site types. The contents of available P are increasing along with depth increasing.The contents of soil available K have the similar trend under different site types, that is, the contents surface layer about 0-40cm is higher than sub layer. Under 40cm, the contents areabout 60mg/kg.3.Under the different site types, the contents of soil organic matter, total N, available N, P, K have no obviously difference. But the height of the Robinia pseudoacacia, the cap of the Robiniapseudoacacia, the diameter of the Robinia pseudoacacia above one meter of ground, the length of new branch have the similar disciplinarian: Semi-shady >sunny > semi-sunny no matter what May, July, September. We study the regular of soil water contents in 11 years Artificial Locust Woodland. The results showed that soil water contents are semi-shady >sunny > semi-sunny. So we can draw the conclusion that the reason of differential productivity of Artificial Locust Woodland in different site types is soil water content rather than soil nutrients. The growth condition of Artificial Locust Woodland has the consanguineous relativity between soil water content, which have been the key factor effected forest growth, so we must saw about the soil water eco-environment in different site types when arraying the forest and grass construction.4.In order to exploit the trend and rule of vegetation...
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