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This study of Ansai County in Loess Hilly Area Small Catchment Communities locust different site conditions, sea buckthorn community, Caragana community, Lespedeza bicolor community, Phragmites communis, wheatgrass community, tarragon community, sand play prosperous communities for community structure and soil moisture, nutrients, enzymes comprehensive research and analysis, main conclusions are as follows: (1) The Institute involved mainly in plant community composition dicots predominant, followed by monocots. Dicots mainly in Rosaceae, Asteraceae and Fabaceae, while monocots mainly in grass. Therefore Rosaceae, Asteraceae, Fabaceae and grasses in the area flora plays an important role. Locust communities which mainly consists Rosaceae and Compositae composition, sea buckthorn community, Caragana community, Lespedeza bicolor community, tarragon community, wheatgrass community, adsurgens community, mainly by Phragmites communis Asteraceae and Fabaceae plant composition. (2) In the locust communities, different slope evenness index, diversity index, dominance index difference reached a significant level (p lt; 0.05); in the three shrub, buckthorn community and davurica Lespedeza community richness index, evenness index were significantly different (p lt; 0.05), ecological dominance index showed Lespedeza bicolor community gt; buckthorn community gt; Caragana community, diversity index showed buckthorn community gt ; Caragana community gt; Lespedeza bicolor communities; communities in four kinds of herbs, reeds, adsurgens Community and tarragon community richness index, evenness index were significantly different (p lt; 0.05), Phragmites communis with wheatgrass evenness index were significantly different (p lt; 0.05), ecological dominance index showed tarragon community gt; wheatgrass community gt; milkvetch community gt; Phragmites communis. (3) soil moisture spatial variability of different plant communities as follows: the different site conditions locust communities in soil depth greater than 100cm, the soil moisture content is greater than the sunny slope communities Communities; greater than 120cm in soil depth, the soil moisture With the growth of the amount of the increase of forest age; three kinds of shrub in the 0-260cm soil depth, the big variations in soil moisture and sea buckthorn communities are lower than other communities in soil moisture; depth in the soil 0-140cm, the higher soil moisture Caragana community, while deep in the soil, soil moisture content community Lespedeza bicolor higher; several herbaceous communities in soil moisture content expressed as: Phragmites communis soil moisture content is relatively high, The tarragon community is relatively low soil moisture, soil depth is 150cm in less soil moisture adsurgens communities are lower than other communities. (4) based on the Loess Plateau soil nutrient content of different grading standards of Soil organic matter, total nitrogen, available nitrogen, potassium, available phosphorus Statistical analysis showed that these types of nutrients in the area at a low level. Locust communities in which only a depth of 0-10cm soil layer, the organic matter, total nitrogen, available potassium belong to a higher level, while the available nitrogen, available phosphorus and shrubs, herbaceous community of soil organic matter, total nitrogen, available nitrogen, potassium , available phosphorus concentrations are at a low level, and some even reached very low levels. And in the soil depth of 20cm or less, all communities potassium, available phosphorus content difference did not reach a significant level (p gt; 0.05). Different types of vegetation communities have a table of nutrient cohesive effect. And overall nutrient content as follows: arbors gt; shrubs gt; herb, but Lespedeza bicolor community not only lower than Caragana soil nutrient content, seabuckthorn community is also lower than reeds, adsurgens community. (5) the area communities of different vegetation types on soil enzymes in Table cohesive effect, and the overall performance of the activity as follows: arbors gt; shrubs, herbs. In locust communities can explain aspect, forest age is affecting soil urease, catalase activity factor, and slope affect the invertase activity factor, age is a factor affecting amylase activity. (6) communities in different vegetation types in the area of ??soil pH range is small, and alkaline, and with the increase of soil depth tended to increase the pH, and the pH value of different slope there was a significant difference (p lt ; 0.05). (7) Through correlation analysis between soil factors come in different vegetation communities, soil pH and enzyme activity showed different degrees of negative correlation (p lt; 0.05); soil organic matter and enzyme activity was a significant positive correlation (p lt; 0.05), which reached a correlation with alkaline phosphatase highly significant (p lt; 0.01); nitrogen and alkaline phosphatase activity also showed a significant positive correlation (p lt; 0.01), and the available nitrogen, nitrogen correlation with urease have reached a significant level (p lt; 0.05). (8) In the locust communities, soil moisture, soil nutrients, soil enzyme activities and evenness index, diversity index, ecological dominance index with the growth of black locust forest age increases. Communities in the bush, richness index, diversity index and soil nutrients, enzyme activity showed a consistent variation. In herbaceous plant communities, soil moisture, nutrient content, enzyme activity and community richness, diversity index, evenness index showed a consistent variation.
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