Soil Nutrients And Biological Activities Of Four Natural Shrub Communities In The Horqin Sandy Land

The objective of this study was to determine the effects of spatial positions and shrubs on soil nutrients and biological activities, with four communities{Caragana microphylla, Atrphaxis manashurica, Salix flavida, Artemisia halodendron) in western Horqin Sand Land. The characteristics for changes of the soil nutrient contents and biological activities among different sites (rhizosphere-RS, under shrubs-US and between shrubs-BS) and soil layers (0～10cm,10～20cm and20～30cm) were studied. The involved index includes the contents of soil organic matter, total nitrogen, available nitrogen, total phosphorus, available phosphorus, available potassium, and the activities of polyphenoloxidase, phosphomonoesterase, dehydrogenase, urease, protease, nitrate reductase and the functional diversities of soil microbe.The results showed that there were obvious special and community heterogeneities in distributions of soil nutrients and biological activities. The majority indexes in surface layer are higher than those in the other soil depths, RS>US>BS, and indexes in the A. manashurica are higher than that in the other communities, dehydrogenase activities in the S. flavida are highest.There was a significant relevance among six nutrient contents in the aeolian sandy soil; the activities of soil polyphenoloxidase, phosphomonoesterase, nitrate reductase, urease and protease were highest in the A. manashurica communities, and activity of soil dehydrogenase under the S. flavida communities was higher than those in the other communities; there was a significant relevance between phosphomonoesterase, urease, protease, dehydrogenase and nitrate reductase; polyphenoloxidase had significant relevance with protease, nitrate reductase and urease, however no relevance between it and dehydrogenase are observed. Soil in C. microphylla communities had the highest functional diversities of microbe, followed was A. manashurica communities.The utilization of31carbon sources on Biolog ECO plates of four communities were as follows:RS of C. microphylla>RS of A. manashurica>US of C. microphylla>US of A. manashurica>US of A. halodendron>US of S. flavida>RS of A. halodendron>BS of S. flavida> BS of C. microphylla>RS of S. flavida>BS of A. halodendron>BS of A. manashurica. With the factor analysis the4main factors which affected growth of shrub are: organic matter, total nitrogen, total phosphorus, nitrate reductase, phosphomonoesterase. The four communities have the typical "fertile island" effect, especially in the surface soil. Therefore, it should be paid more attention to natural shrub community restoration and conservation, to enrich soil nutrients effectively and provide the basic conditions for natural community recovery in the reconstruction process of degraded ecosystems of Horqin Sandy Land.