Coupling Relationship Between Plant Community Structure And Soil Nutrient On Micro-topography In Loess Area Of North Shaanxi Province

The habitat differences of scarp, platform, shallow gully, collapse and gully have important influence on plant community structure on the slope of in loess area of north Shaanxi Province. Therefore, the different micro-topography categories were studied as the object in Hegou valley in Wuqi County of Shaanxi Province. Based on field observation and laboratory experiment, the response of plant community structure and soil nutrient to micro-topography was analyzed. What’s more, based on grey relational analysis, the interaction between Plant community structure and soil nutrient on different micro-topography. Results showed that the plant community structure could vary with interaction between plant community structure and soil nutrient. It provides important basis of vegetation restoration and soil quality improvement in Loess Hilly Region. The main research results were summarized as follows:(1) The species composition, coverage, herbaceous biomass, average height and vegetation diversity of plant communities on micro-topography were all better than those on undisturbed slope. Among them, the vegetation condition with shrub and tree seedlings of gully and collapse were the best, followed by platform and shallow gully, scarp was worst.(2) The mass fractions of soil organic matter, available nitrogen and available potassium in different micro-topography showed a significant difference (P<0.05), while the total nitrogen and available phosphorus were not significantly different. The soil nutrient content of gully and the collapse were significantly higher than other micro-topography, while scarp and undisturbed slope were the worst. The content of the soil nutrients on the soil profile showed obvious surface aggregation effect. The correlation relationships among the soil nutrients had different degrees, in addition, the relationship between soil organic matter and other nutrients were significant.(3) The soil organic matter and pH value were the most important factors that influencing plant community structure, and the Margalef index was the most important factors that influencing soil nutrient. The sort of relational degrees that between plant community structure and soil nutrient of different micro-topography were different. The soil organic matter and available nitrogen were the most important factors influencing plant community structure on scarp, gully and collapse. The soil organic matter and pH value were the most important factors that influencing plant community structure on shallow gully and platform. The pH value and available potassium were the most important factors that influencing plant community structure on undisturbed slope.(4) Based on gray correlation analysis, the indices of plant community structure and soil nutrient were founded in an evaluation model to evaluate the ecological restoration capability of micro-topography. The results were in the order of gully>platform>shallow gully>collapse>scarp>undisturbed slope. The ecological restoration index of gully, platform, shallow gully and collapse were greater than 0.500 and that these micro-topography were more favorable to the restoration of the ecological capacity of vegetation-soil ecosystem.