Spatial Variability Analysis Of Soil Trace Elements Under Different Land Use Types In The Small Watershed Of Southern Shaanxi

Land resource is an important resource for human survival, and rational use of land resources is of great significance to the improvement of agricultural production, ecological environment and human development. With the development of precision agriculture and the deepening understanding of trace elements, new challenges and higher requirements have been proposed for the study of specific variation of soil properties in space and its influencing factors. Therefore, the paper selects Hua Yan small watershed in southern Shaanxi as the study area, divide it into three zones:the upper reaches, the middle reaches and the lower reaches. The content rule of trace elements in different land use types were discussed about in each zone, by using classical statistics and geo statistics method, find the distribution rule of trace elements in space. The purpose of this study is to provide a scientific basis for the control of soil nutrient loss and rational use.Paper is divided into five parts. The first chapter is the introduction part, it puts forward the background and significance of the topic, combined with the existing related researches of domestic and abroad, determine the research content and technical route. The second chapter introduces the selection of study area and research methods of this paper, including research area, sampling methods, indoor experiment and treatment methods. The statistical methods used include the classical statistics method, the semi variance function analysis method and the spatial interpolation method.The third chapter and the fourth chapter is the main content of this research. First, using the geo statistics methods, analysis the trace elements in small watershed by semi variance function, explain the spatial structure and self correlation of trace element distribution in small watershed, it is found that the trace elements of structural and autocorrelation in the space are different, most elements of spatial structure is relatively strong, and is closely related to the inherent relationship of soil, small affected by the influence of random outside. According to the channel conditions and terrain elevation, divided the small watershed into three regions, using Kriging interpolation method analysis the content of trace element in different areas of the watershed. The results show that the upstream and middle reaches of the elements in the region high value area distribution along the river, low value areas are distributed in high altitude and far away from the rivers of the area, the trace element distribution to the low altitude and near the river gathering trend. The distribution of trace elements in the lower reaches is different from that in the upper and middle reaches, and the distribution of the high and low values is random, and no longer along the river. A large number of soil and water conservation measures in the lower reaches of the region have a significant impact on the distribution of trace elements in the region.In order to analyze the influence of different land use types on trace element content further, In the fourth chapter, Statistical analysis of soil trace elements in different land use types of small watershed by using classical statistics method is divided into three steps. Final discovery that the content of trace elements zinc in small watershed is relatively short, but other trace elements are abundant. The distribution of each element in the upper, middle and lower reaches is different, copper and zinc in the surface and layer are same, both of them are middle stream> downstream> upstream, the rule of iron content in the soil is opposite, is upstream> downstream> midstream, the content of Mn showed opposite rule between the surface and the sub layer in the soil. It is surface upstream> middle> downstream, level downstream> middle> upstream. Soil trace elements of different land use types in different regions are different. Only the trace elements of the soil zinc in all regions of the different land use types performance as farmland> grassland> trees and shrubs land. The trace elements content of trees and shrubs land in the regional are not the highest, but are the most stable. The change trend of copper and iron content in different regions are even an opposite phenomenon in the change of the total average value. Four kinds of trace elements in bamboo land are all at a high level in the three regions, but with regional changes, trace elements in bamboo land are same with the total average value changes, trace elements remain ability in bamboo land is weak.At the end of this paper, the characteristics and shortcomings of the paper are discussed. To provide reference for the practical application of land and related research.