Study On The Spatial Variation Characteristics And Correlation Of Soil Vegetation In The Nitraria Tangutorum Nebkhas

This study patterns in the desert grassland in the ecotone between agriculture and animal husbandry as the research background,with the Nitraria tangutorum Nebkhas as the research object,the quantitative analysis of the morphological characteristics.morphological parameters,spatial pattems.soil properties and spatial variation of Nitraria tangutorum community in desert steppe, to explore the formation and development of Nitraria tangutorum nebkhas,and reveal spatial variation characteristics of soil,vegetation and the relationship of Nitraria tangutorum Nebkhas.It has certain theoretical value and practical significance to the ecological restoration and reconstruction of the region and even the desert steppe.Through field investigation,sampling and indoor sample analysis and data statistics.the following conclusions are obtained:(1)The mature stage of the Nitraria tangutorum nebkhas accounted for the majority.At different stages of development,the distribution pattern of the Nitraria tangutorum nebkhas is different.In the primary stage, development stage and mature stage.the main performance of the nebkhas is the aggregation distribution,and in the decline stage.the nebkhas is distributed as a random distribution pattem.At different scales.the distribution pattern is different.At a small scale (0-10m).the nebkhas is distributed randomly.and the 10m-40m scale,which is the aggregate distribution, is distributed in the 40m-50m scale.(2)There are many difference in morphological characteristics of different stages of Nitraria tangutorum Nebkha in the desert steppe. With the evolution of the nebkha,Change the length,height, windward and leeward slope angle increases,And the long axis,short axis and the height of the nebkha increase cooperatively.Long axis growth is stable.the short axis has a significant increase in the end of the evolution,high growth to maintain a smooth.the relationship of the major axis and the short axis.Long axis and height,Long axis and surface area,Long axis and volume.height and surface area,height and volume in nebkha are from weak to strong,the relationship between slope angles (including the’windward and leeward slope) and other parameters are week.(3)The water storage capacity of various parts of the Nitraria tangutorum nebkhas is:the external> the edge> the inside.The 20-40cm soil moisture content was highest in the nebkhas.and the 60-80cm in the edge of the nebkhas was highest,and the the 80-100cm in outside of the nebkhas was highes.The content of soil organic matter and total nitrogen with nebkhas from center distance to outside increased and significantly (P< 0.05) decreased (i.e. nebkhas inside> nebkhas edge> nebkhas outside) showed Nitraria tangutorum nebkhas has "fertile island, However, the fluctuation range of available phosphorus is smaller than that of soil organic matter and total nitrogen, and there is no significant difference between soil layers (P>0.05). Nitraria tangutorum nebkhas in different parts of soil microbial number is:nebkhas inside> nebkhas edge> nebkhas outside, with from nebkhas center distance increasing, the number of soil bacterial and actinomycetes were significantly reduced,and the number of fungi gradually increased.In the process of the evolution of the Nitraria tangutorum nebkhas, there is a trend toward reduced of the soil water content in the soil.Soil moisture content increased at 20-40cm,and then decreased.Soil bulk density increased with the increase of soil layer.The content of organic matter and total nitrogen in soil was the highest in the mature stage.and the amount of 0-20cm was accumulated in a large amount,and the available phosphorus content reached the highest level in the development stage.Nutrients are mostly accumulated in 0-20cm soil. At different stages of evolution.the number of soil microorganisms was significantly different. With the evolution and development of the Nitraria tangutorum nebkhas.the number of bacteria decreases and then decreases,the number of actinomycetes increases and the number of fungi decreases and then increases.(4)Different stages of succession,the species composition of the communities of Nitraria tangutorum nebkhas is different.In the early stages of development,gramineous plants dominant,and to a mature stage,chenopodiaceous plants occupy the main part,the diversity index,evenness index and dominance index were all low.The level of species diversity was significantly higher than that in the primary stage and the decline stage.and the species evenness was significantly higher than that in the other stages.(5)In the primary stage.Nitraria tangutorum nebkhas coverage and volume are closely related,and is a linear function of growth mode;in the developmental stage,with Nitraria tangutorum vegetation coverage increased,nebkhas volume presents power function growth model;in the mature stage.the Nitraria tangutorum coverage of nebkhas has a number of function growth model, with the increase of coverage,the volume of the nebkhas is gradually increasing.In the decline stage,there is no significant correlation between the volume and coverage of the shrub.In different developmental stages.the soil and vegetation in the Nitraria tangutorum nebkhas showed a significant correlation between the soil and the vegetation; The maximum value of correlation coefficient between vegetation index and water content and bulk density appeared in the initial stage, and the maximum value of the correlation coefficient between soil organic matter and total nitrogen content appeared in the mature stage.There was no significant relationship between soil bacteria,fungi, actinomycetes and community characteristics.