Relationship between Population Characteristics of Artemisia Scopariain and Soil Factors in Desert Steppe
Ningxia desert grassland is mainly distributed in arid and semi-arid climate area,accounting for about 55%of the total grassland area,which is an important barrier to the ecological environment of Ningxia.In recent years,with the implementation of policies such as returning farmland to forestry and grassland,closing off grazing and ecological migration,the regional ecosystem will recover itself after eliminating the disturbance of human and livestock,and the vegetation coverage has been significantly improved.However,in the early stage of the restoration of deserts and grasslands,there is a lack of scientific management and a lack of understanding of the structure and function of grassland ecosystems,such as Artemisia scopariain which is a non high quality forage,occupies as many as 1/4 of grassland in the middle part of Ningxia’s Yanchi desert,making the vegetation structure and quality of desert steppe poor.Therefore,based on the method of point location in different zero models(complete spatial random model,Poisson cluster model and nested double-cluster model),this study has a preliminary understanding of the distribution pattern of the initial life history of A.scoparia populations in desert grassland,calcareous soil,aeolian sandy soil and weathering bedrock.On the basis of this method,37 typical plots of A.scoparia communities were selected by random sampling method in the central desert steppe of Ningxia.The growth characteristics and soil factors data of A.scoparia were obtained through field investigation and laboratory tests.Soil factors and distribution indices of A.scoparia were studied by one-way ANOVA.Statistical analysis,and analysis of the relationship between soil physical and chemical factors.The relationship between growth characteristics and soil factors of A.scoparia under different soil conditions was analyzed by RDA.The growth distribution law and soil influence factors of A.scoparia in desert steppe were comprehensively analyzed,providing theoretical basis for reasonable management of A.scoparia and improving vegetation structure and quality.The main results are as follows:(1)Within a certain scale,the population of A.scoparia on different soil types showed aggregated distribution on a small scale.In order to further reveal the characteristics of aggregation distribution,Poisson distribution model and nested double lump model were used to analyze the distribution pattern of A.scoparia population on the weathering bedrock soil.The distribution pattern of A.scoparia population on aeolian sandy soil and sierozem soil conforms to the nested double lump model,that is,there are relatively dense small aggregates in the fast growing process.(2)The population characteristics of A.scoparia n in Ningxia desert grassland are quite different under different soil types.In general the height coverage,density,crown and biomass of A.scoparia are all aeolian sandy soil>sierozem soil>weathering bedrock soil in different soil types.There is a significant or very significant positive correlation between height and coverage,crown and biomass of A.scoparia There was a significant positive correlation between density and coverage of A.scoparia and a significant negative correlation between crown density and coverage.(3)The contents of organic carbon,active organic carbon,nitrogen,phosphorus,potassium,available nutrients,pH value,conductivity and water content in different soil types were different.The average content of soil organic carbon and conductivity in different soil types are as follows:weathering bedrock>sierozem soil>aeolian sandy soil.The content of organic carbon in the three soil types showed vertical distribution characteristics,and the content of organic carbon in the surface layer(0-5cm)was significantly higher than that in the deep layer,showing enrichment.The electrical conductivity of aeolian sandy soil shows a trend of decreasing first and then increasing.The average content of soil easily oxidized organic carbon and total nitrogen in different soil types is sierozem soil>aeolian sandy soil>weathering bedrock.The content of soil total nitrogen in three soil types showed a vertical distribution,that is,with the increase of soil depth,the average content of soil total nitrogen decreased.The average contents of water-soluble organic carbon,available phosphorus and alkali-hydrolyzed nitrogen in soils of different soil types were as follows:aeolian sandy soil>sierozem soil>weathering bedrock.Average content of available phosphorus in three soil types showed obvious vertical distribution characteristics,that is,the content of available phosphorus decreased with the increase of soil depth.The content of alkali-hydrolyzed nitrogen in aeolian sandy soil shows a vertical distribution,that is,with the increase of soil depth,the content of soil alkali-hydrolyzed nitrogen decreases continuously.The average contents of total phosphorus and water in soils of different soil types are as follows:sierozem soil>weathering bedrock>aeolian sandy soil.There was no significant difference in total phosphorus,pH value and average moisture content among different soil types.The soil pH value of different soil types increased with the increase of soil depth.The correlation between soil factors is different and complex in different soil types.(4)The correlation between population characteristics and soil factors of A.scoparia is different under different soil types.In general,soil moisture is an important factor to promote Artemisia scopariain growth.Soil hardness is an important factor to inhibit the growth of A.scoparia.The effects of other soil factors on the quantitative characteristics of A.scoparia are different in different soil types.