Study On Soil Quality Evaluation And Its Influencing Factors In Desert Grassland Area Of Siziwang Banner

The grassland area of Inner Mongolia is an important animal husbandry production and breeding base and natural pasture in China.The desert grassland area of Siziwang Banner is a key area for the ecological construction of two screens and three belts in China.This area is located in an arid and semi-arid climate area with fragile ecological environment.At present,the ecological restoration of degraded grassland has attracted the attention of many scholars and previous local governments,Accurate soil quality assessment of desert grassland is of great significance to the improvement and construction of grassland ecological environment.In this paper,the study area is selected in the desert grassland area of Siziwang Banner.38 sampling points are selected through the systematic grid sampling method to measure the physical,chemical and biological indexes of the desert grassland soil in the study area,and study and analyze its spatial distribution characteristics;With the help of principal component analysis,minimum data set and comprehensive evaluation method of soil quality,the soil quality evaluation data set of desert grassland is established,and the evaluation index system is established to evaluate the soil quality of desert grassland area;This paper analyzes the factors affecting soil quality from two aspects of nature and humanity,in order to provide data reference for the establishment of local soil quality evaluation index system and provide theoretical basis for grassland ecological construction and grassland management.The main conclusions are as follows:(1)The spatial variation of main soil chemical indexes in the study area is large.With the deepening of soil layer,the content of organic matter,total nitrogen,available nitrogen,available phosphorus and available potassium gradually decrease,and there is a phenomenon of surface agglomeration.According to the national soil nutrient classification standard,the content of organic matter is at Level 3,the content of total nitrogen is at level 4,the content of available nitrogen is at level 4,the content of available potassium is at level 5 and the content of available phosphorus is at level 4,which is in a relatively deficient and deficient state as a whole.With the deepening of the soil layer,the p H value of the soil increases gradually and is alkaline as a whole;The spatial variation degree of physical indexes is large.The soil mechanical composition is mainly composed of sand(55.22%-68.13%),followed by silty sand(30.49%-41.43%),and clay(1.11%-2.89%)accounts for the least.With the deepening of soil depth,the content of soil clay and silty sand gradually increases,and the content of sand gradually decreases.The study area is mainly affected by wind erosion and hydraulic erosion.Wind erosion accounts for the majority and hydraulic erosion accounts for a small part.The number of samples in areas with moderate wind erosion is the largest,and the degree of wind erosion is at a high level.The soil bulk density and soil water content are distributed in a strip in space.The soil bulk density is the maximum in the north of the study area and the minimum in the south of the study area.The soil water content in the south of the study area is the largest and the soil water content in the north of the study area is the smallest,showing a spatial transition trend,but the change trend is opposite;The main biological indexes of desert grassland area show a transitional trend in space,which is distributed in strips.The biomass in the southeast is higher,the biomass in the northwest is smaller,and the biomass increases gradually from the northwest to the southeast.(2)14 soil quality evaluation indexes were selected as the evaluation factors of the total data set,and the principal component analysis method and norm value were used to calculate.Finally,the evaluation indexes of the minimum data set were determined as organic matter,sand,soil erosion degree and p H value;The calculation result of soil quality index(SQI)is 0.21.According to the national soil quality classification,the soil quality grade of desert grassland in the study area belongs to a low level.(3)The slope direction has a significant correlation with the content of available phosphorus and available nitrogen.In the southwest,the content of available nitrogen and available potassium reaches the maximum;The soil bulk density decreases with the increase of slope,on the contrary,the soil water content increases gradually with the increase of slope;With the increase of elevation,the content of soil organic matter,total nitrogen,available nitrogen,available phosphorus,aboveground biomass,water content and microbial diversity increased,and the p H value,soil bulk density and soil erosion intensity decreased with the increase of elevation;Climate conditions affect soil quality.With the increase of temperature,the content of organic matter,total nitrogen,available nitrogen,available potassium,available phosphorus,aboveground biomass,water content and microbial diversity gradually decrease,and the intensity of soil erosion and soil bulk density also increase;Precipitation increased with organic matter content,available phosphorus content,available nitrogen content,aboveground biomass,total nitrogen,water content and microbial diversity,which was inversely proportional to p H value,soil erosion intensity and soil bulk density;Different soil types have different effects on soil quality elements.Soil types have significant differences with soil organic matter content,available nitrogen content and soil bulk density(P < 0.05),and have extremely significant differences with aboveground biomass,soil water content and microbial diversity(P < 0.01);Land use types have little effect on the soil quality of and desert grassland,and there are significant differences in soil bulk density under different land use modes;Population per unit area(POP)has a strong correlation with soil organic matter content,soil total nitrogen content,soil available nitrogen content,soil available phosphorus content,aboveground biomass,soil bulk density,soil water content and microbial diversity.In addition to a significant negative correlation with soil bulk density,Pop has a positive correlation with other correlation indicators;GDP level has a strong correlation with soil organic matter content,soil available phosphorus content,soil available nitrogen content,aboveground biomass,soil total nitrogen content,soil bulk density,soil water content and microbial diversity.In addition to a significant negative correlation with soil bulk density,it has a positive correlation with other correlation indicators.