Analysis Of Soil Physicochemical Characteristics And Spatial Heterogeneity Of Rocky Desertification Watershed In Center Of Guizhou Province

Guizhou is a typical distribution area of karst land forms in southwestern China.Soil erosion caused by the destruction of the karst environment has led to the continuous development of rocky desertification.In the process of comprehensive management of rocky desertification,it is important to master the spatial distribution of soil characteristics and fertility status,and to optimize the adjustment of agricultural structure and the management of rocky desertification in the karst region.Therefore,this paper takes the small karst rocky desert watershed as the research object in Chenqi,Guizhou.Total of 580 samples of soil depths of 0-10cm,10-20cm,and 20-30cm were collected from six land use types:paddy field,shrub,grassland,abandoned land,slope land,and secondary forest.Through the experiment to determine indicators data,Using classical statistical and geostatistical methods,describe the statistical characteristics of soil physicochemical properties in the study area,correlation analysis,variance analysis,principal component analysis,and spatial interpolation analysis.Based on the principal component analysis method,the soil fertility of six types of plots was effectively evaluated.The main results were as follows:(1)Descriptive statistical analysis results show that the soil BD,pH,and silt content increase with increasing soil depth,and SMC,SOM,N,P,and K contents were reversed.Except for TP and AP,the remaining soil nutrient contents all reached the national secondary standard.The soil is dominated by silt in the study area,which belongs to sandy silt loam and the pH is neutral and alkaline.From the coefficient of variation,AP(except surface)is a strong variability;silt,pH is a weak variability;other indicators are moderately variable.(2)The results of correlation analysis showed that the correlations among other indicators basically reached significant or extremely significant levels,and the correlation coefficient between SOM,TN,and AN reached 0.966 and 0.814,respectively,except P,TK and pH.The tighter of structure and the porosity lower,the lower the content of water and nutrients that can be contained in the soil.Soil P may be derived from artificial fertilization,and TP and TK are mainly in the form of inorganic phosphate and alkaline mineral potassium salts.Phosphate ions and potassium ions have a significant indication of pH.(3)Analysis of variance showed that soil physical and chemical properties of different land use types were significantly different(P<0.05).Secondary forests,shrubs,grasslands and abandoned lands have high soil nutrient content,but paddy fields and arable land(except phosphorus)is low.It shows that the long-term farming production mode is the main reason for the decline of the ecological environment quality in the study area.Returning farmland to forests and grassland is conducive to the management of the local rocky desertification and the restoration and development of the ecological environment.(4)The results of principal component analysis and fertility evaluation show that TN,AN and sand contributed the most to the soil fertility,followed by SOM and AK to soil fertility.TK,SMC,and pH contributed less to soil fertility,the remaining indicators contribute little to soil fertility.The soil fertility of different land use types was:secondary forest(2.73)>shrub(1.66)>abandoned land(0.34)>grassland(-0.13)>sloping farmland(-1.14)>paddy field(-3.48).Secondary forests and shrubs have better soil fertility;Fertility continues to be restored after land reclamation in abandoned land;Grassland,slope farmland and paddy fields are affected by human factors and have poor soil fertility.(5)Spatial heterogeneity analysis shows that the optimal semi-variance function fitting model mainly includes spherical function,exponential function,J-Bessel function,trigonometric function and Gaussian function.Soil BD,pH,and AP have a strong spatial correlation;SOM,TN,TP,AK,and SMC are moderate spatial correlations;The spatial correlation of TK is weaker;The structural ratios of AN in the 0-10 cm,10-20 cm,and 20-30 cm soil layers were 8%,70%,and 80%,respectively,and the spatial correlation was strong to weak in the vertical direction.In addition,Kriging spatial interpolation results of soil physical and chemical indicators better reflect the spatial distribution characteristics of soil characteristics,and the predicted results are close to the actual observed values.