Study On Spatial Heterogeneity Of Soil Nutrients And Its Influencing Factors In Picea Schrenkiana Var. Tianschanica Forest

To study the spatial heterogeneity of soil nutrients and its influencing factors in Picea schrenkiana var.tianschanica forest,this study took Picea schrenkiana as the research object.In combination with field investigation and laboratory analysis,the spatial variability of soil nutrients in Picea Schrenkiana was studied basis on geo-statistics and GIS technology.The influence mechanism of multi-factors on soil nutrients were discussed in combination with RDA analysis.Finally,the soil fertility index(SFI)was calculated by principal component method.The soil fertility level under different altitude,canopy density and stand age was analyzed by systematic cluster analysis method,based on the reference of the ecological restoration of mountain forest ecosystem in Xinjiang and the sustainable management of Picea schrenkiana.The main results are as follows:(1)The variation coefficients of soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen,available phosphorus,available potassium and p H in 0～20 cm soil layer of Picea schrenkiana var.tianschanica forest ranged from 11.04% to 66.84%.The variation coefficient of each nutrient index in20～60 cm soil layer ranged from 12.17% to 61.02%,all of which belonged to moderate variation.The nugget coefficients of soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen and available potassium under different soil layers of Picea schrenkiana ranged from 8.8% to 19.1%,showing strong spatial autocorrelation,which means that they were mainly affected by structural factors;Available phosphorus belonged to moderate spatial autocorrelation,and the variation was affected by a combination of random and structural factors.The p H value of 0～20 cm soil layer showed strong spatial autocorrelation,while the p H of 20～60 cm soil layer belonged to moderate spatial autocorrelation.(2)By RDA analysis,the explanatory degrees of environmental factors on spatial variability of soil nutrients in Picea schrenkiana var.tianschanica forest are as follows: Soil water content > soil bulk density > soil depth > soil p H > stand age > canopy density > altitude > slope > aspect > slope position.Seven of the environmental factors above significantly affected soil nutrient content in the study area,and the selected environmental factors explained 57.2% of the variation information of soil nutrient in Picea schrenkiana.(3)The results of soil nutrient characteristics and fertility quality evaluation of in Picea schrenkiana var.tianschanica forest showed that the carbon and nitrogen content of 0-20 cm under the gradient of 1900-2 100 m is the highest,and the comprehensive score of soil fertility under this altitude gradient is the highest(0.72),of which 22.5% of the soil fertility reaches grade I and grade II level;The content of soil carbon and nitrogen showed an increasing trend with the increase of stand age.There was a significant difference in the content of soil carbon and nitrogen in 0-20 cm soil layer between mature forest,young forest or middle-aged forest(P<0.05).The comprehensive score of soil fertility of mature forest is 0.86,of which 35.71% of soil fertility reaches grade I and grade II level;Under the condition of high canopy density,the content of soil carbon and nitrogen in 0-20 cm soil layer of Picea schrenkiana forest was significantly higher than that under the condition of low canopy density(P<0.05),the comprehensive score of soil fertility under high canopy density was higher(0.74),and 29.03% of the soil fertility reached grade Ⅰ and grade Ⅱ level.