新疆草地土壤厚度及与地形特征的相关性

Soil Depth of Grassland in Xinjiang and the Correlations with Terrain Attributes

使用传统野外土壤调查的方法,2011~2013年在新疆不同草地类型区调查了577个典型样地的土壤剖面。按照《全国水土保持区划》,比较了新疆不同水土保持区的土壤厚度。运用GIS技术和相关分析的方法,探讨了海拔、坡度、坡向、平面曲率和剖面曲率等5个地形特征参数与土壤厚度之间的相关性。结果表明：新疆草地平均土壤厚度为68.9cm,348个样地的土壤厚度〈100cm,占样地总数的60.3%,表明新疆草地土壤总体较薄。各水土保持区中,土壤厚度最高的是塔里木盆地南部,最低的是吐哈盆地,这可能与成土母质类型有关。在坡度〉15°或者海拔在1000~1500m之间时,草地土壤的厚度通常较低。在新疆自治区尺度,5个地形特征指标与土壤厚度的相关性均不显著。但在塔里木盆地北部,海拔、坡度和坡向与土壤厚度相关关系均为极显著（P〈0.01）,表明在较小的地貌单元建模,有望提高土壤厚度的预测精度。

Using traditional field soil survey method,soil profiles of 577 typical plots with different grassland types were surveyed from 2011 to 2013.Soil depths among different main soil and water conservation zones in Xinjiang were compared,according to the National Soil and Water Conservation Zoning of China.Five terrain attributes,i.e.,altitude,slope,aspect,plan curvature,and profile curvature,and their impacts on soil depth were investigated by using GIS technique and correlation analysis method.The results showed that the average soil depth of grassland in Xinjiang was 68.9cm.Soil depths of 348 surveyed plots were lower than 100 cm,accounting for 60.3% of the total number of surveyed sites,showing soil of grassland in Xinjiang was generally low.Among the main soil and water conservation zones,soil depth of the southern Tarim basin zone was the highest,while that of the Turpan-Hami basin zone was the lowest,which was probably influenced by parent material.Soil depth was often low when the slope was larger than 15°,or the altitude was between 1000 mto 1500m.All correlation relationships between each of the five terrain attributes and soil depth were not significant at Xinjiang autonomous region scale.However,extremely significant correlation relationships existed among altitude,slope,aspect,and soil depth in Northern Tarim basin zone（P0.01）,suggesting that modeling soil depth at small geomorphologic unit could improve prediction efficiency.This study gives some suggestions for digital soil mapping in grassland of Xinjiang.