漓江源头大溶江流域土壤理化性质

Spatial differences of soil physical and chemical properties in Darongjiang river watershed

文章采用ArcGIS和SPSS22.0软件分析珠江三级支流漓江上游大溶江流域内土壤pH、电导率、粒度、土壤总氮(TN)、土壤有机碳(TOC)、土壤无机碳(TIC)及其在空间上的分布特征,结果显示:(1)研究区土壤pH平均值在土下20 cm处为4.04~6.23,土下50 cm处为4.02~6.53,体现出土壤的地带性特征,土壤电导率均值为352.93μs·cm^(-1)(变化范围为145.00~1015.00μs·cm^(-1)),流域内不同地质背景的土壤pH和土壤电导率具有显著差异性;(2)土壤粒径以粉粒含量最高(59.39%),其次是沙粒(33.26%),黏粒含量最低(7.36%),黏粒和粉粒含量随土壤深度增加而增加,沙粒含量随土壤深度的增加而减少;土壤体积含水量为22.04%~46.45%,在土下20 cm处土壤体积含水量均值为31.55%,在土下50 cm时土壤体积含水量均值为30.98%;(3)流域内土壤的TN、TOC和TIC平均含量分别为1.50 g·kg^(-1)、15.25 g·kg^(-1)、16.89 g·kg^(-1),其空间分布与土地利用类型一致,均表现为林地高、耕地低的特征;垂直分布上,土壤中碳、氮含量随着土壤深度增加而降低,主要是由于表层土壤最先接收枯枝落叶等腐殖质的分解,使碳、氮等营养物质在地表富集所致;(4)流域内土壤TOC、TIC、TN均与黏粒、粉粒含量呈负相关,与沙粒含量呈正相关,pH与黏粒、粉粒含量呈正相关,与沙粒呈负相关;流域内土壤TN与TIC、TOC均呈极显著正相关,与电导率呈显著负相关;TIC含量和TOC含量之间具有极显著正相关关系,与体积含水量和电导率呈显著负相关。

The study on physical and chemical properties of soil in watershed is the basis for soil nutrient management and rational fertilization.The Darongjiang river is the upper reach of the Lijiang river,the third level tributary of the Pearl River.The physical and chemical properties of soil and their characteristics of spatial distribution in Darongjiang river watershed are analyzed,and the research findings are of great significance for agricultural activities in this watershed as well as for the protection of Lijiang river.The results show as follows,(1)The average pH values of soil are 4.04-6.23(soil samples are taken in 20 cm under the surface)and 4.02-6.53(soil samples are taken in 50 cm under the surface),which present the Zonal characteristics of soil.The average electricity conductivity(EC)is 352.93μs·cm^(-1) with the range of 145-1,015μs·cm^(-1).The values of soil pH and EC in different geology backgrounds demonstrate a significant difference in the study area;(2)The soil particle composition in the watershed is dominated by silt(59.39%),followed by sand particle(33.26%)and clay(7.36%).And the sand particle decreases with the increase of sampling depth,while the content of clay and silt increases.The volumetric moisture content of soil ranges from 22.04% to 46.45%,with an average of 31.55% in 20 cm under the surface and an average of 30.98% in 50 cm under the surface;(3)The average concentration of total nitrogen(TN),total organic carbon(TOC),and total inorganic carbon(TIC)are respectively 1.50 g·kg^(-1),15.25 g·kg^(-1) and 16.89 g·kg^(-1).The spatial distribution of TN,TOC and TIC conforms to different types of land use,namely,the concentration is higher in forest and lower in cultivated land.Moreover,the nitrogen content decreases with the increase of soil depth,mainly because the decomposition of humus such as deadwood and fallen leaves enriches carbon,nitrogen and other chemical substances in the surface soil;(4)The concentration of TOC,TIC and TN in soil is negatively correlated with the content of clay and silt,and positively correlated with the content of sand particle.By contrast,the pH value of soil is positively correlated with the content of clay and silt,and negatively correlated with the content of sand particle.The soil TN is of a significant positive correlation with TOC and TIC,but of a negative correlation with electricity conductivity.The concentration of TIC is of a great positive correlation with that of TOC and of a significant negative correlation with volumetric water content and electricity conductivity.