A Study On Spatial Variability Of Soil Properties And Influence Of Vegetation On It At A Catchment Of Southern Jiangsu Province In China

Using geostatistical and GIS methods,we conducted a study to examine the spatial variability and vertical characteristics of soil properties in the topsoil (0-20cm)and its relation to main vegetation types under soil vertical profile based on a case of study on Dengxia catchment,Southern Jiangsu province,China.The results showed:The spatial variability of K value at the studied area was significant difference, with the range from 0.1498 to 0.4981,mean of 0.3316,and variance coefficient of 22.11%;The whole distribution tendency of K value presented belt-shaped obviously and was higher in the northwest than in the southeast,with several high K value centers embedding in the middle and south part of the area.For soil erodibility (K-factor)of different vegetation types in the topsoil(0～20cm),the order was as follows:fallow land＞tea garden land＞farmland＞grassland＞broad-leaved forest land＞microphylla shrub land＞coniferous forest land＞bamboo forest land.The spatial variability of soil nutrients was significant difference,and the variance coefficients followed the order of as total phosphorus(TP)＞available potassium(AK)＞soil organic carbon(SOC)＞total nitrogen(TN)＞pH.The theoretical semi-variogram models of pH and SOC were linear and spherical respectively,but TN,TP and AK of which all was exponential model.The whole distribution tendancy of SOC in the studied area was higher in the north part than that in the southeast part,with the lowest value existing in the middle part just as small block.The TN spatial distribution was similar with the distribution of SOC. The spatial distribution of pH and AK also was higher in the north part than that in the southeast part,with several high centers embedding in the middle and south part of the area,and it fluctuated acutely.But the distribution of TP was higher in the middle part than that in the north and southeast part,with several high centers embedding in the middle part.The vertical variance coefficients of soil nutrients in the same layer by main vegetation types all became smaller with the depth became higher gradually at the area while rice paddy field and farm land was reversed with other vegetation types. and the smallest variance of soil nutrients was in the 40-60cm layer of soil profile.