中国水稻土氮密度变异性的幅度效应研究

The effect of different extents on variation of nitrogen density of paddy soils in China

基于全国第二次土壤普查的1 491个水稻土剖面数据,研究了行政区幅度（行政大区、省级、地区级）和土壤区幅度（土壤区、土壤带、土区）下水稻土氮密度的变异情况及其对幅度拓展的响应。结果表明,中国水稻土0-20 cm和0-100 cm土壤平均氮密度为18.7 t.hm^-2和12.4 t.hm^-2,土壤氮素的空间变异性总体随幅度拓展而增大。在不同土壤区幅度下,0-20 cm全氮密度组内和组间变异性随研究区幅度的减小而减小;从土壤区到土区尺度,0-100 cm全氮密度组间变异率从250%左右下降至不足50%,而在行政大区和省级尺度时全氮密度的组间变异性没有太大变化,变异率都小于100%,到地级市尺度时,组间变异率又达到了400%,说明同一地区所选择的研究幅度尺度不一样氮密度变异率差异也很大。因此,在今后的水稻土调查采样设计时,根据不同幅度尺度的变异率大小来选择合适的布点方式和样点数是十分必要的。

Base on second Nation Soil Survey data,the effect of different extent district（region,province,and prefecture） and soil region（soil region,soil zone,and soil sub region） on paddy soil’s nitrogen variation was studied by using 1 490 soil profiles.Result showed that the average soil nitrogen density（SND） of 0-20 cm and 0-100 cm paddy soil were 18.7 t hm^-2 and 12.4 t.hm^-2,respec-tively.The variation of SND increased with enlarged of study area.The SND variation within groups and between groups decreased with reduced area in different extent of soil region.When study extent reduced from soil region to soil sub region,the SND variation within groups decreased 5 times.The SND variation between groups stabled when the study extent reduced from region to province and coefficient of variability（C.V.） are lower than 100%.However,the variation between groups increased dramatically when re-search extent reduces to prefecture（C.V.reaches 400%）.It means different research extent can reach variation result of SND.There-fore,it is necessary to choose right sampling spots and proper sampling number in future’s paddy soil’s survey.