杉木成熟林土壤容重空间变异特征

为探明土壤容重空间变异特征及其采样间距,以杉木成熟林为研究对象,选取100 m×100 m区域,利用网格法(10 m×10 m)设置样地共计100个,采用经典统计学与地统计学方法分析研究区内不同土壤深度(0~20、20~40 cm)土壤容重的空间异质性,并进行再采样探寻该尺度下最佳采样间距及采样数,旨在减少土壤容重采样人力和物力的消耗。结果表明:土壤容重及其变异系数随土层增加而增加,中等变异,0~20、20~40 cm最佳模型分别为指数模型、球状模型,空间分布呈斑块状,属中等空间自相关;采样间距增大会导致采样数呈"减小-稳定-极限"的变化趋势,变异系数变化虽不大,却能获得更为真实的土壤容重变异系数,20 m×20 m采样间距以下空间自相关性变化程度、拟合效果、块金值等参数较好,小尺度(100 m×100 m)空间变异分析时,采样间距20 m×20 m、采样点布设25个,既能满足Kriging插值精度,又能节省人力和物力。

Spatial variation characteristics of soil bulk density in mature forest of Cunninghamia lanceolata

In order to find out the spatial variation characteristics and sampling spacing of soil bulk density,100 m×100 m area was selected for the mature forest of Cunninghamia lanceolata,and a total of 100 plots were set up by grid method(10 m×10 m).The spatial heterogeneity of soil bulk density in different soil depths(0-20,20-40 cm)was analyzed by classical statistics and geostatistics,and the optimal sampling spacing and sampling number were explored by"resampling".The purpose of this paper is to reduce the consumption of manpower and material resources for soil bulk density sampling.In this study:the soil bulk density and the coefficient of variation of soil increase with the increase of the soil layer,the coefficient of variation is middle variation,0-20 cm,and the optimal model of 20-40 cm is the exponential model and the spherical model,and the spatial distribution is plaque-like,and belongs to the medium-space self-correlation.The increase of sampling spacing will lead to the pattern of"decrease-stability-limit"of sampling number.Although the coefficient of variation does not change much,it can obtain a more real coefficient of variation of soil bulk density.The variation degree of spatial autocorrelation,fitting effect and nugget below20 m×20 m sampling spacing are better.In the analysis of spatial variation in small scale(100 m×100 m),the sampling spacing is 20 m×20 m and the sampling number is arranged 25,which can not only meet the accuracy of Kriging interpolation,but also save manpower and material resources.