南方农田土壤容重空间变异性及其尺度效应

Spatial variability and scale effect of soil bulk density of farm land in South China

以南方典型农田作物生长地为试验区,利用经典统计与地统计学方法,分析研究了选定区域不同深度土层(0~10,10~20 cm)土壤容重的空间异质性及其尺度效应,并对试验区农田土壤容重进行空间插值估算.结果表明农田土壤容重变异系数较小,为弱变异.半方差函数分析表明土壤容重的块基比小于10%,田间土壤容重由空间自相关部分引起的异质性程度很大.在尺度效应研究中,随着采样幅度增大,变异系数呈先减小后增大趋势;通过调整采样点位置"再采样"发现,当采样间距增大时,土壤容重变异系数变化幅度很小(6.32%~7.92%),而相关距离却减小.说明当采样幅度一定时,采样间距对土壤容重变异系数的影响很小.通过空间插值估算,绘制等值线图发现两层土壤容重也具有相关联的空间分布规律,且呈显著正相关关系,相关系数为0.76.此外,土壤容重空间变异受人为活动影响程度大.

Taking a typical farm land in South China as the test field, the spatial variability and scale effect of bulk density of soils harvested at different soil depths （0 -10, 10 -20 cm） in the selected field were analyzed by using classical statistical and geostatistical methods, and the spatial interpolation of soil bulk density in the field was estimated. The results indicated that the coefficient of variation （CV） of bulk density was small and the variation was weak. A semi-variogram analysis showed that the C0/（ C0 ＋ C） values of the measured soil bulk density were lower than 10% , indicating the spatial hete- rogeneity resulted from the spatial variability of soil bulk density was significant. For the scale effect,the CV decreased firstly and then increased with increasing sampling interval. By adjusting the location of sampling points （ ＂re-sampling＂ ）, it was found that the CV of soil bulk density was small （6.32% -7.92% ） and the correlation distance decreased when the sampling interval increased. It was sug- gested that the sampling interval affected CV a little after the interval was decreased to a certain value. The spatial distribution pattern of soil bulk density in two layers also showed a spatial correlation based on the density spatial interpolation and contours, i.e. a significant positive correlation with a correlation coefficient of 0. 76. Furthermore, the spatial variability of soil bulk density was affected by human activities largely.