不同采样幅度和间距下压砂地枣树土壤水分的空间变异性研究

为了探明西北地区特有的压砂地枣树土壤水分的空间变异及其尺度效应,本文基于野外试验,选取32m×32 m区域,并在此基础上改变采样幅度和采样间距,基于经典统计学和地统计学理论,研究了不同采样幅度和间距条件下0-50 cm土层土壤含水量的空间分布特征及其空间变异性。结果表明,对于所有5种采样幅度(32m×32 m、28 m×28 m、24 m×24 m、20 m×20 m和16 m×16 m),随土层深度的增加,土壤含水量呈减小的趋势,而变异系数呈增大的趋势,空间变异强度基本表现为弱变异至中等偏弱变异;当采样幅度增大时,土壤含水量的变异系数Cv、块金值C0及变程A均不断增大。对于4 m、8 m和12 m这3种采样间距,当采样间距增大时,土壤含水量的块金值C0不断增大,变程A不断减小,而变异系数Cv不受影响。在不同尺度内,土壤含水量均存在强烈的空间自相关性。各土层土壤含水量在不同采样间距下的空间分布形态相似,多处出现明显的"隆起"与"凹陷",受地形影响显著,并随着采样间距的增大,逐渐平坦化,8 m为较合理的采样间距。

Effects of sampling extent and spacing on spatial variability of soil water content in a field with gravel-mulched jujube tree

To explore the effects of sampling extent and spacing on spatial variability of soil moisture in a gravel-sand mulched jujube orchard, spatial analyses including classical statistics and geo-statistics were conducted with soil water content (SWC) of 0-50 cm in the 32 m×32 m field by changing the sampling extent and spacing. Irrespective of sampling extents (i.e. 32 m×32 m, 28 m×28 m, 24 m×24 m, 20 m×20 m and 16 m×16 m), the SWC decreased with the increase of soil depth while the variation coefficient increased with the increasing soil depth. The spatial variability of SWC was weak and moderate for all scales; The variation coefficient (Cv), nugget (C0), and variation range (A) of SWC all increased with the increase of sampling extent. When three sampling spacings (i.e. 4, 8 and 12 m) were concerned, the nugget (C0) increased with the increase of sampling spacing; The variation range (A) decreased with the increase of sampling spacing; the Cv was not affected by the sampling spacing. A strong spatial autocorrelation characteristic of SWC was found for all scales. The distribution patterns of SWC in the same soil layer at different sampling spacings were similar and tended to be "flat" with the increase of the sampling spacing. The reasonable sampling spacing was found to be 8 m in our case.