黄土区退耕草地小尺度土壤水分空间异质性

Soil water content heterogeneity at small-scale on degraded grasslands on Loess Plateau

通过在黄土高原水蚀风蚀交错带选取3块不同年限退耕草地,进行高密度、高频度样带采样,研究分析在表层土壤干旱和湿润状况下,小尺度表层土壤含水率的空间异质性,并分析改变采样间距对土壤含水率空间异质性的影响。结果表明:小尺度表层土壤水分空间异质性为12 a退耕草地>20 a退耕草地>5 a退耕草地;空间变异强度表现为干旱时为中等变异>湿润时为弱变异;表层土壤水分方差与含水率均值呈正相关,土壤水分方差随含水率均值增大而增大;表层土壤水分空间连续性为12 a退耕草地>20 a退耕草地>5 a退耕草地,且与表层土壤含水率呈负相关;小尺度下改变采样间距,在土壤干旱和湿润时均不改变3块退耕草地表层土壤水分空间变异程度。

In order to explore the heterogeneity of topsoil water content （SM） of regressed grasslands at small-scale, three regressed grasslands in water-wind erosion crisscross region on Loess Plateau were selected. By using high sampling-density and high frequency sampling methods at three sampling transects, we explored the heterogeneity of topsoil water content when the surface soil was in dry and moist conditions and different sampling spaces at small-scale. Results showed that the heterogeneity of topsoil water content of different regressed grasslands followed a sequence of 12 a 〉 20 a 〉 5 a and it presented medium variation when topsoil was dry. Topsoil water content was positively correlated with its variance value, that is the variance of SM increased with SM increase. Spatial continuity of SM followed a sequence of 12 a regressed grassland 〉 20 a regressed grassland 〉 5 a regressed grassland and it was negatively correlated with topsoil water content. At different sampling spaces at small-scale, the variation intensity of topsoil water content under different regressed grasslands had no change whenever the topsoil was dry or moist. This information may provide scientific proofs for water reasonable utilization and vegetation restoration on the Loess Plateau.