紫色土坡耕地土壤物理性质空间变异对土壤侵蚀的响应

Response of spatial variability of soil physical properties to soil erosion in purple soil slope farmland

为了研究不同坡度和坡长的耕地上土壤侵蚀对土壤物理性质空间变异的影响,通过地形测量、137Cs示踪、土壤物理性质分析等方法对川中丘陵紫色土区土壤物理性质对土壤侵蚀的响应进行了研究,结果表明:在中等坡度(16.60%～25.10%)的梯坡地上,耕作侵蚀处于主导地位,是导致耕层土壤物理性黏粒含量和容重在梯坡地上总体差异不大(CV<6.3%),且与137Cs含量不相关的主要原因;在已退耕还林的陡梯坡地上(35.60%),水蚀占据主导地位,导致耕层土壤物理性黏粒含量和容重均与137Cs的含量显著相关。在长坡耕地上(10.10%),具有分选搬运能力的水力侵蚀占据主导地位,致使耕层土壤物理性黏粒含量与137Cs的含量具有显著的相关关系,而容重却与137Cs含量没有显著的相关关系。川中丘陵区坡耕地上,耕作侵蚀和水蚀共同作用于土层深度,使土层深度在坡顶、上坡最浅,在坡脚最深,顺坡向下逐渐增加。因此,在川中丘陵区不同坡长的坡耕地上,占主导地位的土壤侵蚀类型导致坡耕地上土壤物理性质出现相应的变化。

In order to study the effects of soil erosion on spatial variability of soil physical properties in farmlands with different lengths and slopes, the response of spatial variability of soil physical properties to soil erosion was explored in the Sichuan Basin of China, with topography measurement,^ 137Cs tracer method and analysis of soil physical properties. The results showed that tillage erosion, which was the dominant erosion process on the short slopes with the gradients of 16.6%-25.1%, played an important role in redistributing soil and resulted in no significant variation in soil physical properties （i.e., soil texture and bulk density） of tillage layer along the slope （CV〈6.3%）. Meanwhile, the soil physical properties of tillage layer had insignificant correlation with ^137Cs contents due to tillage erosion. On the steep slope （35.6%）, water erosion was the predominant erosion process due to reforestation, with evidence of ^137Cs contents correlated closely with soil physical properties of tillage layer. Furthermore, on the long slope （10.1%）, water erosion with separation and transport capacity was the predominant erosion process, which resulted in significant variation in soil physical properties with ^137Cs contents, but there was no significant correlation between bulk density and ^137Cs contents. Soil depth was affected both by tillage erosion and water erosion in slope farmlands in the Sichuan Basin of China. The erosion resulted in the fact that the thinnest soil layer was present at the summit and upper slope positions, and there was the thickest soil layer at the foot of the slope. In general, soil depth increased towards the downslope direction. Therefore, due to the differences in the predominant soil erosion process the soil physical properties varied with slope lengths in the Sichuan Basin.