全球土壤可蚀性因子砾石效应的影响因素研究

为了全面认识土壤中的砾石对土壤可蚀性因子(K)的影响,即砾石效应(stoniness effect on erodibility,SE_K),利用全球范围的砾石覆盖影响(S_t),剖面砾石影响(K_cf)、砾石覆盖和剖面砾石综合影响(K_f-cs)以及高程、坡度、坡向、植被覆盖、土地利用类型、多年平均降雨量、多年平均气温等环境要素数据,通过相关性分析、格局分析以及随机森林回归分析,探索了SE_K的空间格局以及影响SE_K的主控因素。结果表明:(1)高程和坡度与SE_K呈正相关; 植被覆盖度、降雨量和温度与S_t和K_f-cs呈负相关; 降雨量与K_cf呈负相关; 温度与K_cf呈正相关; 阳坡的砾石效应大于阴坡; 耕地和林地的砾石效应较小,草地、荒漠和裸地的砾石效应较大。(2)S_t和K_f-cs的主控因子为高程和坡度,降雨量和温度是K_cf的主控因子。因此,在大区域土壤侵蚀评价中,对于砾石含量较大、高程较高、坡度较大的区域,均应给予特别关注,如果不加考虑,则有可能使土壤侵蚀评价结果出现偏差。

Research for the Factors Influencing the Stoniness Effect on Erodibility at Global Scale

In order to comprehensively understand the effect of rock fragments in the soil on the soil erodibility factor(K), i.e. the stoniness effect on erodibility(SE_K), the effect of rock fragments on the surface(S_t), the effect of rock fragments in profile(K_cf), the joint effect of rock fragments in profile and rock fragments on the surface(K_f-cs)and some environmental factors such as elevation, slope, slope aspect, vegetation coverage(NDVI), land use, annual average precipitation and annual average temperature at a global scale were used to explore the spatial pattern of SE_K and the main controlling factors affecting SE_K through correlation analysis, pattern analysis and random forest regression analysis. The results show that:(1)elevation and slope are positively correlated with SE_K; vegetation coverage(NDVI), precipitation and temperature are negatively correlated with S_t and K_f-cs, precipitation is negatively correlated with K_cf, and temperature is positively correlated with K_cf; the influence of rock fragments on southern(sunlit)slopes is found to be greater than that on northern(shaded)slopes; the influence of rock fragments on cropland and forest is slight, while the influence of rock fragments on grassland, desert and bare land is relative heavy;(2)the main controlling factors of S_t and K_f-cs are elevation and slope; the main controlling factors of K_cf are precipitation and temperature. Therefore, in the evaluation of soil erosion in large regions, special attention should be paid to areas with large content of rock fragments, higher altitude and higher slope, otherwise the evaluation results of soil erosion will be biased.