然林及坡耕地转变为巨桉林后土壤抗蚀性变化

以川西低山区天然林及其人工更新形成的1年生（Ⅰ1）、2年生（Ⅰ2）和3年生（Ⅰ3）巨桉林,坡耕地及其退耕形成的1年生（Ⅱ1）、2年生（Ⅱ2）和3年生（Ⅱ3）巨桉林为研究对象,研究土壤抗蚀性变化。结果表明：天然林转变为巨桉林后土壤水稳性团聚体平均重量直径、结构性颗粒指数、团聚状况和团聚度降低,土壤不稳定团粒指数、分散率、侵蚀系数和受蚀性指数增加;相反,坡耕地转变为巨桉林后土壤水稳性团聚体平均重量直径、结构性颗粒指数、团聚状况和团聚度增加,土壤不稳定团粒指数、分散率、侵蚀系数和受蚀性指数降低。土壤抗蚀性综合主成分值呈现出天然林〉Ⅰ1〉Ⅰ3〉Ⅰ2及坡耕地〈Ⅱ1〈Ⅱ2〈Ⅱ3变化规律。说明天然林改为巨桉林后土壤抗蚀性会有所降低,但随着种植年限的增加土壤抗蚀性有上升趋势,而坡耕地改为巨桉林后土壤抗蚀性随种植年限的增加而增加。

Effects of Converting Natural Forest and Slope Farmland to Eucalyptus grandis plantations on Soil Erosion Resistance

In this paper,studies are made of soil erosion resistance under 1（Ⅰ1）,2（Ⅰ2） and 3（Ⅰ3） year-old Eucalyptus grandis regenerated plantations resulted from natural forests and 1（Ⅱ1）,2（Ⅱ2） and 3（Ⅱ3） year-old Eucalyptus grandis plantations resulted from slope land in low mountain areas of western Sichuan province.The results showed that the Eucalyptus grandis plantation resulted from natural forest would lead to the mean weight diameter of its soil water-stable aggregates,structural granular index,aggregation state and aggregation rate to decrease,and the index of unstable aggregate,dispersion ratio,erosion coefficient and index of erodibility to increase.In contrast,the Eucalyptus grandis plantation resulted from slope farmland would lead to the mean weight diameter of its soil water-stable aggregates,structural granular index,aggregation state and aggregation rate to increase,and the index of unstable aggregate,dispersion ratio,erosion coefficient and index of erodibility to decrease.The synthetic principal component score value of soil anti-erodibility ranked as natural forestⅠ1〉Ⅰ3〉Ⅰ2,and slope farmland 〈Ⅱ1〈Ⅱ2〈Ⅱ3.This indicated that soil erosion resistance could decrease in initial conversion of natural forest to Eucalyptus grandis plantation,however this trend would delay with the plantation year increase;Conversion of slope farmland to forestland could increase soil erosion resistance with the plantation year increase.