退耕还林后黑土表层土壤可蚀性动态变化1）

摘要

We studied the dynamic changes of soil erodibility during the process of converting farmland to forest in typical black soil region by measuring and analyzing the characters of soil water-stable aggregates and soil erodibility factor K value from topsoil (0-10 cm) of different de-farming years.With the increasing age of conversion of farmland to forest , the content of water-stable aggregates was more than 0.25 mm ( the percentage of aggregates ) , the content of water-stable aggregates was more than 1.0 mm, and the mean weight diameter of water-stable aggregates from topsoil were increased , while the percent-age of aggregate disruption was more than 0.25 mm, mean weight soil specific area and soil erodibility factor K value were decreased .The change was more significant within 11-year-old reforestation , and gradually reached a stable state after 36 years old.The degree of topsoil aggregates was enhanced gradually , and the soil erodibility was decreased during the process of converting farmland to forest .After 36-year converting farmland to forest , soil anti-erodibility could be reached a certain level, and soil quality was improved to maintain a relatively stable state .By the analysis of correlation , K values were closely correlated with mean weight soil specific area , fractal dimension , mean weight diameter of soil water-stable aggregates, the mass fraction of water-stable aggregates at size >0.25 mm and >1.0 mm (p1.0 mm was more closely correlated with K than that at size >0.25 mm (p<0.01).Therefore, the soil erodibility factor can be taken as a sensitive indicator to assess soil erodibility of black soil .%以不同退耕年限林地表层土壤（0～10 cm）为研究对象，对土壤水稳性团聚体特征及可蚀性因子（ K）测定与分析，探讨东北典型黑土区退耕还林过程中表层土壤可蚀性的动态变化。结果表明：随退耕年限的增加，表层土壤水稳性团聚体粒径＞0．25 mm团聚体质量分数（团聚体比例）、粒径＞1．00 mm团聚体质量分数和平均质量直径逐渐增大，团聚体破坏率、平均质量比表面积和土壤可蚀性因子K值逐渐降低，且在前11 a内变化最显著，退耕36 a后呈不明显波动。退耕还林过程中，表层土壤团聚度逐渐增强，土壤可蚀性降低。退耕36 a后，土壤抗侵蚀能力达到一定水平，土壤质量得到改善，并维持相对稳定的状态。水稳性团聚体平均质量比表面积、分形维数、平均质量直径和粒径＞0．25、＞1．00 mm团聚体质量分数，均与土壤可蚀性因子K值呈显著相关（ p＜0．05）；其中，水稳性团聚体粒径＞1．00 mm团聚体质量分数比粒径＞0．25 mm团聚体质量分数与K值的相关性更为密切（p＜0．01），是反映黑土土壤可蚀性的敏感指标。