北川河流域退耕地植物群落土壤抗蚀性研究

EFFECT OF PLANT COMMUNITY ON ANTI-ERODIBILITY OF LAND UNDER REHABILITATION IN BEICHUANHE BASIN

土壤抗蚀性指土壤抵抗水的分散和悬浮的能力。国家退耕还林还草科技试验县———青海省大通县北川河流域的抗蚀性试验研究结果表明 ,用于衡量土壤抗蚀性的 12项指标 ,经过主成分变换后 ,能够反映特征根大部分信息 (85 .6 % )的主成分包括无机黏粒类、团聚类、无机胶粒类和水稳性团粒类 4大类。通过对 4个主成分进行聚类 ,北川河流域植物群落分为 3大类 ,其中抗蚀性最好的一类以天然林为主 ;抗蚀性居中的一类以退耕时间较长的人工林地为主 ;抗蚀性较差的一类以新退耕还林地为主。随着退耕时间的延伸 ,退耕地人工林的抗蚀性较耕地不断提高 ,而与当地天然次生林的抗蚀性愈来愈接近。以仿自然林为手段的退耕地人工林的营造是成功的 ,以土壤抗蚀性为基础 ,结合其他多方面的生态功能 。

Anti-erodibility refers to soil's ability to resist the dispersion and suspension caused by runoff. The study on anti-erodibility in the Beichuanhe Basin of Datong County, a national experimental site for conversion from cropland into forest land and grassland, shows that all the 12 anti-erodibility indexes can be divided into 4 categories, i.e. inorganic clay, aggregate, inorganic colloid and water-stable aggregate, capable of reflecting 85.6% of the information of the eigenvalues, by means of PCA. All the plant communities in the Beichuanhe Basin can be clustered into three kinds based on the four categories with the Hierachical Cluster Method. The first kind with good anti-erodibility mainly includes native forests, and the second kind with medium anti-erodibility is composed of artificial forests on rehabilitated lands of the early days, whereas the third with poor anti-erodibility is made up of newly established artificial forests in rehabilitated lands. The anti-erodibility of artificial forests is getting stronger and stronger as the forest ages, approaching that of native forests. It is successful to reafforest steep croplands in a natural way, and such artificial forests can play a good role in soil and water conservation based on anti-erodibility and other related eco-functions.