南方花岗岩区不同侵蚀土壤治理效果的研究

STUDY ON SOIL CONSERVATION EFFECT FOR DIFFERENT ERODED SOILS IN GRANITE REGION OF SOUTH CHINA

花岗岩红色风化壳广泛分布于我国南方山地丘陵区。其中的红色粘土层质地粘重且被铁铝氧化物胶结,与其下部的砂土碎屑层相比具有很强的抗蚀能力,对该区侵蚀的发展和治理具有重要意义。本研究通过对保留红色粘土层和砂石碎屑层裸露两种类型的侵蚀土壤在治理过程中保持措施的选择、植被和土壤肥力的恢复与土壤发育特点进行对比,说明了花岗岩区的侵蚀土壤在保留红土层时,土壤退化的程度轻,治理较容易,植被和土壤生产力的恢复较快;一旦红土层被侵蚀贻尽,侵蚀的速度加快,治理过程中植被和土壤生产力的恢复也慢。

The widely distributed granite weathering crust in south China is generally composed of four layers: soil organic layer (20—50 cm), red clay layer (1—5 m), sandy layer (5—10 m) and fragmental layer (10—20 m), in which the red clay layer is firmly cemented by clay and Fe-Al oxides and thus has a higher anti-erodibility than the underlying sandy and fragmental layers. Therefore, soil erosion and conservation are quite different whether eroded soil possesses a red clay layer or not. By comparing conservation measures, restoration of vegetation and soil fertility, and soil development of the two types of eroded soils with conservation measures taken for 22 years, the present study reveals that when eroded soil possesses a red clay layer, soil degradation and erosion are not so serious. Good vegetation and high soil fertility can be restored in a short time by densely planting in combination with a few mechanical measures such as squamose hole and bench terrace when necessary Once the sandy or fragmental layer exposed by progressive sheet or gully erosion, soil erosion and degradation would become very severe for the erodible infertile sandy soil, and soil conservation therefore would be very difficult. It needs much longer time to restore the soil fertility and vegetation even though grasses, shrubs and trees are systematically planted in combination with various mechanical measures such as contour ridge, bench terrace and cheek dam.