南亚热带水土流失地区人工加速植被演替过程

水土流失地区植被在自然条件下从阳生草本到乔灌草复合植被的演替过程常常需要很长的时间，选取适当树种人工造林可以省略先锋物种强阳生草本的发育时间，提早诱发灌木和草本植物发育，大大加速植被恢复演替过程。通过对广东惠州市惠阳区上杨试验站等南亚热带典型水土流失地区的研究发现：自然封育状态下，水土流失地区植被恢复和演替缓慢，25。后植被覆盖度只有35％，且主要以阳生性耐贫瘠的灌木及草本为主，土壤侵蚀仍然比较严重。选择大叶相思树人工造林加速了植被演替进程，控制了水土流失，12a左右植被覆盖度就达90％左右。造林23a左右，林地遮蔽涵养水分和控制侵蚀作用下迅速生长多种当地物种，形成了乔、灌、草、藤、竹多层复合植被。在南亚热带季风气候地区，自然封育状态下严重水土流失区植被恢复至较稳定的次生林阶段需要60a左右的时间；人工造林加速植被演替只需要20a。植树造林是该地区植被恢复发育及控制水土流失的有效措施。

Vegetation succession process induced by reforestation in erosion area

Reforestation is one of the most important and efficient measures of water and soil conservation. Based on field investigation at the Shangyang Soil Conservation and Reforestation Station in Huizhou, Guangdong Province, China, vegetation development, the vegetation succession process, and soil erosion variation are studied in this paper. The regional vegetation consists mainly of monsoon evergreen broad-leaved forest. The area was deforested and became a bare hilly area with extremely high soil erosion in the 1960s and 1970s. Then the area was closed for vegetation recovery. Under natural conditions the vegetation development and the succession process are slow. Soil erosion, strong sunshine, and evaporation slow vegetation development. About 25 years later, the vegetation cover merely reached 35 % or so. The dominating vegetation types were heliophilous herbages and shrubs, which formed a poorly developed shrub-herbage community. The erosion is still high. On the other hand, reforestation with selected species of trees dramatically sped up the vegetation succession process. About 12 years after reforestation, the vegetation cover of the artifical Acacia auriculaeformis forest at the Shangyang Station reached 90% and erosion was on controlled. After 23 years, understory vegetation consisting of local species has developed in the artificial forest. The planted trees and naturally developing plants, shrubs, bamboo, trees, and liana formed a complicated vegetation community with three layers. It takes about 60 years for the vegetation to progress from bare land to second growth forest under natural conditions. Reforestation may speed up the vegetation succession process. The time may be reduced to 20 years. Reforestation is an effective measure of vegetation restoration and erosion control in this area.