西南地区的干热河谷及其森林培育(英文)

The dry-hot valleys and forestation in southwest china

干热河谷主要分布于长江、珠江、澜沧江、红河和怒江等国内和国际性河流的上游深切 河谷地段。本文对干热河谷形成的地理和气候原因进行了阐述，并通过引证大量文献，分析 了干热河谷植被的历史情况和现状。由于干热河谷地区的地质结构不稳定、土层浅薄、人口 膨胀、过度耕种，尤其长达半年的旱季等原因，导致该地区的生态环境处于极端的脆弱阶段 。当地的原始植被为常绿阔叶林和落叶阔叶林，但均遭到严重的破坏。现有植被为次生的稀 树草坡和肉质化刺灌木。由于干热河谷的植被情况直接影响河流水体的质量，因此河谷内的 植被恢复和水土保持就成为流域治理的最重要的任务。目前已经开展了一系列的有关造林技 术的前期研究项目，但大规模的造林培育工程尚难以开展。

The dry-hot valleys (DHV) are located mainly in the deeply incised v alleys along the upper streams of several international and domestically rivers, like Yangtz, Zhu, Lanchang, Hong, and Nu rivers. This paper briefly described t he reasons of formation of DHV from view of climate and geographical conditions, and by referring to great deal of documents, analyzed the historical case and p resent status of the vegetations in DHV. The environment in DHV is facing the se rious vulnerable period in the history due to its nature situation of half-year dry period, fragile geological structure and shallow soil, and its social situat ion of over dense population and over farming. The primary vegetation is broad l eaf forest and it was denuded in the history. The current local vegetation is th e degraded secondary vegetation: savanna and succulent thorny shrub. Since the e nvironmental situation in valley influenced directly the water body of river, th e soil erosion control and re-vegetation in DHV is the most urgent task in the p rocess of environmental harness along the rivers. Quite a few pilot research pro jects have been carried out.on demonstrating new silviculture techniques for re- vegetation in DHV, but there still exist great difficulties in carrying out larg e-scale afforestation engineering.