干热河谷的形成特征与植被恢复相关问题探析

通过对西南地区干热河谷的形成过程及其相关的气候、土壤、植被和微生物共生系统进行分析，探讨进一步实现森林重建的相关问题。笔者认为：干热河谷现有植被是植物与当地环境经历数百万年的协同进化形成的，地质历史上和人类历史上记载的植被类型不能作为当前植被恢复的终极目标。干热河谷植被恢复目标树种和生态效果的确定，应与当地的生态容量相适应，采取宜林则林、宜灌则灌、宜草则草的策略，对于极端困难地段不应盲目追求恢复森林。植被恢复区所处的生物气候条件和土壤地质条件决定了该区域的生态容量，对于不同树种有所差异，一旦超出了该树种相对应的生态承载力，不管造林成活率和造林保存率有多高，随着林分郁闭度的提高，树木个体的竞争不断加剧，有些树木会逐渐死亡，树种特性和生态容量将决定最终形成的森林生物量和林分密度。适地适树是植被工作的基本原则，抗旱保水技术只能帮助树木避免短期的气候波动所造成的土壤干旱对苗木的胁迫，是适地适树基础上的辅助措施，并不能保证在不适宜造林的地区实现森林恢复。因此，植被恢复的验收标准应该根据不同树种和不同地区的实际情况有所调整。

Discussion on the Formation Characteristics of Dry-Hot Valley and Related Problems of Revegetation

The paper analyzes the formation process of the dry-hot valley in Southwest China and its related characteristics of climate, soil, vegetation and microbial symbiosis system, then explore the issues related to further vegetation restoration. The author hold the view that the existing vegetation in the dry-hot valley is formed by the co-evolution of plants and local environment for millions of years. The vegetation types recorded in geological history and human history may not be regarded as the ultimate goal of vegetation restoration. The target tree species and ecological effect of vegetation restoration in dry and hot valley should be determined according to the local ecological capacity. Some area may suitable for forest, some suitable for shrub, some may only suitable for grass. For extremely difficult areas, it should not blindly pursue forest restoration. The ecological capacity of the area is determined by the bioclimatic and soil geological conditions of the vegetation restoration area. There are differences for different tree species. Once the ecological carrying capacity of the tree species is exceeded, no matter how high the survival rate and conservation rate of afforestation are, with the increase of forest canopy density, the competition of individual trees is increasing, some trees will gradually die, and the characteristics of tree species and ecological capacity will determine the biomass and stand density of the final formed forest. Tree adaptation is the basic principles of vegetation restoration. The technology of drought resistance and water conservation can only help trees to avoid the stress of soil drought on seedlings caused by short-term climate fluctuation. It is an auxiliary measure on the basis of tree adaptation, and may not guarantee the realization of forest restoration in the area unsuitable for afforestation. Therefore, the acceptance standard of vegetation restoration should be adjusted according to the actual situation of different tree species and different regions.