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.