Influence of dry-hot valley on social economy
According to the experience of vegetation restoration in the dry-hot valley area for many years, it is considered that the dry-hot valley belongs to the dry-hot type of tropical climate in northern China and has the essential climatic characteristics of seasonal drought. In the selection of suitable tree species for vegetation restoration, the similar areas of tree species introduction should be tropical areas with obvious seasonal drought except native tree species.
At the same time, the vegetation restoration in this area should be based on sparse trees and shrubs. By artificially promoting vegetation restoration and making full use of abundant natural precipitation resources in rainy season, forest vegetation dominated by trees can be restored in some areas of dry-hot valley, and sparse trees, shrubs and grasses can be restored in certain areas.
Disaster and governance
Evolution of fragile ecological environment in dry-hot valley and its response to human activities.
The hot and dry climate in the dry-hot valley is the result of the "wind-burning" action far away from the ocean and mountains and valleys. Since the Quaternary, due to the uplift of the plateau and the deepening of the valley, the "wind burning" effect has been gradually strengthened, and the climate in the dry-hot valley has become increasingly dry and hot. The natural evolution of vegetation in dry-hot valley is quite slow, lagging behind the climate evolution, and the destruction of vegetation by human beings has accelerated the evolution of vegetation.
However, in recent 50 years, due to the large-scale irrigation of the land in the dry-hot valley and plain, the precipitation has increased, the temperature has decreased, and the evaporation has decreased, and the climate has developed in a benign direction conducive to human survival and resource utilization. This study provides an important scientific basis for the development and management of degraded ecological environment in dry-hot valley.
Sediment sources in the upper reaches of the Yangtze River, through the comparative analysis of sediment sources in Jialing River and Jinsha River, two important sediment-producing rivers in the upper reaches of the Yangtze River, it is found that the terrain fluctuation in Jialing River basin is small, and the sediment reduced by vegetation restoration and soil erosion control is enough to offset the sediment increased by engineering construction, and the precipitation is less, so the sediment transport has decreased obviously since the 1990s.
The topography of the downstream sediment-laden area fluctuates greatly, and the sediment increase of engineering construction is far greater than the sediment reduction of vegetation restoration and soil erosion control. Since 1980s, the sediment discharge of Jinsha River has been on the rise.