Lai Yongqi, Liao Shengxi, Liu Dachang, Liu Jun, Su Jianrong and Zhang Yanping
The dry and hot valley climatic type occurs mainly in the southwest provinces of Yunnan, Sichuan and Guangxi. In Yunnan, this climatic type covers 13 000 km², between latitudes 22.5°-28.0° N, and makes up 3.4% of the area of the province (Yang 1992). As the name suggests, it is a hot, dry climate providing harsh growing conditions for plants and the aridity is a critical constraint to tree planting and plantation establishment.
Little forest vegetation remains in areas with these climatic conditions. Forest land is often seriously degraded, has had its vegetation cover reduced to sparse shrubs or even bare...