Climatic changes on alpine grassland of the Three-Rivers Resource Region andtheir potential impacts on grass yield

With the method of path analysis, study was made on the changes of climate and grass yield on alpine grassland of Xinghai County, located in Three-Rivers Source Region of Qinghai Province. In the past 14 years, annual grass yield increased significantly, and showed a significant positive correlation with the accumulated ≥0 ℃ temperatures and the precipitation in growing seasons. At heading-flowering stage, atmospheric temperature and precipitation had greater impacts on grass yield. At maturing-Withering stage, the accumulated ≥0 ℃ temperatures had some impacts on grass yield, at flowering-maturing stage, average wind speeds had negative impacts on grass yield. In the past 14 years, annual atmospheric temperatures and precipitation kept increasing significantly. At heading-flowering stage, atmospheric temperature and precipitation increased significantly, at maturing-Withering stage, the accumulated ≥0 ℃ temperature increased significantly, at flowering-maturing stage, average wind speeds decreased significantly. During late growing period of grasses, improving of heat and moisture conditions and lowering of wind speed were favorable for grass yield. When atmospheric temperature and precipitation continue increasing, evaporation of soil may weaken, and such conditions will make grass yield promoted.