A Study on Hydrologic Function of Canopy of Picea Crassifolia in Qilian Mountains

Based on the long-term location research of forest eco-system in Qilian Mountains, using theory of mathematical statistics and mathematical model to analyze data, this paper formulizes quantitative and qualitative changes of rainfall caused by canopy of Picea crassifolia, simulates interception model by canopy of Picea crassifolia. The results show that penetration rainfall inside forest increases with total rainfall outside of forest, the relationship between them is conform to linearity, To certain extent, intercepted rainfall by canopy also increases with total rainfall.The average rainfall intercepted rate by canopy of Picea crassifolia is 29.4%, it diminishes with the increase of rainfall and rainfall intensity and increases with the increase of closing degree of canopy. The average intercepted rate of rainfall by canopy is about 10%～30% less than snow. Measuring average value is 11.7% less. The gross ion content in penetration rainfall under canopy is 2 times more than the outside because the washing. The input quantity of nutrient content by the canopy washing is 61.042 4 kg·hm -2 ·a -1 .