Study on the evapotranspiration simulation of sub-alpine forest area in Gongga Mountain

The Penman-monteith formula is applied to simulate the dynamic of evapotranspiration for naked land,Abies fabri forest and shrub-grass areas.The simulated results show that net radiation,air temperature and vegetation types are the predominant factors to control the dynamic of evapotranspiration.The evapotranspiration process modeled for naked land is similar to the observed evaporation of water surface.The higher values of evapotranspiration appear in April and September respectively owing to more sunshine and lower air humidity,while the lower values appear in July and August for great deal of rainy days.The simulated values of evapotranspiration of forest and shrubgrass areas are higher in growth period,or lower in non-growth period than that of naked land surface.The difference between these two kinds of land surface varies by ±25%.The simalated results show that the modified Penman-Monteith formula can be used satisfactorily in the hydrological cycle analysis for mountain regions with forest coverage.