Abstract: The transpiration is related closely to irradiance and soil water, and generally, it is that the rate of transpiration is increased with raising the irradiance and the soil water contant.Therefore, to lighten injuring on physiology as transpiration seriously, to increase the rate of survivor and to promote growing, it is necessary to adopt measure as avoiding violentir-radiance of the saplings when the soil is short of water.The soil water content as 10%< SWC <15%is beneficial to limit transpiration and to improve water use efficiency.