气温变化对西南山区流域森林水文效应影响的模拟

为了揭示气温变化对西南山区流域森林水文效应的影响,用生物物理/动态植被模型SSiB4/TRIFFID与流域地形指数水文模型TOPMODEL的耦合模型SSiB4T/TRIFFID模拟了西南山区长江上游梭磨河流域森林水文效应对气温变化的响应,分析了气温变化对植被不同演替阶段的流域总径流和总蒸发以及冠层截流蒸发、植被蒸腾和土壤蒸发的影响。结果表明,（1）梭磨河流域森林（常绿针叶林）蒸腾与草和灌木差异小,森林蒸腾潜热比草和灌木仅高1~4 W.m-2,森林冠层截留蒸发高于草和灌木,但土壤蒸发明显低于草和灌木覆盖,森林覆盖流域总蒸发低于草和灌木覆盖甚至低于裸土蒸发,因此增加了流域总径流量,但森林增加径流的作用随土壤蒸发的减小而减小。（2）气温减小1℃将通过减小森林冠层截留蒸发和蒸腾而使森林增加流域总径流量的作用增加;相反,气温增加将增加森林冠层截留蒸发和蒸腾而使森林增加总径流量的作用减小。（3）当温度增加4℃,由于森林总蒸发较草和灌木明显增加,对于较高的土壤蒸发,森林增加总径流量的作用已不明显;对于较低的土壤蒸发,森林减小了流域总径流量。

Modeling the impacts of temperature changes on hydrological effects of forests in the mountain region of southwestern China at basin scale

In order to reveal the effects of temperature changes on hydrological effects of forests in the mountain region of southwestern China at basin scale,the coupled model SSiB4T/TRIFFID（Plant dynamic vegetation model TRIFFID and TOPMODEL are integrated into the land surface model SSiB4） is employed to conduct numerical simulations of the dynamic changes of vegetation and water balance of the Suomo Basin which is located in the upper reaches of the Yangtze River.The impacts of temperature on total runoff and evaporation（including canopy interception evaporation,soil evaporation and transpiration） in different vegetation succession periods are analyzed.The results show that in the Suomo Basin transpiration of forest（needleleaf-evergreen forest） is not significantly different with transpiration of grass and shrub,latent heat flux of forest transpiration is only 1-4 w.m-2higher than that of grass and shrub.Canopy interception evaporation of forest is higher than that of grass and shrub,however,the soil evaporation of forested land is much lower than that of grass and shrub land.Evaporation of forested land is less than that of grass and shrub land and even less than bare soil evaporation.The total evaporation of the basin is the lowest when the basin is covered by forests.As a result forests increase the total runoff of the basin.However such effect of forests will decrease with decrease of soil evaporation.The results also show that a decrease in temperature by 10C will enhance the effect of forests on the increase in the total runoff through decrease in evaporation of forest canopy interception and forest transpiration.On the contrary,an increase in temperature will result in an increase in evaporation of forest canopy interception and forest transpiration and reduce the effect of forests on the increase in the total runoff.The results indicate that temperature rises to 40C will cause that forests have no significant effects on the increase in runoff for the higher soil evaporation case and forests turn to reduce the total runoff for the lower soil evaporation case due to the more significant increase in forest evapotranspiration compared with the increase in grass or shrub evapotranspiration.