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为了揭示森林植被水文效应的动态变化过程,将简化的简单生物圈模型与动态植被模型和流域地形指数水文模型相耦合进行长江上游梭磨河流域植被及其水文效应的动态模拟。结果表明:植被覆盖和叶面积指数的增加使植被蒸腾和冠层截留蒸发增加而使土壤蒸发减小,植被的水文效应取决于蒸发分量中这两个相反方向变化的净效应。流域主要由草地和灌木覆盖时流域总蒸发大于裸地和林地。与裸地相比较,当单位叶面积指数截留能力取值0.1mm时,森林减小了流域总蒸发,但当单位叶面积指数截留能力取值0.2mm时,森林增加了流域总蒸发。森林的水文效应对冠层截留能力敏感,冠层截留能力存在一个控制森林水文效应从减小总蒸发变为增加总蒸发的转折点。植被的水文效应是随时间变化的,对于给定的植被类型其叶面积指数是决定其水文效应的关键因子。
In order to reveal the dynamic process of hydrological effects in forest vegetation, the simplified simple biosphere model was coupled with the dynamic vegetation model and hydrological model of watershed topographic index to simulate the vegetation and its hydrological effects in the Shumuma River basin in the upper reaches of the Yangtze River. The results showed that the increase of vegetation cover and leaf area index led to the decrease of soil evaporation due to the increase of vegetation transpiration and canopy interception evaporation. The hydrological effects of vegetation depend on the net effect of the two opposite directions of evaporation component. The total basin evaporation is larger than bare land and woodland when covered mainly by grassland and shrub. Compared with the bare land, when the unit leaf area index cutoff value is 0.1mm, the forest reduces the total evaporation in the basin, but when the unit leaf area index cutoff value is 0.2mm, the forest increases the total evaporation in the basin. The hydrological effects of forests are sensitive to canopy interception, and there is a turning point for controlling forest hydrological effects from reducing total evaporation to increasing total evaporation. The hydrological effects of vegetation vary with time and its leaf area index is a key factor determining the hydrological effect for a given vegetation type.