Abstract:Based on field measurement, the CoupModel (Coupled heat and mass transfer model for soil-plant-atmosphere system) was applied to simulate water balance in three kinds of vegetation types, including broadleaved forest (Schima superba and Lithocarpus glaber), coniferous forest (Cunninghamia lanceolata and Pinus massoniana) and farmland (Zea mays) in Three Gorges Reservoir Area of China. The results showed that the simulated values of soil moisture were fairly consistent with measured ones and the determination coefficient ( R2 ) were 0.80 to 0.91. Evapotranspiration was main output of water balance with the percentage up to 61%, and the figures were ranked as follows: broad-leaved forest (720 mm/a)>coniferous forest (700 mm/a) > farmland (601 mm/a). Annual simulated deep percolation decreased by 60 mm for broad-leaved forest and 47 mm for coniferous forest compared with that for farmland (452 mm/a), and it was even greater in wet year. For broad-leaved forestland, water consumption was more than income during the experimental period, which was the main reason causing soil water deficit. The water balance of farmland was characterized by moisture surplus, while spring and autumn drought occurred in forestlands. There was obvious difference between forestland and farmland for water conditions. Model results indicated that the vegetation species significantly influenced the magnitude of water balance components, which called for further attention to the selection of tree-species when planning future afforestation projects. Forest tending should also be applied scientifically during the practice of vegetation restoration.
