Studies On The Hydrological Effects With Different Forest Types In Badong County In The Three-Gorge Reservoir Area

With the investigation data on the climate characteristics and forest resources of Badong county in the Three-Gorge Reservoir Area, the hydrological course of the forest, which includes rainfall interception, water absorption for litter-form and soil., were studied carefully by means of dividing the hydrological course.Based on rainfall data of Badong from 1993 to 2003, the characters of rainfall were analysed. It showed that the annual rainfall is abundant (the annual average rainfall is 978.58mm) and various. The annual rainfall is mainly distributed from May to August, in which there are many moderate rains, downfalls, rainstorms.There are five forest types in the research areas, which contains the mixed forest of conifers and broad-leaved trees, the forest of Pinus massoniana Lamb, the forest of broad-leaved trees, the mixed forest of conifers and the forest of Cupressus funebris Endl.. The hydrological effects with five forest types were studied in the point of static and dynamic view. It showed that the water holding capacity of branches and leaves of broad-leaved trees is bigger than that of coniferous trees in arbor layer. Also, the capacity of each layer of shrub, herbage and moss layer is very big, especially moss layer (314.61%), they all play very important part in absorbing rainfall. The rainfall redistribution characteristics of canopy interception for five forest types in Badong county were studied by using fixed standard sample method. The results suggested that in different forest types, the rainfall redistribution characteristics of canopy in growing period were different. Throughfall and stemflow have a positive-linear relationship with rainfall, and the percentage of throughfall and stemflow increase with rainfall during the initial rainfall period, but keep stable in the later stage. There is relationship between the rainfall and Canopy interception as a power regression. The interception increases with rainfall, and the percentage of interception decreases with rainfall contrarily, dropping down quickly during the initial rainfall period, then slowly, and finally reaching the canopy-saturated state. The average canopy interception of five forest types is 48.64mm; the average percentage of canopy interception of five forest types is 20.95%; Not only the canopy interception but also the percentage of canopy interception of five forest types were different, in the order from the largest to the least: the mixed forest of conifers and broad-leaved trees, the forest of Pinus massoniana Lamb, the forest of broad-leaved trees, the mixed forest of conifers and the forest of Cupressus funebris Endl..Through the survey of the amount of forest litter form and experiments of water holding characteristics in five kinds of forest stands in the Lianxia River Watershed in theresearch areas, some characteristics parameter of forest hydrology were gained, such as the different kinds of forest litter form amount, the maximum water capacity and the water absorbing speed. The results showed that the amount of the litter form is in the descending order of the mixed forest of conifers and broad-leaved trees, the forest of Cupressus funebris Endl., the forest of Pinus massoniana Lamb., the mixed forest of conifers and the forest of broad-leaved trees. The maximum water capacity of the undecomposed litter form ranges from the forest of Cupressus funebris Endl. 1.98mm, the forest of conifers 1.83 mm, the mixed forest of conifers and broad-leaved trees 1.27 mm, the forest of broad-leaved trees 1.21 mm and the forest of Pinus massoniana Lamb. 1.1 Omm in the decreasing order. The maximum water capacity of the half-decomposed litter form follows the descending order from the forest of Pinus massoniana Lamb. 2.30 mm, the mixed forest of conifers and broad-leaved trees 2.28 mm, the forest of Cupressus funebris Endl. 2.21 mm, the mixed forest of conifers 1.76 mm and the forest of broad-leaved trees 1.49 mm. In this watershed, the water holding capacity of the litter form of the forest of Cupressus funebris Endl. is the biggest, and conifers, mixed forest of conifers and broad-leaved trees, forest of Pinus massoniana Lamb, and forest of broad-leaved trees follow the previous in order. When only litter form covers soil and there was no water infiltration and no water running off from ground surface, the maximum rainfall amount and the maximum rainfall intensity in different forest stands are 4.19mm and 1.96mm/h for the forest of Cupressus funebris Endl., 3.59mm and 2.15mm/h for the mixed forest of conifers, 3.55mm and 2.54mm/h for the mixed forest of conifers and broad-leaved trees, 2.70mm and 1.84mm/h for the forest of broad-leaved trees and 3.40mm and 1.45mm/h for the forest of Pinus massoniana Lamb respectively.The investigation indicated that different forest soil has different characteristics. The characteristics of forest soil changes regularly with the depth. The total water held in forest soil, which is mainly affected by soil's total porosity, is cypresse, mixed conifers, mixed conifers and broad-leaved trees, masson pine, broad-leaved trees forest in the decreasing order.On the base of the above analysis and the comparison of the hydrological effect of five forest types, it showed that the integrated capacity of adjusting hydrological effect is the forest of Cupressus funebris Endl., the mixed forest of conifers and broad-leaved trees, the mixed forest of conifers, the forest of broad-leaved trees and the forest of Pinus massoniana Lamb in the decreasing order.