| The relationship between forest and water is of great importance in hydrology. In this paper, we choosed five typical vegetation types (mixed forest of conifers and broad-leaved trees, forest of Pinus massoniana, broad-leaved forest, Castanea mollissima forest and cropland) in Lanlingxi small watershed in the Three Gorges Reservoir Area. Influence of vegetation type change on hydrological process and water quality change in different hierarchy including rainfall, throughfall, stemflow, litterthrough, runoff and subsurface flow had been studied. The water quality of different hiberarchy had been evaluated by using method of general index. The results showed:(1)There was a significant linear correlation between throughfall and precipitation in different forest types, and the rate of throughfall of forest of Pinus massoniana, mixed forest of conifers and broad-leaved trees, broad-leaved forest and Castanea mollissima forest were 81.71%, 80.15%, 78.55%, and 77.58%. There was a significant linear correlation between stemflow and precipitation, and the proportion of stemflow of forest of Pinus massoniana, mixed forest of conifers and broad-leaved trees, and broad-leaved forest were 0.25%, 0.48%, and 1.32% respectively. But the values were very low. The relationship between canopy interception and precipitation was a significant power function, and the rate of canopy interception of forest of Pinus massoniana, mixed forest of conifers and broad-leaved trees, broad-leaved forest and Castanea mollissima forest reached 18.04%, 19.37%, 20.13%, and 22.42% respectively.(2)The amounts of litter of different forests were different. The amount of litter of the three forest types(broad-leaved forest, forest of Pinus massoniana, mixed forest of conifers and broad-leaved trees) in per unit area were 16.88 t·hm-2, 13.24 t·hm-2 and 6.88 t·hm-2. The amount of litter of mixed forest of conifers and broad-leaved trees was the lowest in the three forest types, because artificial disturbance make a serious loss to litter. The water-holding capacity of different was different. The maximum water-holding capacity of the three forest types in per unit weight was: mixed forest of conifers and broad-leaved trees (2863.g·kg-1)＞broad-leaved forest (2696.9g·kg-1)＞forest of Pinus massoniana (1796.0g·kg-1). The relationship between the water capacity (water-losing capacity) of litter production and immersion time (water-losing time) was a logarithm function. The relationship of the water absorption speed (water losing speed) of litter production and immersion time (water-losing time) was a power function. (3)The order of soil bulk density of the five vegetation types was: Castanea mollissima forest(1.865g·cm-3)＞forest of Pinus massoniana (1.815g·cm-3)＞broad-leaved forest (1.7965g·cm-3)＞mixed forest of conifers and broad-leaved trees (1.53 g·cm-3)＞cropland (1.46g·cm-3). The soil porosity sequence of the five vegetation types was: mixed forest of conifers and broad-leaved trees(44.345%)＞cropland(44.3%)＞broad-leaved forest(33.7%)＞forest of Pinus massoniana(30.4%)＞Castanea mollissima forest(29.7%). The efficient water storage capacity was: mixed forest of conifers and broad-leaved trees (307.30t·hm-2)＞Castanea mollissima forest (305.80t·hm-2)＞cropland (274.95t·hm-2)＞forest of Pinus massoniana (261.80t·hm-2)＞broad-leaved forest (178.00t·hm-2). The stable percolation rate was 0.03 mm·min-1 to 2.96 mm·min-1. The stable percolation rate of broad-leaved forest and forest of Pinus massonian reached 2.96 mm·min-1, which was highest in A layer; and of cropland was lowest as 0.96 mm·min-1. In B layer, the stable percolation rate of cropland was 0.97mm·min-1, that is highest; forest of Pinus massonian and mixed forest of conifers and broad-leaved trees were lowest as 0.03 mm·min-1.(4)The concentration of chemical constituents of different water was variational from precipitation to subsurface flow in different vegetation types. After precipitation penetrate through vegetation, The TURB and EC value enhanced, but content of DO dropped. Comparing with rain outside forest, the pH value of throughfall, stemflow in different forest was decreased, which had shown the tendency of water quality acidification. In comparison with precipitation, the pH value of runoff of mixed forest of conifers and broad-leaved trees, forest of Pinus massoniana and Castanea mollissima forest was increased, which buffered water quality acidification.The concentrations of NH3-N in runoff and subsurface flow of mixed forest of conifers and broad-leaved trees and Castanea mollissima forest were lower than precipitation. Subsurface flow of forest of Pinus massoniana and broad-leaved forest and runoff of cropland were lower than precipitation, too. Compared with in precipitation, the concentrations of NH3-N in different forest hierarchy were increased. It displayed that surface and inner soil had effect of purification for NH3-N.After rainfall through mixed forest of conifers and broad-leaved trees, the concentrations of Ca, Mg, K, Na, P of the water of different forest hierarchy were higher than rain outside forest. The contents of Mg and K in water of every forest hierarchy in forest of Pinus massoniana were higher than rainfall. Through Castanea mollissima forest, the concentrations of Ca, K, Na, P had been increased. The contents of K, Na, P, Fe in the runoff of cropland all increased in some degree. The content of N of the runoff and subsurface flow in the two types forest was lower than rainfall (mixed forest of conifers and broad-leaved trees, Castanea mollissima forest), which illustrated the two levels have better purification ability to total N.(5)The general evaluation of water quality of precipitation during monitoring in Lanlingxi small watershed reachedⅢdegree, which showed slightly pollution. The water quality of throughfall and stemflow of oakery forest in mixed forest of conifers and broad-leaved trees and broad-leaved forest come up toⅣdegree, so throughfall in forest of Pinus massoniana and Castanea moUissima forest were; The water quality of stemflow of Pinus massoniana in mixed forest of conifers and broad-leaved trees and forest Pinus massoniana and litterthrough in mixed forest of conifers and broad-leaved trees and forest broad-leaved come up toⅤdegree; The subsurface flow in mixed forest of conifers and broad-leaved trees and runoff and subsurface flow in Castanea mollissima forest reachedⅡdegree, which had better purification effect on water. Except forest of Pinus massoniana, the water quality of runoff or subsurface flow come up toⅢdegree in broad-leaved forest and cropland, and the values of the general index M were lower than rainfall which showed the purification ability to the rainfall, but the effect was not significant. Owing to the human interference, the lower rate of coverage and the tree's features itself (rough bark, secreting resin, etc.) in forest of Pinus massoniana, the water quality of subsurface flow only come up toⅣdegree.
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