| Relationship of interaction between forest and water is the key topic of forest hydrology. As an effectual system for water conservation forest(WCF), It is not only different in composition and structure but also uniform in spatial configuration, which directly lead to difference and coordination existed in hydrology-ecology function of WCF. On the basis of studying water ecological characteristics (drought-tolerance law, transpiration law, value & resilience of water potential( wp), water utilization Tate(WUE))of 10 establishing community species and partner in Qilian Mountains, the capability of adjusting water content equilibrium and affection on composition and water transmission of forest eco-system as well as conservation function have been explained firstly, then the hydrological process of different interfaces(canopy layer, litter layer and soil layer) for vegetations and characteristics for water conservation have been analyzed .Conclusions are as follows:(1) As establishing community species of zonal vegetations, there are high drought-tolerance both Picea crassifolia and Sabina przewalskii, the former is characterized with water-economy and high drought-tolerance with high wp and water content ,high transpiration rate(rr) and WUE as well as perfect "first defense" of stoma, which resist water deficiency menace by delaying dehydration for sub-high wp. The latter is characterized with water-consumptive and low drought-tolerance with low wp and WUE as well as resist water deficiency menace by delaying dehydration for sub-low wp, although growing in bad water habitat(sunny slope) , it could consume lots of water when water supplying sufficiently and then severing soil water deficiency.(2) Populus cathyana and Betula albosinensis are characterized with water-economy and less drought-tolerance with mid value & resilience of wp, low Tr and high WUE. Meanwhile, they all have stronger cold-tolerance and high growth and depend upon moisture strongly so as to resist water deficiency menace by delaying dehydration for high wp.(3) Although there are good distribution in Qilian Mountains as establishing community species of mid-low-mountain shrubs, both Potentilla fruticosa L and Spiraea salicifolia L have less drought-tolerance and low value & resilience of wp so as to resist water deficiency menace by delaying dehydration for low wp. The former is characterized with mid water consumptive and the latter is characterized with high water consumptive.(4) Shrubs composed with 4 Rhododendrons , including Rhododendron thymifolium Maxim , Rhododendron capitatum Maxim > Rhododendron anthopogonoides Maxim and Rhododendronprzewalskii Maxim, which play a key role of stabilization in regional eco-system. Rhododendrons are characterized with evergreen-leather-leaf , alpine-cold habitat, high value & resilience of wp, mid drought-tolerance as well as low Tr and WUE. Rhododendron thymifolium Maxim is characterized with mid water consumptive and high drought-tolerance, and the others are characterized with water-economy and high drought-tolerance. Rhododendrons delay dehydration with high(or sub-high) wp except for Rhododendron anthopogonoides Maxim which with low wp.(5) The average canopy interception rate(Cir) of Picea crassifolia while canopy density( Cd) are less than 1.0 are 19.36%-23.96% and up to 25.67% when the Cd tend to 1.0, all less than 28.95% for Sabina przewalskii. The canopy interception amounts can be evaluated by modelI=a(1-e-PC ) + bPC which including canopy density factor C , here parameter a meansabsorption capacity and equal to 1.3627mm, parameter b means ratio of evaporation to precipitation and equal to 0.1835, stable Cir of Picea crassifolia equal to 20.4% by computing when Cd equal to 1.0. The average stem flow rate equal to 0.0182% and allocating little because of special biological characteristics of canopy.(6) The storage, natural water content and saturated water content of forest litters have ranked from great to little in moss- Picea crassifolia , alpine shrubs, shrub-Picea c...
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