Study On Water Conservation Function Of The Picea Crossifolia In Central Of Qilian Mountains

The study combines with the experimental observation, in the size of the catchments, studying the water process and mechanism and discussing the theory and practice problem to resolve the relationship between forest and water from lots of aspects, such as precipitation, water transmission in canopy layer, litter layer, water dynamic in forest soil layer, etc. then, we obtain the following achievements:(1) The precipitation period could be divided into rainy and dry season due to the variation. The precipitation in the rainy season (from May to Oct.) approximately accounts for 87.2%; while that in the dry season (from Nov. to Apr.) is few, which only accounts for 12.8%. there are two forms of precipitation: snowfall and rainfall, the snowfall accounts for 27.8% and the rainfall is 72.2%. Snow is the unique'solid reservoir of forest in Qilian Mountains; it plays good role to the drought in spring that occurred in the middle and lower reaches of rivers originated from the Qilian Mountains.(2) The canopy interception generally increases with precipitation, but the increase is limited, when the interception to the maximum extent interception after interception is no longer with precipitation increasing, sometimes decreasing. The canopy interception rate changes between 22.6%~34.5%,averaging at 29.4%,general,the canopy interception rate increases with the level of decreased rainfall.the canopy interception of five forest types change from big to small are Picea crossifolia,Wet shrubs,Sabina przewalskii,Dry shrubs,Ssloping pasture.(3) The effective moisture of moss and litter layer are Wet shrubs(152.65mm)>the Picea crossifolia(150.04)>Dry shrubs(36.12mm)>Sabina przewalskii(11.49mm)> Sloping pasture.(4) The soil water in the experimental catchments has the obvious spatial and temporal difference, the shadow slope contains more water than in the sunny slope; the containing water of the soil thaw layer represents the trend of decreasing with the increasing of soil depth. compared with the soil that contains less water, the vertical variation of the more one is small. the influencing factors of soil water seasonal changes are quite complex, in which the precipitation and plants are two most important ones; the soil water containing amount from the surface to the deep increases with the rising altitude, the hectometer average increasing rate is 14.15%, the water containing amount of frozenIt will provide a scientific basis for the eco-construction planning and the choice of project model of the Qilian Mountains area by the research of forest ecosystem water conservation and distribution pattern.