Study On Water Conservation Function Of Ecosystem Of Picea Crassifolia Forest In Qilian Mountains

Forest ecosystem has more channels of complex material circulation and energy conversion, it plays an important role in Geosphere-Biosphere biogeochemical cycles. The study was based on the long-term orientation research about the forest ecosystem of the Qilian Mountains, through the observation of Qilian Mountains in Picea crassifolia forest in hydrology, microclimate, soil etc, in water conservation analysis. The findings were showed that:1. The microclimate characteristics in Picea crassifolia forest of QilianMountains: The forest temperature was smaller 3.91℃than the outside of forest, the average annual temperature was lower 0.1℃than the outside. Relative humidity difference of forest and the outside is 8? percentage points. The forest rainfall intensity and precipitation significantly smaller than the outside, and was 60% of the outside precipitation.2. At an altitude gradient, precipitation had a dramatic change in a small basin of the transition zones one vegetation types within the other vegetation types in Picea crassifolia forest of Qilian Mountains.3. Precipitation distribution of Picea crassifolia forest ecosystem of Qilian Mountains .Characteristics of canopy interception: in a certain range, the general trend of the interception decreased with the increase of precipitation, the greater of the rainfall intensity, the smaller of the interception rate; and under the same rainfall intensity, interception and interception rate increased with the canopy density increased.The process of precipitation distribution of Picea crassifolia forest ecosystem in Qilian Mountains: the retention characteristics of canopy layer, moss litter and soil layer were similar . the process can be divided into three stages: With the increase of the rainfall. The first stage is retention stage, interception and interception rate increased with the increase of rainfall input. The second stage is penetration stage,interception accumulation increased than the first phase, but the rejection rate was decreased. The third stage is the saturation stage, interception reached to the maximum, and the retention rate was closed to zero.Frozen soil acted as impermeable layer and the water layer, runoff depth increased with permafrost inhibited water infiltration to deeper soil. At the same time permafrost can increase the runoff in the end of spring and early of summer, and reserve rainfall of summer, autumn and winter in the fall, finally, basin's water storage was increased.4. The composition of bryophyte and litter and the hydrological characteristics of Picea crassifolia forest in Qilian Mountains:The average thickness of Bryophyte and litter of the Picea crassifolia forest in Qilian Mountains was 8.2 cm; the rest of the decomposition components in the bryophyte and litter was accounted for 42.8%; semi-decomposed and decomposed components accounted for 23.8% and 33.4%; which components of litter, leaves 67%, branches 17%, fruits 16%.The Maximum water retention rate of Bryophyte and litter layer changed from 276.65% to 370.48%, the average was 322.53%, and the maximum water retention capacity was 3 times than its own dry weight . The maximum Water holding capacity varied from 7.6 to 29.1mm, the average was 18.4 mm.5. Soil physical properties and the hydrological characteristics of Picea crassifolia forest in Qilian Mountains:Compared the soil physical properties of Picea crassifolia forest with the sloping pasture's (comparison), the soil layers average bulk density of Picea crassifolia forest (0.764g/cm3) was less than the sloping pasture,s (1.231 g/cm3), the non-capillary porosity average (16.77%)of soil layers was less than sloping pasture (10.2%); in the soil surface, sloping pasture soil bulk density (1.45 g/cm3) was 3 times than the Picea crassifolia forest soil bulk density (0.42 g/cm3) ; the soil bulk density of Picea crassifolia forest gradually closed to the sloping pasture with increase of soil depth.Compared the water retention of Picea crassifolia forest with the sloping pasture's (comparison), the average maximum water holding capacity of soil layers were 131.9% and 27.15%, the average minimum were 79.95% and 15.05%, and the capillary water and 20.22% 105.1%; In the soil surface, soil water holding capacity, the minimum water holding capacity and capillary water holding capacity of the Picea crassifolia forest were significantly higher than the sloping pasture; The soil water holding capacity, minimum water holding capacity and capillary soil water closed to the sloping pasture with the increased of the soil depth. Soil infiltration rate: Initial soil infiltration rate and steady infiltration rate were higher than the lower soil's infiltration rate,and higher than the sloping pasture soil too.Compared the changes of soil moisture of Picea crassifolia forest with the sloping pasture's(comparison): in the soil surface, soil moisture changed dramatically, and sloping pasture soil water moisture was higher than the Picea crassifolia forest. The soil water content gradually stabilized with the increase of soil depth; seasonal variation of soil moisture content were soil water consumption period (May to June), soil moisture accumulation period (July to August), soil water depletion period (after September), soil moisture stable period (after October).6. When the precipitation passed the canopy of the Picea crassifolia forest in Qilian Mountains, the concentration of mineral elements contained in rain changed and the total into doubled. Most of chemical elements in water content increased, and the largest increased was K, the concentration of precipitation through the rain was 3.4 times than it in the atmosphere; the chemical elements'order was: K>P>Ca> Mg>Zn >Mn >Fe>N >Cu.