Study On The Hydrological Characteristics Of Water Conservation Forest In Qilian Mountains

The study was carried on in the Xishui Area of the Pailugou Catchments, Qilian Mountains.Adopted fixed position observation method, based on catchment dimensions, the forest hydrological effect were studied from rainfall input, canopy moisture transmission, moss and litter moisture transmission, the earth's surface runoff, forest soil layer moisture dynamic state, soil moisture physical properties and soil moisture infiltration regulation's and so on. The results showed that:(1)Experimental basin annual amount of rainfall was 394.2 mm, not only rainfall rarely, but also annual inside allotment very unbalance, rainfall main concentration in 5-9 months, which was 87.62 % of the year rainfall, but winter rainfall only 12.38%. With the elevation hoist increaseing, rainfall quantity also increasing.Average rainfall increased 4.95% when elevation was increased per 100 meters .The elevation 2600-3300 m annual amount of rainfall to present to increaseing trend, but the elevation 2600-2900 m pass to increase more quickly; 2900-3300 m pass to increase slower.When elevation over 3300 m and close summit of hill, the annual rainfall descend with the elevation rising.(2)Rainfall interception allotment regulation of canopy of Picea crassofolia forest, moss and litter layer, soil layer.It showed that the average interception rate were 35.29%, 9.23%, and 53.61%, interception quantity rescpective were 139.1 mm, 27.24㎜ and 178.92 mm.Inside forest rainfall beginning to penetrated rain just when outside forest rainfall level beyond 0.8mm.When outside rainfall level 13.26 mm cans observation tree trunk liquid.(3)Each forest type water-holding quantity is 3058.2-4383.8 t·hm-2 in experimental basin,and forest soil water-holding quantity is higher(3442.32-4383.8 t·hm-2)than non-woodland soil( 3058.2 t·hm-2 of grazing grass) , forest water-holding of all forest type Picea crassifolia forest and scrub forest were higher than that of Sabina prezewalskii forest .(4) Except to the south-facing slope grazing grass caused soil erosion, forest land not occurrence the earth's surface runoff and soil erosion phenomenon. Rainfall put grazing grass to south-facing slope erosion with grazing degree but dissimilarity, excessiveness grazing small area annual runoff and soil runoff quantity largest, difference were 136.3 mm and 3157 t·ha-1, which was 4.2 times and 45.6 times of medium grazing small area, and was 290 times and 1337 times of light degree grazing small area.Embodied by the forest plant conservation and adjust rainfall effect very obviously.(5)Soil moisture with season variety was divided into: soil moisture consuming period, accumulating period, losting period and stabiliz-ing period.Its include easy available water,semi-available water and difficult available water according to the plant physiology use water;The vertical variety of the soil the moisture can be divided into soil moisture easy-changing layer, utilizing layer and adjusting layer.Every variety woodland of annual average water-holding quantity with shrubs tallest was 315.2 mm, Moss crassofolia forest. Sabina przewalskill forest was 256.72 mm and 238.45 mm, grazing grass be minimum to 158.62 mm.The soil moisture of the basis woodland usefulness analysis, Moss Picea crassofolia forest moisture supply condition very best;shrub forest water quantity not only higher,but the surplus moisture be excessive, influence plant growth; Sabina przewalskill forest and grazing grass moisture supply more badly. The raining season was experiment basin the best forestation season.(6)Junior permeability, steady permeability and coefficient permeability of Moss crassofolia forest permeate coefficient all higher than other types, the next was scrub forest, non-stocked and grazing grass because of have no litter, soil body the structure be tight solid, permeability function very worst.(7)The soil moisture evaporation be subjected to humidity level and wind speed etc. factors of influence more bigger, there exists a definite relation between wind speed(x) and intensity of relatively evaporation(y), strength(y).namely y = 3.0507x0.4835, (R2= 0.9702), It was indicated that soil region evaporation process promoted with wind speed increasing and evaporating intensified.Therefore, how to protect woodland preservation of soil moisture, keep forest growing soil moisture seem to be importance in the Qilian Mountains.(8) The biggest water-holding quantity and valid water-holding of scrub forest accumulation respectively were 23.83-134.95 t·hm-2 and 17.25-83.62 t·hm-2, the soil the biggest water-holding quantity and valid water-holding quantity of it respectively were 2439.20-3409.00 t·hm-2 and 518.5-1015.50 t·hm-2. Scrub forest has good water conservation function.