Research On Litter Water-holding Characteristics And Soil Hydrological Effects For Four Kind Of Artificial Forests Of Lanzhou Southern Mountain

As very important layers of the forest ecosystem, forest litter layer and forest soil layer provided many important and unique ecological functions, such as runoff regulation, soil and water conservation and water conservation. Southern mountains of Lanzhou were distributed around the Lanzhou city. due to historical and natural factors and any other factor had great influence on the ecological environment of Lanzhou Southern mountains, the result showed that the soil and water loss was increasing seriously, and the ecological environment became exactly fragile, the main trees of the regions was mainly artificial forest, plant species was unitary, and the soil organic matter content was very low. Therefore, its litter and soil layers were especially important to prevent soil erosion and conserve water. In this paper, four kind of artificial forest of the soil and water conservation science and technology demonstration garden of Lanzhou southern mountain as the research object, the research area set Platycladus orientalis pure forest?Fraxinus chinensis pure forest?Populus canadensis Moench pure forest?Robinia pseucdoacacia pure forest to studied the hydrological characteristics of litter layer and soil layer through the field observation and laboratory test to collect data, So as to provide reference for the enhance and improve the ecological function of forest vegetation of Southern mountain of lanzhou or even other regions, especially in soil and water conservation and water conservation function improvement.The main conclusions are as following:(1) The litter storage capacity of four kind of artificial forests had obvious differences, the total tendency was ranged from 9.99 ~30.62 t·hm-2, the order of the litter storage capacity was Platycladus orientalis pure forest(30.62t/hm2)? Populus canadensis Moench pure forest(14.66t/hm2)?Fraxinus chinensis pure forest(12.35 t/hm2)?Robinia pseucdoacacia pure forest(9.99 t/hm2), litter storage content of half-decomposed was much higher than un-decomposed except Robinia pseucdoacacia pure forest; Litter layer thickness of four kind of artificial forests varied from 3.9~4.4 cm, the order of its from high to low was: Populus canadensis Moench pure forest(4.4 ?)> Fraxinus chinensis pure forest(4.3 ?)?Robinia pseucdoacacia pure forest(4 ?)> Platycladus orientalis pure forest(4 ?).(2) the maximum water-holding capacity and maximum water-holding rate of the four kind of artificial forest had obvious differences. As a whole,the water-holding capacity of broad-leaved tree species was the much stronger than coniferous species. The order of maximum interception amount was Platycladus orientalis pure forest(66.36t/hm2)> Populus canadensis Moench pure forest(32.69t/hm2)>Robinia pseucdoacacia pure forest(23.87t/hm2)>Fraxinus chinensis pure forest(19.49 t/hm2);the average maximum interception rate ranged from173.45~245.74%; the average of modified interception rate of un-decomposed was different from half-decomposed; Modified interception amount of four kind of artificial forests ranged from16.35~54.54t·hm-2, equivalently to 1.64~5.45 mm of rainfall interception. According to the variation tendency of the maximum interception amount and modified interception amount, the retaining capacity of the Platycladus orientalis pure forest was the strongest among four kind of artificial forests.(3)The water-holding progress and water absorption rate of litter different layers had same variation tendency for four kind of artificial forest, according to the study results, we can find that: the speed of water-holding amount and water absorption rate was the most quickly at the beginning, gradually became slowed with the time went by, in the end, water-holding content and water absorption rate up to saturation state and no longer change when it was 24 hours, by regression analysis, the water-holding capacity and soaking time of litter can be calculated with the formula W = a l n(t) +b, and water absorption rate and soaking time of litter can be fitted with formula V = k t n, in which t is the soaking time.(4) Among the vertical sequence, the soil bulk density of four kind of artificial forest was constantly increasing with the increment of soil depth, however, in different soil layers, the soil total porosity and soil water-holding amount are gradually decreased with the increasing depth. the soil bulk density ranged from 0.73 g/cm3~0.9 g/cm3, The total porosity of Robinia pseucdoacacia pure forest was the largest(40.26%), Populus canadensis Moench pure forest was the least; the change rule of soil water-holding amount from large to small was Robinia pseucdoacacia pure forest>Platycladus orientalis pure forest> Fraxinus chinensis pure forest>Populus canadensis Moench pure forest. We could find that the variation tendency of the indexes along with the change of soil layer depth were all fitted by the regression equation, according to the result of regression analysis between soil bulk density and soil depth, soil porosity and soil depth,soil water-holding capacity and soil depth, regression coefficient R2 was 1.000, explained fitting result was very ideal.