Ecological Use Of Water Of Forest Lands In Guangming Small Watershed In The Upper Reaches Of Ashihe River

In this paper, the ecological use of water of 5 forest lands in the upper reaches of Ashihe river was studied.Larix gmelinii, which was significantly different (P<0.05)from the others, had the lower bulk density as well as the higher porosity and water storage ability among the 3 artificial forests. The stable infiltration coefficient at 10℃of Larix gmelinii (4.86mm/min) was the biggest,followed by mixed forest(1.71mm/min),Fraxinus mandshurica (0.78mm/min),Pinus koraiensis(0.63mm/min) and Pinus sylvestris var.mongolica (0.57mm/min). The conclusion was that the water conservation function of Larix gmelinii was the best among the 5 forests.The vertical change of soil moisture content distribution was obviously decreased with the depth except Fraxinus mandshurica. In the layer of 0-40cm, the soil moisture content of Larix gmelinii,Fraxinus mandshurica,mixed forest,Pinus koraiensis and Pinus sylvestris var. mongolica was 32.91%,28.79%,25.99%,23.64% and 18.76% respectively. The soil moisture in the growth season followed the high-low-high-low law, and changed along with precipitation. Forests played an important role in the dynamics of soil moisture content in the small watershed.The daily dynamic of transpiration intencity presented one peak, and the maximum reached at 12:00-14:00. The transpiration intencity of broad-leaf forests was bigger than the coniferous forests. The transpiration values were as follows, Fraxinus mandshurica (247.09mm)> mixed forest (170.18mm)>Larix gmelinii (167.17mm)>Pinus sylvestris var.mongolica (152.29mm)>Pinus koraiensis (117.76mm).The transpiration values were all smaller than the precipitation. It didn't present the phenomenon of lack of water in the small forest watershed.The diurnal variation of soil evaporation showed a single peak curve pattern,and the peak value accured at 10:00-14:00. The evaporation intensity during growing season was in such sequence:late July(0.62mm/d)>middle August(0.50mm/d)>late August(0.47mm/d)>middle September(0.45mm/d)>late September(0.26 mm/d). The evaporation intensity and soil water content showed the negative correlation.The ecological use of water of 5 forest lands was that Larix gmelinii(604.33mm)>Fraxinus mandshurica(599.09mm)>Pinus koraiensis(546.07mm)>mixed forest(500.20mm)>sylvestris var.mongolica(472.36mm). The evapotranspiration was 27%-41% of the ecological water use. The soil water storage was the main part of ecological water use in this small watershed.The conclusion is that the stand structure, such as the composition of tree species,age and spatial structure, should be changed in the small forest watershed. Use water resources reasonably, ensure the ecological use of water of forest ecosystem, coordinate the relation between environmental improvement and economic development, enhance three effects of forest ecosystem.