Study On The Water Ecology Of Oasis Protection Forest

Water resource is an essential and organic part of oasis in arid and semi-arid area. Oasis system shows high water-dependency, surface water and underground water are the lifeblood to maintain its existence and development. Water resource often interacts with other environmental factors, decide the environmental dynamics and quality indicators of environmental state and compose the life material base.Therefore, the paper research systematically the soil water dynamic characteristics in forest land and trees?evapotranspiration-dissipation characteristics in desert-oasis protection forest system, and put forward some suggestions to protection forest sustainable development from the starting point of ecological water-using , the results are as follows: 1. Windbreak and sandbreak forest. In every month (3-lOin) ,in view of soil layer (0-100cm) ,water storage varies in the range of 73.87-123.72mm in Elaeagnus angust~folia forestland ,and it is respectively 73.42-129.35inm,77.63-118.lmm and 83.30-154.91mm in Haloxylon ammondandron forestland ,Hedysarum scoparium盇rtemisia arenaria forestland and control land,which shows that under the condition without irrigation supply, the sand natural water content decrease due to the trees?evapotranspiration-dissipation function. In forestland ,the vertical distribution of soil water content is slightly complicated ,thanks to the mbined impact of rainfall amount rate decreases with increased soil-layer-depth and appears minimum in the layer of 80-100cm, in Haloxylon ammondandron forestland and Hedysarum scoparium+Artemisia arenaria forestland. In Elaeagnus angust~foIia forestland, it firstly decreases with increased soil layer-depth, then increases with increased depth, in the layer of 50- 65cm soil water content is minimum. In each soil layer ,the maximum peak value of soil water content rate appears gradually with increased rainfall times. It appears earlier in control land than in tree land ,forestland with small canopy density, thin litter layer and no soil-covering is earlier then in the above forestland. Moreover soil watering is earlier content rate 3 changes more gently from soil surface layer to under layer. When rainfall amount is under 200mm,because of soil-covering affecting water permeation, it affects seriously the normal growth of Hedysarum scoparium which is a deep-rooted tree species, and make the Hedysarum scoparium+Artemisia arenaria forestland develop gradully as the community whose constructive species is Artemisia arenaria. 2. Populus protection forestland. In growing season ,the average soil water 0 content rate in 0-10cm soil layer are 4.13%,3.72% and 4.90%respectively in Populus. a/ba Var pyramisdalis forestland ,P gansuensis and P tonic nttosa forestland and it amount to 149.95mm,13l.47mm and 173.17mm respectively water storage .If other conditions are generally identical in Populus gansuensis forestland,soil moisture is the state of relative low-content and low storage. According to water absorption and utilization state of tree root in Populus protection forest and soil moisture changing state, soil moisture state in forestland can be divided into three action levels: less-soil moisture-utilized layer (0-1 Ocm),soil moisture-utilized layer (20-60cm) and soil moisture-regulated layer(60-1 00cm). 3 the seasonal cha...