Study On Water Consumption Characteristics Of Three Typical Afforestational Trees In Mu Us Sandy

Water resource in Mu us Sandy land is much short-handed, meanwhile more and more trees are being planted which needed to be irrigated, on this background we took a research on the evaportranspiration of three typical trees:Hedysarum scoparium, the mean indigenous tree,Populus bolleana Lauche, Pinussylovestrisver.Mongolica, trees of shelter belts and towns. From April to October in2011, we study the transpiration of this three trees, the water equilibrium of soil-plant syatem, base on which we calculate the appropriate density or space between trees. Finally, we got results as follows:1、In the whole growing season, April to October, the four Hedysarum scoparium with stems of30mm,20mm,15mm,9mm have consumed water of1045.4L、379.7L、311.1L、59.7L respectatively, Water consumption increasing from May to July, reach the maximum in August。2、Populus bolleana Lauche with stems of (91mm,96mm)consumed water of5383.5L,5607.8L respectively, Pinussylovestrisver. Mongolica, stem of30mm used up water of2479.3L。The accumulation of water consumption in the whole growing season is in direct proportion to leave area and stem diameter。2、Diunal variation of sap flow fluctuation is transitionally changing in the growing season, adjusting to its way of water consumption.3、In rainy and cloudy days, sap flow of the three trees are influenced obviously, in the nights of rainy days, sap flow of Hedysarum scoparium reach the maximum, in the day time it is only1/4of that in fine days, in the fellowed days, it recover rapidly and increase in some extent. Sap flow of Pinussylovestrisver. Mongolica, in rainy days is rather slow in both daytime and nighttime, and recover the previous pattern. In rainy days, sap flow of Populus bolleana Lauche stay smooth and steady, without fluctuation. When soil moisture reach the maximum in rainy days, they absob water in different ways, which reflect that the dynamic of water absoption diverse in the three trees. Transpirational pull and root pressure, two ways of active/initiative water absorption, and passive absorption of water. 4、The vertical distribution of soil moisture content was observed throughout the whole growing season, water replenishment and consumption is different in every layer. Over the50cm, water content rise and fall rapidly, it is the rapid change layer, on the surface water is easiest to change for rain, dew and evaporation. In the20-50cm layer, water supplied by infiltration and used by root absorption. In60-100cm layer, soil moisture content is relatively stable, only precipitations over40mm is able to obviously infiltrate into80-100cm layer. Form the beginning to the end of growing season, the water wane in Hedysarum scoparium woosland is20.7mm, water wane in Pinussylovestrisver. Mongolica woodland is21.8mm.5、In light of the water consumption of tree transpiration that of soil evaporation of forest plot and the precipitation quantity under an assurance rate as80%during the growth season, the least water nourishment area for a Pinussylovestrisver. Mongolica with stem of3cm is12.8m2,,and the current density of planted forest is over, the appropriate density is3*4, two time of the atual density.For Populus bolleana Lauche with stem of8to10cm the least water nourishment area is28m2, Hedysarum scoparium with stem of3cm need a least water nourishment area of5.3m2.