Study On Water Use Strategy Of Populus Euphratica Under The Different Moisture Gradient

Selected natural growth Populus euphratica in Ebinur wetland nature reserve as theexperimental materials, according to the moisture gradient in vertical direction to choosethe crown, diameter at breast height and growing close, we choose three Populuseuphratica sample plots, using Probe12, soil water potential, leaf water potential, andenvironmental data analysis of fluid flow and the water environmental factors on theresponse, as well as comprehensive Li-6400portable photosynthesis meter,meteorological data to explain Populus euphratica water use strategy. Study at the threedifferent moisture gradient in Ebinur area of Populus euphratica water features,transpiration and water consumption, are discussed under different soil moistureconditions of these indicators in time and space change rule, designed to revealdrought-resistant physiology of Populus euphratica in different moisture gradient, themechanism and the differences of water use strategy, and provide the reference value fornatural vegetation restoration in Ebinur areas.The main conclusions are as follows:（1） because the sample in different geological conditions, especially the difference ofsoil moisture content is obvious. Liquid flow rate, change the shape of the curve isroughly same, peak and minimum appeared back into the phenomenon. Populuseuphratica root saps flow rate and the change of environmental factors on the time is notsynchronized, there is a significant delay. The different sample’s root sap flow of Populuseuphratica in night there are significant differences, in sample plot1the sap flow ofPopulus euphratica at night is0.746kg strain^-1, accounted for16.7%of total throughoutthe transpiration; sample plot2the sap flow of Populus euphratica is0.422kg strain^-1inthe night,17.3%of the total transpiration throughout the day; sample plot3the sap flowof Populus euphratica is0.478kg strain^-1in the night, accounting for19%of the total transpiration throughout the day. Populus euphratica in different moisture content thecondition of water consumption is shown as: sample plot1（water hydrated）> sample plot2（water normal）> sample plot3（water lack）. In addition, high water consumption ofpopulus euphratica, explain its water retention is small, so all the capacity size of for:sample plot3> sample plot2> sample plot1.（2） Synthesis the change law of soil water potential of Populus euphratica, sample plot1in a deep enough moisture, moisture content is very high, plant back to high waterpotential ability is strong. Sample plot2soil water potential showed irregular changetrend of the "W" type. In sample area3, soil water potential changes are different, surfacesoil is dry, water condition is bad.（3） kinds of leaf water potential value in general is great in the morning and night, atnoon and afternoon is small, the maximum occurs generally in the morning. Sample plot2and sample plot3of Populus euphratica in drought stress condition, and the sampleplot3level of drought stress is deeper, the water consumption is low, high waterretention.（4）The water physiological characteristics of Populus euphratica in different sampleappear the difference. The transpiration rate of Populus euphratica in Sample plot1and3is “unimodal” curve, sample plot2distribution characteristics of daily variation oftranspiration rate for" double peak "curve. Recently the river’s Populus euphratica Tr isstronger than the dry sample. Overall, for Populus euphratica water use efficiency,sample plot3> sample plot2> sample plot1. For the stomatal conductance, sample plot1> sample plot2> sample plot3.（5）According to the correlation analysis showed that, in the different moisture gradient,influence factor of photosynthetic rate and transpiration rate of Populus euphratica indifferent sample is different. Effect sample plot1and sample plot2net photosynthetic rate and transpiration rate of the main environmental factors is light intensity, thestomatal conductance of the effect is also very obvious, the influence of transpiration ratefactor still have water use efficiency, impact sample area3net photosynthetic rate,transpiration rate of environmental factors is light intensity, air temperature and airrelative humidity, physiological factor is stomatal conductance and water use efficiency.（6）Using stepwise regression analysis to determine the influence in the growing seasonwater use efficiency （WUE） of Populus euphratica. The water use efficiency in Sampleplot1is mainly affected by the Positive influence on transpiration rate, intercellular CO₂concentration, the concentration of CO₂in the atmosphere, the negative effects of airtemperature; Sample plot2WUE affected by atmospheric CO₂concentration,intercellular CO₂concentration, and vapor pressure deficit （VPD） positive influence;Sample area3water use efficiency is mainly affected by the positive influence onintercellular CO₂concentration, air temperature and air relative humidity, affected by thenegative influence on photosynthetic effective radiation.（7）The Populus euphratica of sample plot3in the furthest distance from the river, andby their low water consumption, high capacity and high water use efficiency ofcharacteristics to resist drought, belongs to the conservative on water use strategy.Sample area1Populus euphratica closest from the river, itself is of high waterconsumption, low leaf water retention and low water use efficiency （WUE）, belongs tosplurge on water use strategy. Sample plot2in the middle of the sample plot1andsample plot3, away from the river far away, also tend to conservative water use strategy.