Made the Populus euphratica communities as the research object in the extreme drought environment the CO2 flux characteristics and water use efficiency(WUE) during different phenological phases of P.euphratica were studied using the eddy covariance flux observation system.The results showed that the daily variations in the CO2 flux trends were basically identical in different phenological phases of P.euphratica,but there were obvious seasonal differences.The change amplitude ofchange in CO2 flux rate at the maturity stage was the largest,and was the smallest at the flowering stage,and medium at the foliation stage.Correlation analysis showed that the CO2 flux rate of P.euphratica community was significantly correlated with the sensible heat flux,latent heat flux,momentum flux,soil heat flux,net radiation and relative humidity of the air.Among them,net radiation,and latent and sensible heat fluxes were more highly related with the CO2 fluxs,The scope of change,i.e,-0.82—-0.88、-0.64—-0.66 and-0.63—-0.94,respectively,the main environmental factor affecting the CO2 rate of the community.Thus this study shoued an obvios daily change in water use efficiency of the P.euphratica community.The dynamic performance of WUE of the community time was as follows:water use efficiency varied greatly at the flowering stage,leaf coloration stage,and defoliation stage,and was the highest at the flowering stage,most stable at the foliation and maturity stages.Two of the most critical factors affecting the communities were net radiation and wind speed.%以极端干旱环境中的胡杨群落为研究对象,利用涡度相关通量观测系统,研究了胡杨群落CO2通量与水分利用效率在不同物候期的动态规律.结果表明:胡杨CO2通量在不同物候期日变化趋势基本一致,但存在明显的季节差异,其中果熟期CO2通量变化幅度最大,开花期最小,展叶期介于二者之间.相关分析表明,胡杨群落CO2通量均与显热通量、潜热通量、动量通量、土壤热通量、净辐射以及空气相对湿度呈极显著相关.其中,净辐射、潜热通量和显热通量与CO2通量的相关系数较大,其变化范围分别为-0.82—-0.88、-0.64—-0.66和-0.63—-0.94,是影响群落CO2通量的最主要环境因子.胡杨群落水分利用效率(WUE)同样存在明显日变化规律.其时间动态表现为:群落水分利用效率在开花期、叶黄期和落叶期变化幅度大,开花期最高,在展叶期和果熟期WUE最稳定.净辐射和风速是影响群落水分利用效率的两个最关键要素.
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