Impacts of elevated CO2 concentration on water use efficiency in cropland ecosystems:A meta-analysis of climate chamber controlled experiments
21 articles related to climate chamber controlled experiments from 1985 to 2020 were selected to study the effects of elevat-ed CO2 concentration on water use efficiency(WUE)of the farmland ecosystem by the meta-analysis method.The results showed that under the control of the climate chamber,the increase of CO2concentration had a positive impact on water use efficiency(WUE)with an increase ratio of 20%.Furthermore,it had positive and negative effects on carbon accumulation and evapotranspiration with the ef-fects of 34%and-4%,respectively.However,all the responses had significant heterogeneity(P<0.05).The results also found that the effect of elevated CO2 concentration on WUE was significantly positively correlated with the effect on carbon accumulation(P<0.05),but not significantly correlated with the effect on evapotranspiration(P>0.05).The heterogeneity analysis results indicated that the effect of elevated CO2 concentration on WUE was significantly different among various crops,and the effect on soybean and tomato was significantly higher than that on wheat(P<0.05).Moreover,the effect of elevated CO2 concentration on WUE was significantly cor-related with light intensity,temperature and soil relative water content(P<0.05),among which,there was a negative correlation with light intensity,a positive correlation with temperature and soil water content,but no significant correlation with CO2 enrichment.
elevated CO2 concentrationcropland ecosystemswater use efficiencymeta-analysisclimate chamberenvironmental factors
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