Increased atmospheric carbon dioxide makes trees use water more efficiently

University Of Exeter

When the CO 2 concentration in the air increases, the size of the stomatal opening reduces to regulate the amount of carbon acquired which minimises the water lost. As a result the so-called water use efficiency increases. In this study the researchers used measurements of carbon from tree-rings and computer models to quantify tree and forest responses to both climate variation and increased atmospheric CO 2 concentrations. The study showed that reduced stomatal opening increased water use efficiency by 14% in broadleaf species and by 22% in needleleaf species. Despite the CO 2 induced stomatal closure, the models showed that the consequences of a warming climate - lengthened growing seasons, increased leaf area and increased evaporation - resulted in a 5% increase in forest transpiration - the cycle of water through trees.

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