Spatial variability and temporal trends in water-use efficiency of European forests
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The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the lastcentury are likely to have had a profound effect on the physiology of trees: altering the carbon andwater fluxes passing throughthe stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain.Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine theintrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results werecompared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and land–atmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigatedconiferous and deciduous species and themodel results agreed significantlywith a clear south-to-north gradient, as well as a generalincrease in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongestincrease observed and modelled for temperate forests in Central Europe, a region where summer soil-water availabilitydecreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate changeleading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in theland surface schemes of global climate models, where vegetation–climate feedbacks are currently still poorly constrained byobservational data.
Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Tidskrift||Global Change Biology|
|Status||Published - 2014|
|Peer review utförd||Ja|