Spatial variability and temporal trends in water-use efficiency of European forests

Research output: Contribution to journalArticlepeer-review


  • Matthias Saurer
  • Renato Spahni
  • David C. Frank
  • Fortunat Joos
  • Markus Leuenberger
  • Neil J. Loader
  • Danny Mccarroll
  • Mary Gagen
  • Ben Poulter
  • Rolf T W Siegwolf
  • Laia Andreu-Hayles
  • Tatjana Boettger
  • Isabel Dorado Liñán
  • Michael Friedrich
  • Emilia Gutierrez
  • Marika Haupt
  • Emmi Hilasvuori
  • Ingo Heinrich
  • Gerd Helle
  • Håkan Grudd
  • Risto Jalkanen
  • Tom Levanič
  • Hans W. Linderholm
  • Iain Robertson
  • Eloni Sonninen
  • Kerstin Treydte
  • John S. Waterhouse
  • Ewan J. Woodley
  • Peter M. Wynn
  • Giles H F Young

External organisations

  • Paul Scherrer Institut
  • University of Bern
  • Swansea University
  • Laboratoire des Sciences du Climat et de l'Environment
  • Lamont-Doherty Earth Observatory
  • Department for Urban and Environmental Sociology
  • Technical University Munich
  • Hohenheim University
  • Universitat Autonoma de Barcelona
  • Finnish Environment Institute
  • Climate Dynamics and Landscape Evolution, GFZ German Centre for GeoSciences
  • Stockholm University
  • Finnish Forest Research Institute
  • Slovenian Forestry Institute
  • University of Gothenburg, Gothenburg, Sweden.
  • University of Helsinki, Helsinki, Finland
  • Swiss Federal Research Institute WSL
  • Anglia Ruskin University
  • University of Exeter
  • Lancaster University


The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the 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 the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared 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 investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation-climate feedbacks are currently still poorly constrained by observational data.


Original languageEnglish
Pages (from-to)3700-3712
Number of pages13
JournalGlobal Change Biology
Issue number12
Publication statusPublished - 1 Dec 2014


  • Carbon isotope discrimination, Climate change, Dynamic vegetation model, Tree rings