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Increased water‐use efficiency does not lead to enhanced tree growth under xeric and mesic conditions
Author(s) -
Lévesque Mathieu,
Siegwolf Rolf,
Saurer Matthias,
Eilmann Britta,
Rigling Andreas
Publication year - 2014
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12772
Subject(s) - deserts and xeric shrublands , transpiration , water use efficiency , temperate climate , productivity , pinus <genus> , environmental science , dendroclimatology , biology , agronomy , botany , photosynthesis , ecology , climate change , macroeconomics , habitat , economics
Summary Higher atmospheric CO 2 concentrations ( c a ) can under certain conditions increase tree growth by enhancing photosynthesis, resulting in an increase of intrinsic water‐use efficiency ( i WUE ) in trees. However, the magnitude of these effects and their interactions with changing climatic conditions are still poorly understood under xeric and mesic conditions. We combined radial growth analysis with intra‐ and interannual δ 13 C and δ 18 O measurements to investigate growth and physiological responses of Larix decidua , Picea abies , Pinus sylvestris , Pinus nigra and Pseudotsuga menziesii in relation to rising c a and changing climate at a xeric site in the dry inner Alps and at a mesic site in the Swiss lowlands. i WUE increased significantly over the last 50 yr by 8–29% and varied depending on species, site water availability, and seasons. Regardless of species and increased i WUE , radial growth has significantly declined under xeric conditions, whereas growth has not increased as expected under mesic conditions. Overall, drought‐induced stomatal closure has reduced transpiration at the cost of reduced carbon uptake and growth. Our results indicate that, even under mesic conditions, the temperature‐induced drought stress has overridden the potential CO 2 ‘fertilization’ on tree growth, hence challenging today's predictions of improved forest productivity of temperate forests.