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Plant function and evolutionary biology
RESEARCH ARTICLE

Drought-induced mortality selectively affects Scots pine trees that show limited intrinsic water-use efficiency responsiveness to raising atmospheric CO2

Ana-Maria Hereş A B D , Jordi Voltas C , Bernat Claramunt López A B and Jordi Martínez-Vilalta A B
+ Author Affiliations
- Author Affiliations

A CREAF, Cerdanyola del Vallès, Bellaterra, Barcelona, 08193, Spain.

B Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Bellaterra, Barcelona, 08193, Spain.

C Departament of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida, Av. Rovira Roure 191, Lleida, 25198, Spain.

D Corresponding author. Email: ana_heres@yahoo.com

Functional Plant Biology 41(3) 244-256 https://doi.org/10.1071/FP13067
Submitted: 22 March 2013  Accepted: 23 September 2013   Published: 11 November 2013

Abstract

Widespread drought-induced tree mortality has been documented around the world, and could increase in frequency and intensity under warmer and drier conditions. Ecophysiological differences between dying and surviving trees might underlie predispositions to mortality, but are poorly documented. Here we report a study of Scots pines (Pinus sylvestris L.) from two sites located in north-eastern Iberian Peninsula where drought-associated mortality episodes were registered during the last few decades. Time trends of discrimination against 13C (Δ13C) and intrinsic water-use efficiency (WUEi) in tree rings at an annual resolution and for a 34 year period were used to compare co-occurring now-dead and surviving pines. Results indicate that both surviving and now-dead pines significantly increased their WUEi over time, although this increase was significantly lower for now-dead individuals. These differential WUEi trends corresponded to different scenarios describing how plant gas exchange responds to increasing atmospheric CO2 (Ca): the estimated intercellular CO2 concentration was nearly constant in surviving pines but tended to increase proportionally to Ca in now-dead trees. Concurrently, the WUEi increase was not paralleled by a growth enhancement, regardless of tree state, suggesting that in water-limited areas like the Mediterranean, it cannot overcome the impact of an increasingly warmer and drier climate on tree growth.

Additional keywords: die-off, tree rings, water stress, Western Mediterranean, δ13C.


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