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Xylem and leaf functional adjustments to drought in Pinus sylvestris and Quercus pyrenaica at their elevational boundary

Fernández-de-Uña Laura, Rossi Sergio, Aranda Ismael, Fonti Patrick, González-González Borja D., Cañellas Isabel et Gea-Izquierdo Guillermo. (2017). Xylem and leaf functional adjustments to drought in Pinus sylvestris and Quercus pyrenaica at their elevational boundary. Frontiers in Plant Science, 8, (1200), p. 1-12.

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URL officielle: http://dx.doi.org/doi:10.3389/fpls.2017.01200

Résumé

Climatic scenarios for the Mediterranean region forecast increasing frequency and intensity of drought events. Consequently, a reduction in Pinus sylvestris L. distribution range is projected within the region, with this species being outcompeted at lower elevations by more drought-tolerant taxa such as Quercus pyrenaica Willd. The functional response of these species to the projected shifts in water availability will partially determine their performance and, thus, their competitive success under these changing climatic conditions. We studied how the cambial and leaf phenology and xylem anatomy of these two species responded to a 3-year rainfall exclusion experiment set at their elevational boundary in Central Spain. Additionally, P. sylvestris leaf gas exchange, water potential and carbon isotope content response to the treatment were measured. Likewise, we assessed inter-annual variability in the studied functional traits under control and rainfall exclusion conditions. Prolonged exposure to drier conditions did not affect the onset of xylogenesis in either of the studied species, whereas xylem formation ceased 1-3 weeks earlier in P. sylvestris. The rainfall exclusion had, however, no effect on leaf phenology on either species, which suggests that cambial phenology is more sensitive to drought than leaf phenology. P. sylvestris formed fewer, but larger tracheids under dry conditions and reduced the proportion of latewood in the tree ring. On the other hand, Q. pyrenaica did not suffer earlywood hydraulic diameter changes under rainfall exclusion, but experienced a cumulative reduction in latewood width, which could ultimately challenge its hydraulic performance. The phenological and anatomical response of the studied species to drought is consistent with a shift in resource allocation under drought stress from xylem to other sinks. Additionally, the tighter stomatal control and higher intrinsic water use efficiency observed in drought-stressed P. sylvestris may eventually limit carbon uptake in this species. Our results suggest that both species are potentially vulnerable to the forecasted increase in drought stress, although P. sylvestris might experience a higher risk of drought-induced decline at its low elevational limit.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:1664-462X
Volume:8
Numéro:1200
Pages:p. 1-12
Version évaluée par les pairs:Oui
Date:2017
Identifiant unique:10.3389/fpls.2017.01200
Sujets:Sciences naturelles et génie > Sciences naturelles > Biologie et autres sciences connexes
Département, module, service et unité de recherche:Départements et modules > Département des sciences fondamentales
Mots-clés:climate change, drought stress, experimental drought, phenology, sub-Mediterranean forest ecosystems, water deficit, wood anatomy, xylogenesis
Informations complémentaires:This Document is protected by copyright and was first published by Frontiers. All rights reserved. It is reproduced with permission.
Déposé le:24 août 2017 13:43
Dernière modification:24 août 2017 13:43
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