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Universitat Autònoma de Barcelona (2015)

Forest acclimation to increasing drought : structural and functional changes

Barbeta I Margarit, Adrià

Titre : Forest acclimation to increasing drought : structural and functional changes

Auteur : Barbeta I Margarit, Adrià

Université de soutenance : Universitat Autònoma de Barcelona.

Grade : Doctoral Thesis 2015

Résumé
The anthropogenic climate change is producing a reduction of the precipitation and a change in its regime in regions such as the Mediterranean Basin, which will be intensified during the next decades. Warmer temperatures are amplifying the effects of droughts by enhancing soil evaporation and increasing the atmospheric evaporative demand. In recent years, there has been an increase in reports of forest declines related to drought. They involved widespread crown defoliation and mortality and were usually related to a single extreme drought episode. However, other large-scale changes in forest structure and composition have been linked to the progressive reduction of water availability. Co-occurring woody species may show contrasting drought sensitivity, so increasing drought may produce shifts in species composition and deep modifications of ecosystems’ structure and function. Therefore, understanding species-specific water-use strategies may help elucidate which physiological and/or morphological traits play a key role in determining the effects of droughts on forests. In this sense, drought experiments are a useful tool, but they are usually of short duration while woody species are long-lived organisms. Changes in plant communities occurred on the short-term may not be representative of the future performance of individuals and communities. For this reason, long-term experiments can provide better insights on the dynamics of forests. In this thesis, I examined the effect of long-term (13 years) experimental and natural droughts on holm oak (Quercus ilex) forests. I studied how drought affects the movement of water from belowground to the atmosphere at the individual level in co-occurring species with different drought sensitivity. At the stand-level, I evaluated whether the effect of experimental drought on growth and mortality rates changes over time and after extreme drought events. I also performed a quantitative synthesis on the use of groundwater by plants as estimated with stable water isotopes

Mots clés : Sequera ; Drought ; Sequía ; Alzinar ; Holm oak ; Encinar ; Boscos ; Forests ; Bosques

Présentation et version intégrale (TDX)

Page publiée le 29 novembre 2016, mise à jour le 13 février 2019