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Universidad Rey Juan Carlos (2017)

Efecto de las sequías extremas en especies arbóreas mediterráneas y su modulación por el microclima y la fragmentación

Forner Sales, Alicia

Titre : Efecto de las sequías extremas en especies arbóreas mediterráneas y su modulación por el microclima y la fragmentación

Auteur : Forner Sales, Alicia

Université de soutenance : Universidad Rey Juan Carlos

Grade : Tesis Doctoral 2017

Résumé partiel
Extreme drought frequency has increased over the last decades in semiarid areas, such as the Mediterranean region. Moreover, water scarcity in summer which historically affects Mediterranean ecosystems is expected to intensify over the next few years due to ongoing climate change. Water stress produced in those ecosystems has favoured coexisting species that have several water regulation strategies as well as ecophysiological mechanisms which allow species to adapt and recover from an increase in the frequency and intensity of disturbances. However, information about the efficacy of those different adaptations and responses to frequent and recurrent droughts is lacking. Besides, the relevance of many factors able to modulate species response to drought ; amplifying or attenuating its effects, as well as resilience and resistance processes in the short term, are still unknown. The general objectives of this thesis were : (1) understanding the functional response to drought of coexisting Mediterranean forest species and with contrasting strategies, to cope with extremely dry periods ; (2) quantifying the modulation in the response of species to extreme droughts by microclimatic conditions, and (3) assessing the role of forest fragmentation on the ecophysiological response of species to drought. In order to address these objectives, the main ecophysiological variables as well as the timing and intensity of drought were assessed. Moreover, several tracers of the microclimate and habitat fragmentation were considered as possible factors modulating drought responses in Mediterranean forest species. The study was carried out in a Mediterranean forest ecosystem where coexisting tree species have different evolution histories and drought tolerances (Quercus ilex subsp. ballota (Desf) Samp., Quercus faginea Lam. y Pinus nigra J.F. Arnold subsp. salzmannii (Dunal) Franco). Holm oak (Quercus ilex), one of the most representative tree species in the Mediterranean ecosystems, was selected to address the fragmentation effect on drought modulation the selected species was Our results point that the response of Mediterranean forest species to drought events is highly complex, and they differ in their potential ability to cope with extremely dry periods according to species¿ water regulation strategy. Drought-avoiding species such as P. nigra had a certain disadvantage in the carbon balance when events are extreme, which could be accentuated under more frequent extreme events. Microclimate and fragmentation may be significant attenuating factors of extreme droughts and modify the severity of their effects in the study species

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Page publiée le 10 septembre 2017, mise à jour le 1er octobre 2017