Limited capacity to cope with excessive light in the open and with seasonal drought in the shade in Mediterranean Ilex aquifolium populations |
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Authors: | Ismael Aranda Thomas Matthew Robson Jesus Rodríguez-Calcerrada Fernando Valladares |
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Institution: | 1. Instituto Nacional de Investigaciones Agrarias y Tecnologías Agroalimentarias, Centro de Investigación Forestal, Unidad Mixta INIA-UPM, Carretera Coru?a Km 7.5, 28040, Madrid, Spain 2. Unidad de Anatomía, Fisiología y Genética Forestal, Escuela Técnica Superior de Ingenieros de Montes, Universidad Politécnica de Madrid, Unidad Mixta INIA-UPM Ciudad Universitaria s/n, 28040, Madrid, Spain 3. Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, CSIC, Serrano 115, 28006, Madrid, Spain 4. Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnológicas, Universidad Rey Juan Carlos, c/Tulipán s/n, 28933, Mostoles, Spain
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Abstract: | Climate change is expected to involve more-frequent and intense summer droughts in the Mediterranean region. This represents
a threat for long-term persistence of woody species, such as European holly (Ilex aquifolium), that originated under humid climates during the Tertiary period. The capacity of this species to persist under increased
water stress, both in gaps and in the understory of an oak-dominated woodland, was assessed by quantifying phenotypic plasticity
in response to drought and shade. Physiological responses in plant-water relations and gas exchange were used as performance
indicators under the different environments. Phenotypic plasticity of drought-stressed holly trees in response to changes
in the light environment was low relative to the known response of co-occurring forest trees. Differences between morphological
traits (e.g. specific leaf area and leaf: sapwood ratio in twigs) of sun- and shade-grown trees were small but significant
while physiological traits were largely unresponsive to light availability. This supports the hypothesis that late-successional
shade-tolerant species exhibit greater morphological than physiological plasticity. Sapling acclimation capacity through physiological
mechanisms such as osmotic adjustment was insufficient to protect from summer drought. Holly mainly inhabits oceanic climates
where extreme temperatures and droughts are unusual. Our results suggest that the species occupies a narrowing niche in continental
Mediterranean habitats, and may lack the capacity to persist under more-severe future climate scenarios because of its low
phenotypic plasticity in response to light and drought stresses. |
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Keywords: | Water stress Plasticity Acclimation Holly Climate change |
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