Earlier summer drought affects leaf functioning of the Mediterranean species Cistus monspeliensis L.

The Mediterranean vegetation is characterized by a high diversity of growth forms, habits and phenology that enable it to endure under harsh environmental conditions. It is however unclear whether these adaptations may allow plant survival under more extreme conditions, as predicted by climatic models under the perspective of climate change. A manipulative experiment aiming at anticipating summer aridity has been run to analyse the effects of the experimental drought on spring-leaf functioning and characteristics of the leaf-dimorphic Mediterranean shrub Cistus monspeliensis L. Assimilation rates were reduced under anticipated summer aridity due to a decrease of stomatal conductance, but only before morphological adaptations to drought (an increase of leaf mass per area) occurred. These adaptations were anticipated under experimental dry conditions, and causes photosynthetic performances to recover compared to previous dates. When natural summer aridity occurred, the leaf mass per area also changed in the control. However, this causes no recovery of the photosynthetic performances, because of the decrease of stomatal conductance due to low soil water content and leaf water potential values. Moreover, under experimental drought, leaf shedding was anticipated to reduce water losses, causing an overall reduction of leaf lifespan. (C) 2013 Elsevier B.V. All rights reserved.