Seasonal and microclimatic influences on the ecophysiology of Mediterranean coastal dune plants

The coastal dune environment, due to the complex coast-to-inland gradient, contributes greatly to plant bio- diversity. The ability of plants to withstand the harsh conditions of this habitat leads to a peculiar vegetation profile which may be affected by the natural and artificial degradation of the coast. Given that these disturbances are likely to increase in the future, there is a great interest in increasing the knowledge of resistance mechanisms allowing plants to colonize this stressful environment. Our focus was on physiological stress markers that could be early signals of changes before ecological disturbances become evident. Three representative species of the different dune zones, Achillea maritima, Ammophila arenaria and Helichrysum stoechas were studied during the four seasons. Winter and summer were confirmed as the most critical seasons with different levels of stress depending on the coast profile where plants grew. The shoreline-inland gradient of stress conditions was evident only for A. arenaria, whose physiology was negatively affected in foredune during summer and for this reason this species could be a useful indicator of increasingly harsh environmental conditions. Physiological perfor- mances of the studied species changed across the seasons and the occupied niches, in accordance with the respective strategies of resistance.