Fidalgo, F.; Santos, A.; Pimenta, S.; Marques, J., and Honrado, J., 2014. Regional environmental gradients influence ecophysiological responses of dominant coastal dune plants to changes in local conditions.

Coastal dunes are dynamic systems exposed to multiple environmental changes; therefore, specific, sensitive, and cost-efficient indicators are needed for ecological assessment and monitoring. We addressed whether biochemical indicators of plant physiological stress could provide a complementary approach to classic disturbance indicators for identifying dune areas undergoing ecological change. We hypothesized that disturbance related to a shift from (meta-) stability to erosive dynamics would promote increased stress on foredune plants, which would exhibit adaptive physiological responses that could be captured through standard biochemical tests. Such responses would anticipate other reported responses of foredune communities, such as loss of facilitation capacity or decrease of species richness. We also hypothesized that such responses would be influenced by biogeographic context, based on reported interactions between regional and local gradients. We compared patterns of proline accumulation and membrane lipid peroxidation in plants of sand-couch (Elytrigia juncea), a foredune specialist, from 27 transects at nine locations under contrasting dynamics along a climatic gradient in northern Portugal. Next, we evaluated effects of coastal dynamics and biogeographic context on proline accumulation and lipid peroxidation and compared physiological stress patterns with variations in topographic and phytocoenotic attributes of dune ecosystems related to contrasting coastal dynamics. We found proline accumulation to be significantly higher (and lipid peroxidation proportionally lower) in plants from sites under chronic erosive dynamics. This response of physiological stress indicators was further confirmed by their significant correlation with topographic and phytocoenotic indicators. We also confirmed significant effects of regional gradients on the ecophysiological responses to contrasting coastal dynamics, which were better discriminated under Mediterranean climate than among Atlantic sites. This interaction between regional climate and local disturbance suggests caution in the wide use of ecophysiological responses for ecological assessment and monitoring before regionally stratified models are calibrated to compensate for interactions among processes operating at different scales.