Distribución espacio-temporal de la vegetación en estuarios marealesinteracciones entre las especies nativas e invasoras

Résumé

The analysis of the spatial and temporal distribution of the vegetation in estuaries is necessary for these ecosystems’ management. For this, mapping tools are required, for example, to detect invasive species such as Baccharis halimifolia. This North American species is a major threat for European estuaries, due to the changes that it produces in the environmental conditions at local scale and the displacement of native species like Juncus maritimus. This thesis analyses the spatial and temporal dynamic of these two species at a local scale, by developing procedures to map them in the estuary and studying their interaction through laboratory experiments. All procedures were developed in the Oyambre estuary, located in the norther coast of Spain. The main results are a procedure to map B. halimifolia using imagery from the Landsat and Sentinel satellites; the experimental characterization of the survival capacity and seedling length in relation to the salinity, immersion time and interspecific competition; and the development of a species distribution model that consider physiological information (generated in the experimental stage of the thesis). The developed procedures allowed to map the species, and to carry a retrospective and a prospective analysis of the species’ dynamic in Oyambre. The general conclusion is that B. halimifolia is less tolerant to changes in the environmental conditions in its early development stage, but becomes highly tolerant to those environmental conditions once its individuals are established. This facilitates the displacement of J. maritimus, being this species more tolerant in its early stage, but then becoming more affected by the environmental conditions throughout its growing stage. Nevertheless, after a major perturbation such as the tidal restoration in the estuary, the Baccharis halimifolia population is eliminated and it is unable to recover its initial distribution, due to the high salinity and immersion time. Juncus maritimus also sees its distribution affected, but it is able to recover it after a three-year period (approximately), in which the native vegetation communities are restored.