Doñana harbours the largest ibero-atlantic wetland forest under Mediterranean climate. Owing to its tight dependence of hydrologic regime, monitoring riparian plant communities is key, not only to track biological responses to local and global environmental changes but also to identify early warning signals of prospective changes in the ecosystem functioning which might affect other species and habitats. In 2002 we started a landscape scale monitoring protocol of riparian vegetation at Arroyo de la Rocina, Soto Chico and Soto Grande, using Landsat TM remote sensing of vegetation. In 2004, the project added a permanent plot network where community (species composition, structure) and environmental data are being recorded in the field every five years. In parallel, we are studying the spatial patterns of functional and phylogenetic herbaceous diversity across environmental gradients and the dendroecology of the main tree species.
Preliminary results of the Normalized Vegetation Difference Index (NDVI) through time revealed shifts in the riparian cover and suggest species-specific temporal signatures for the dominant trees. At the local scale (permanent plots), our data indicate increasing senescence of wetland population structure in la Rocina, associated to the particular persistence strategy maintained by the dominant trees (Salix). Our results so far give rise to new questions about the importance of the hydrologic dynamics, the regeneration patterns and the demogenetic structure of these forest populations if we are to understand their driving processes and to preserve their viability on the long term. Therefore, it is of utmost importance to keep up the riparian vegetation monitoring protocol in the long term, maintaining the remote sensing approach combined with the field sampling.
The general objectives of the research are characterizing the spatial and temporal variation trends in the community structure and in the ecophysiological processes occurring in Southern European wetland forests and to identify indicators of the whole ecosystem vulnerability.
Specifically the present proposal aims at:
-Performing a field validation of the preliminary temporal signatures of NDVI variation identified with Landsat TM images for the main tree species.
-Developing and testing a sampling design for the intermediate scale remote sensing of vegetation across the Doñana wetland forests, using the unmanned aerial vehicle (UAV) recently acquired by LAST-EBD.
-Carrying out the quinquennial sampling protocol of community composition and structure in the established network of permanent plots, to integrate the 2014 data with the 2004 and 2010 samplings and afterwards, combine the field with the remote sensing results.
-Exploring and tracking plant community responses and functional relationships of trees to environmental change.
-Reinforcing and enlarging the collaboration with local researchers in the long-term monitoring program development (Natural Processes Monitoring Team, LAST, LEM).