PARENT SESSION
Symposium 2: Climate Change and its Consequences on Coastal Dune Patterns and Processes: What Are the Future Perspectives?
Organized by: ML Martinez and P Moreno-Casasola
Monday, August 4. 9:00 AM to 11:30 AM, SITCC Chatham Ballroom B.

Climate change and community dynamics change on coastal dunes.

Martinez, M. Luisa^*,1, ¹ Departamento de Ecologia Vegetal, Xalapa, Veracruz, Mexico

ABSTRACT- Studies on global climate change predict that sea level rise will lead to reduced sediment supply to the beach-foredune interface and therefore, alterations in substrate mobility in inland dunes. This will probably influence natural dynamics of dune vegetation since they are largely affected by (and in many occasions dependent upon) substrate mobility. In a ten-year survey on primary succession occurring in a mobile dunes area (along the coast of Central Gulf of Mexico) it was observed that sand movement played a key-role in species replacement, especially during the early successional stages. The early colonizer (the shrubby legume Chamaecrista chamaecristoides) was the species most tolerant to burial by sand, and seemed to facilitate colonization by late colonizers (tall grasses such as Trachypogon plumosus and Schizachyrium scoparium). Subsequent field observations and experiments demonstrated the occurrence of facilitation: species were spatially aggregated; environmental conditions (wind speed, sand movement, and temperature on the sand surface) were significantly ameliorated by the shrub, and seedling survival of the two grasses was exclusive to the shade of the shrub. The above is evidence of the importance of sand movement for community dynamics. How will it thrive in a scenario of global climate change and altered substrate ability? Markov chains provide a useful tool to predict potential community dynamics and species replacement in two contrasting scenarios. With reduced sand movement, it is predicted that early colonizers might disappear and become locally extinct, which will be problematic for several reasons: the maintenance of the natural vegetation dynamics will lack its naturally restoring species which is keystone after disturbance events; in addition, it is a conservation issue, since Chamaecrista is endemic to the Mexican mobile dunes. With exacerbated sand movement, early successional stages will be maintained and probably the system will remain unstable, negatively affecting late successional stages.

Key words: Markov chains, Chamaecrista chamaecristoides, coastal dunes, Mexico