Context dependency in the maintence of coexistence between two dominant argentine salt marsh plants

GARCIA, E.A.; ALBERTI, J.

Providence

Congreso; 37th Annual Benthic Ecology Meeting; 2008

Understanding the mechanisms that promote and maintain biodiversity is essential for the preservation of biodiversity that is currently threatened worldwide. Salt marsh ecosystems are naturally low in plant species diversity, thus an understanding of the important factors maintaining coexistence in this system is critical. In many Argentine salt marshes there are two dominant plant species Spartina densiflora and Sarcocornia perennis. In areas of low abiotic and biotic stress, S. perennis is the first to colonize, S. densiflora follows and soon dominates. Although, in areas of high abiotic and/or biotic stress the coexistence of these two species is maintained. Here, we examined how the coexistence of these two species is maintained at one site where biotic stress is high (i.e. mammal herbivore) and another where abiotic stress is high (i.e. salinity). We set up an experiment with five treatments, in plots where the percent cover of each species was roughly 50:50; 1) nutrient addition, no shade, 2) control, no shade, 3) nutrient addition with shade, 4) control with shade, and 5) S. perennis removal. We found where there is a high biotic stressor; S. perennis dominates with nutrient addition and with shade x nutrient addition. Although at the site where only abiotic stress is high, S. densiflora dominates with nutrient addition and with shade x nutrient addition. In both sites S. densiflora did worse when S. perennis was removed. These results illustrate the importance of environmental context dependency in influencing the mechanisms affecting biodiversity.