Foredune vegetation patterns and alongshore environmental gradients: Mozambique Beach, Santa atarina Island, Brazil

摘要

This paper examines patterns of foredune vegetation along an embayment in southern Brazil and the relationships between variations in percent cover and diversity, and environmental factors such as beach/surfzone type and exposure to wind and wave energy. The study was conducted on Mozambique Beach, Brazil, which displays significant alongshore variations in exposure to the prevailing winds and waves, beach/surfzone morphodynam.c type, tvne and dimensions of the dune systems and foredune vegetation cover and diversity. Two vegetation surveys were carried out in contiguous 1 m2 quadrats across the foredune. The nresence/absence, percent cover of the species, diversity and similarity between the vegetation of the profiles surveyed and their relation with environmental conditions are examined. The results show that the vegetation cover decreases from south to north, possibly reflecting the increasing exposure to wind and wave energy. Distinct patterns of species distributions occur along Mozambique beach, such that different plant species are dominant on the southern middle and northern ends of the beach. A cluster analysis demonstrated two associations- the first one is represented by the profiles located in the lower energy zone of the beach, and the second association is represented by the profiles more exposed to wind and wave energy, sediment deposition and salt spray. The diversity of species decreases northwards, possibly influenced by the surfzone type, number of breaking waves and degree of aeohan transport The presence/absence of the species and the vegetation cover on the foredune reflect the varying levels of exposure of the beach and foredune to the winds and waves and also reflect the volume of sediment deposition on the foredune and the beach mobility determined by the morphodynamic beach/surfzone type.