Diversity and dominance patterns in Amazon coast dune forest island tree communities

摘要

Aiming to better understand richness, dominance, diversity and community changes of coastal vegetation, we studied woody plant communities and soil parameters of equatorial dune forest islands. We investigated four sites isolated by mangroves (Buraco Beach, Bonifacio, Camaraua double dagger u, Apeu-Salvador) and compared data to a paleodune forest with higher floristic and structural complexity (Salinas do Roque) for assessment of the regional species pool. We determined grain size distribution and organic matter content at Buraco Beach, Camaraua double dagger u and Apeu-Salvador. Grain size distribution was similar among sites but upper soil layers at Camaraua double dagger u showed low organic matter contents. We recorded trees and shrubs along several transect plots crossing forested dune ridges and surveyed areas outside of plots for additional species. Richness was lower at Camaraua double dagger u (18 species vs. 25, 26 and 28 at Bonifacio, Apeu-Salvador and Buraco Beach, respectively). Fisher's alpha ranged between 3.2 and 4.7, Pielou's J' between 0.70 and 0.80. R,nyi profiles confirmed lower diversity for Camaraua double dagger u, dominated by a small group of species with high importance values. Within-site beta diversity was lowest at Buraco Beach. Species were mainly wide-spread generalists. We found low richness compared to the Salinas do Roque reference site; null model tests indicated that the species pool of the dune sites was partly shaped by environmental filtering. We attribute differences in species composition and diversity/dominance patterns among the four dune sites to distance to the mainland and stochastic events with effects on non-standard long distance dispersal.