Unanticipated effects of stand dynamism on Amazonian tree diversity

Abstract

We assessed a general hypothesis of tropical tree diversity that predicts that species richness will be positively correlated with stand dynamism. Our analysis was based one of the largest and longest-running datasets on Amazonian trees (≥10 cm diameter at breast height), with data collected over a 23-yr period within 66 1 ha plots spanning a large (1000 km2) landscape. Within these plots, maximum tree-species richness (329 species/ha) and Fisher's α values (227.5) were among the highest ever recorded. Contrary to the diversity-dynamism concept, tree species richness in our landscape was significantly and negatively associated with stand dynamism (measured as the mean rate of annual tree turnover). Because of this unexpected finding, we critically re-evaluated the relationship between stand dynamism and tree diversity across the Amazon basin and the tropics as a whole. With the inclusion of additional data we found that the relationship between stand dynamism and tree diversity becomes non-significant at larger spatial scales.