Mudanças temporais na composição florística e funcional da comunidade de lianas Bignoniaceae na Amazônia Central

Abstract

The structure of liana communities has changed over time in various tropical forests. In Central Amazonia, the patterns of increase in stem density and basal area of lianas are controversial. The taxonomic and functional composition of liana assemblages in these forests is structured along a hydroedaphic gradient. However, we still do not know whether species composition and their traits are changing with time. In this study, we investigated changes in the taxonomic and functional composition, and its relationship with species richness of the Bignoniaceae liana assemblage over a 10-year interval (2004 to 2014), assessing whether these changes are modulated by the hydrological gradient. In addition, we evaluated whether the functional traits of species explain temporal variations in abundance and relative basal area during this period. We sampled liana species composition in 30 plots, and their functional composition in 17 plots of the Ducke Reserve. Furthermore, we assessed resprouting capacity, leaf traits, and wood characteristics of 10 liana species and their influence in the temporal change in stem density and basal area of these species. We evaluated whether there were taxonomic and functional changes over the 10-year period using a paired t-test utilizing the taxonomic and functional compositions of the plots summarized in NMDS axes and Principal Component Analysis (PCA), respectively. We related temporal changes in taxonomic and functional species composition, and species richness with the hydrological gradient through simple linear regressions. Through linear regression analyses, we assessed changes in species abundance and relative basal area with the selected functional traits. We did not identify changes in the taxonomic or functional composition of lianas throughout the analyzed years in this study. The hydrological gradient showed a negative relationship in respect to changes in species richness, whose environments closer to the water table exhibited little or no species loss, while more distant environments tended to show species loss over time. We did not observe an increase in the relative stem density of species, and the functional traits analyzed did not explain this pattern. However, we found that changes in the relative basal area of species had a positive relationship with resprouting capacity, indicating that species with a higher resprouting capacity tend to have a greater basal area over time. Our study shows that, over a ten-year window, the local hydrological gradient can modulate the richness of liana assemblages in Central Amazonia. Also, greater area occupied by species may reflect a trait related to their physical wellness.