Species density diverges after forest fragmentation in lianescent Machaerium Pers. (Fabaceae) in Central Amazonia

Abstract

Liana density is positively associated with forest fragmentation. The process of colonization by lianas is often reported without considering species composition, and consequent changes in liana species composition is relatively unexplored. To understand the compositional change associated with disturbance, we inventoried lianas in permanent plots of the Biological Dynamics of Forest Fragments Project (BDFFP), north of Manaus, Central Amazonia, Brazil. This analysis was focused exclusively on species of the diverse genus Machaerium Pers. (Fabaceae). All lianas with DBH ≥ 2 cm were marked, measured, collected, and identified to the species level in 34 1-ha plots, distributed in continuous and fragmented forests. Density data were analyzed at three hierarchical taxonomic levels: the whole liana community, the genus Machaerium, and each species within Machaerium. At both the generic and species levels, we calculated absolute and relative density. Density (absolute and relative) was evaluated using two indicators of forest disturbance: (1) continuous versus fragmented forest, and (2) plot proximity to forest edge. We employed Generalized Linear Mixed Model with Template Model Builder for analyses. As expected, whole community liana density was positively related to forest disturbance. However, absolute density of the genus Machaerium was not affected by edge or by forest fragmentation, and consequently relative density of the genus Machaerium was reduced. Among the eight species of Machaerium, we found distinct patterns of response to disturbance. Absolute densities of M. hoehneanum and M. aureiflorum were positively affected by forest disturbance, similar to the pattern of the whole liana community, while absolute densities for M. macrophyllum and M. ferox were negatively affected. Absolute densities of the other four species (M. madeirense, M. leiophyllum, M. multifoliolatum, and M. quinata) were not affected by fragmentation indicators. The relative density of six of the eight Machaerium species was negatively affected by forest fragmentation. The variation of responses in closely related species of lianas suggests that liana species are neither uniformly nor always positively affected by forest fragmentation.