Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient

Abstract

We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.

Taxonomic and functional divergence of tree assemblages in a fragmented tropical forest

“…, , Orihuela et al. ). The present study helps to fill this gap of information by demonstrating, for the first time, that there is a significant taxonomic and functional divergence of tree assemblages in edge‐affected forests (i.e., forest fragments and forest edges) compared with old‐growth forest interior areas within a severely deforested landscape of the Brazilian Atlantic forest.…”

Tree Component Demography in an Upper Montane Mixed Ombrophilous Forest Under Chronic Anthropogenic Disturbances

“…Considering the studies published by Orihuela et al (2015) and Reis et al (2014), one can indeed inferred that MOF is mainly formed by a group of stresstolerant species with Araucaria angustifolia as one of its representatives. While Orihuela et al (2015) highlight MOF's history of expansion over open areas so as to favor the occurrence of light-demanding and disturbancetolerant species, Reis et al (2014) emphasize the influence of indigenous cultures which activities cause chronic disturbances so as to also favor species adapted to disturbances. In the same way as Mello and Peroni (2015) highlight the conservation value of the Caívas (ecotypes from a cultural landscape in the north of the State of Santa Catarina, Brazil), our results thus indicate that the traditional use of forest remnants can also be considered as an alternative form of soil use.…”

Edge effect on the spatial distribution of trees in an Araucaria Rainforest fragment in Brazil

“…It is also interesting to observe that some studies have analyzed the Araucaria Forest expansion system and have found that this forest type expands its limits by promoting certain species, as pioneers with fast development over the edge limits (Carlucci et al 2011). Because of the presence of a large number of species well adapted to this expansion process, the Araucaria forest can be considered less susceptible to changes in the environment such as the forest fragmentation (Orihuela et al 2015).…”

“…The distance of edge effect cannot be generalized, since this factor is different for each variable response considered, ranging from zero to more than 400 m into the forest . Also, each ecosystem has a distinct response according to the forest type (Orihuela et al 2015), surrounding matrix (Harper et al 2005) and edge age (Laurance et al 2011). In Araucaria Rainforest region Fontoura et al (2006) observed approximately 50 m of edge impact on wood species, and noticed that a great number of species are just found close to the edge, while some other species are not found until some minimum distance from the edge.…”

“…Because of that, it is important to study the impacts of the forest fragmentation to create plans to maintain the remaining biodiversity. There have been a number of studies carried out in the Araucaria Rainforest about the edge effect on forests, relatives to edge effect on vascular epiphytes (Bianchi & Keresten 2014), changes in plant diversity and phytosociology along the edge distance (Fontoura et al 2006;Ferreira et al 2016;Orihuela et al 2015), seed predation (Baldissera & Ganade 2005) and changes in forest structure (Malchow et al 2006).…”