Forest fragmentation drives Atlantic forest of northeastern Brazil to biotic homogenization

Abstract

Aim To examine whether the tree flora of the Atlantic forest of northeastern Brazil has experienced detectable taxonomic homogenization via the proliferation of native pioneer species in response to habitat loss and fragmentation. Location Biotic homogenization (BH) was examined across the Atlantic forest of northeast Brazil, i.e. a 56,000 km2 piece of tropical forest and a distinct centre of species endemism in South America. Methods We assessed a dataset consisting of 5122 tree records and compared the similarity of tree floras from 12 semi‐natural sub‐regions of the Atlantic forest between two time periods: pre‐1980 (plant records between 1902 and 1980), and post‐1980 (between 1981 and 2006). To understand the mechanisms leading to BH (1) tree floras were ordered (via non‐metric multidimensional scaling – NMDS) by date (pre/post 1980) based on species occurrence and frequency, (2) NMDS axes were regressed against the proportion of those species that increased their occurrence post‐1980 (i.e. the winner species), and (3) patterns of geographic distribution and frequency of particular life‐history traits were examined across winner species and a control group. Results Tree floras across the Atlantic forest became c. 20–40% more similar to each other post‐1980, but patterns of species similarity were also influenced by between‐plot geographical distance. NMDS ordination clearly segregated pre‐ and post‐1980 floras with a clear signal of floristic convergence. Furthermore, winner tree species were largely composed of short‐lived and small‐seeded pioneer species that exhibit wide geographic distributions. Main conclusions Our results suggest that tropical forest biotas are susceptible to taxonomic homogenization (i.e. increasing levels of similarity) in the context of severe human‐disturbance via the proliferation of particular groups of native species comprised mainly by ecologically‐plastic, generalist species. We are thus extending the concept of homogenization to address and highlight a pervasive biological shift in the structure of tropical forest communities currently taking place across hyper‐fragmented landscapes.

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

“…Results obtained here thus reinforce the idea that chronic anthropic disturbances potentially influence both species richness -as once noted by Lôbo et al (2011) -, which favors the process of biological homogenization, and the successional trajectory of forests, by either limiting or slowing down the process of ecological succession (Clark and Covey, 2012;Zamorano-Elgueta et al, 2014;ArroyoRodríguez et al, 2015). In long term, a floristically more homogeneous forest is thus expected, consisting mainly of functional groups (light-demanding climax) and species (e.g.…”

Litterfall Assessement in a Fragment of Secondary Tropical Forest, Ibiúna, Sp, Southeastern Brazil1

“…Tropical forests present an exuberant tree, shrubs and palm flora that depend on the balance of the nutrient cycling (PINTO et al, 2009), which highlights the importance of the decomposition in the system. The Atlantic forest is fragmented throughout its extension due to an intense history of deforestation and human settlements (LÔBO et al, 2011;LAPOLA et al, 2014). Currently, there are about 8% of the original size of the forest, whereas if secondary forest areas are included, this value rises to approximately 17% (RIBEIRO et al, 2009).…”

Habitat fragmentation and the future structure of tree assemblages in a fragmented Atlantic forest landscape

“…edge-affected habitats) have provided key evidence on the potential effects imposed by habitat loss and fragmentation, particularly the establishment of forest edges immersed into openhabitat matrices (see reviews in Tabarelli et al 2010b andJoly et al 2014). Impoverished tree assemblages are dominated by some pioneer species, which tend to proliferate from local to regional scales (Lôbo et al 2011;Tabarelli et al 2010a). Proliferation of pioneer and light-demanding species (successional species, sensu Laurance et al 2006b) parallels population collapses and extirpations of species in several ecological groups belonging to the old-growth flora, such as large-seeded ) and emergent species , and those with specialized floral biology (Girão et al 2007;Lopes et al 2009).…”