Local-scale tree community ecotones are distinct vegetation types instead of mixed ones: a case study from the Cerrado–Atlantic forest ecotonal region in Brazil

Abstract

The aim of this study was to evaluate the vegetation identity of local-scale ecotones and its importance to landscape biodiversity in a transition between savanna and forest vegetation types in Brazil. We surveyed the tree community (diameter at breast height ≥5 cm) within 25 plots of 400 m2 across three core vegetation types and two ecotones among them (totalling five vegetation types). We then evaluated similarities in species composition, community structure and phylogenetic diversity across the transitions in order to assess the relationship between the ecotones and the core areas. Ecotones were distinct floristic units with a high number of unique species and floristic and phylogenetic clustering, and hence these environments are additional vegetation types in relation to the core areas. Some species showed maximum abundance in ecotones, which harboured distinct ecological patterns, demonstrating the importance of the ecotones in the overall ecosystem. Results are related to the distribution of the species present in the regional pool across local-scale microhabitats, with ecotones being a product of a distinct environmental conditions resulting from the distinct adjacent biomes (savanna and forest), which enable the maintenance of biological diversity.

Fragmentation effects on beta diversity of fragmented and conserved landscapes: insights about homogenization and differentiation processes

“…Although ecotones are characterized as transitional areas (Gosz 1993;Risser 1995), their floristic composition was distinct from the vegetation types connected by them (results; Souza et al 2020). This result highlights the importance and singularity of these ecotone regions, which have been known as distinct vegetation units (Kark & Van Rensburg 2006).…”

“…This result highlights the importance and singularity of these ecotone regions, which have been known as distinct vegetation units (Kark & Van Rensburg 2006). Such heterogeneity may be comprehended through the observation of different ecotone scales present in the area, among biomes and among communities (Souza et al 2020). Therefore, it is a unique region strongly threatened and poorly protected, since the richness present in the non-protected areas is not completely included in PESRM.…”

“…(Odum 1953). Additionally, ecotones from PESRM have demonstrated be floristically and phylogenetically distinct vegetation type with own particularities (Souza et al 2020).…”

Tropical forests structure and diversity: A comparison of methodological choices

“…equivalent diameter) for the whole tree, combining measurements from all living stems (i.e. by-tree method; Maia et al, 2020;Mariano et al, 2020;Scolforo & Mello, 1997;Souza et al, 2020). In the by-tree method, a tree is sampled when its equivalent diameter…”

“…semideciduous and evergreen forests), minimum diameter threshold usually ranges from 4.8 to 5 cm at ~1.3 m from the ground, referring to either stems or (equivalent diameter of) trees. This is the case regardless of structural similarities between Atlantic evergreen forests and rainforests elsewhere (Caiafa & Martins, 2007;Mariano et al, 2020;Matos et al, 2020;Souza et al, 2020). Particularly for tropical dry forests, a recently released sampling protocol established a minimum diameter threshold of 5 cm per stem (Moonlight et al, 2020).…”