What can natural edges of gallery forests teach us about woody community performance in sharp ecotones?

Changes in tree size, not species diversity, underlie the low above‐ground biomass in natural forest edges

“…As we did not find higher abundances of co‐occurring tree species between habitats, the differences in tree size are most likely to underlie edge effects on AGB. de Oliveira Coelho (2016), in the same sites, showed a sharp reduction in specific tree sizes even for conspecific tree stems only 10 m apart from the immediate forest edge toward the forest interior. Two non‐exclusive hypotheses can explain smaller trees in edges as compared to interiors.…”

“…Lastly, we ran a paired Student's t test to test the hypothesis that the DBH, height, and abundance of shared species differ between edges and interiors (sampling units were the species averages in each site). We used the vegan package to perform the PERMANOVA (Oksanen et al, 2017), the lme4 package to fit mixedeffect models (Bates et al, 2015), the priceTools package to compute CAFE components (Kremer, 2020), and the agricolae package to run ANOVA and post-hoc tests (de Mendiburu, 2017). We performed all analyses in the R environment (R Core Team, 2017), and the full data are made available in Appendix S4.…”

“…This can occur when a given habitat is more limiting than another to any given ecosystem function. Natural edges are usually more stressful habitats than interiors in terms of exposure to natural hazards such as wildfires, desiccation, and limitation of soil nutrients (Van den Berg & Santos, 2003; de Oliveira Coelho et al, 2016; Bragion et al, 2018; Nunes et al, 2018; Silva et al, 2019). Soil fertility and moisture increase toward interiors (near to the stream’s edge) due to topographical effects.…”

“…Unlikely being anthropogenic forest edges, gallery forest edges could be considered ancient edges, formed centuries to millennia ago. These forests are very species‐rich and harbor an important fraction of plant diversity of the Cerrado biome (de Oliveira Coelho et al, 2016; Bragion et al, 2018; Silva et al, 2019). The climate is tropical wet (Cwa, Köppen classification) with a mean annual rainfall of 1,460 mm and a temperature of 20.4°C, with a dry winter (Jun–Sep) and wet summer (Dec–Mar; Dantas, Carvalho & Ferreira, 2007).…”

“…They are common in the Brazilian savannas (“ Cerrado ”), a global biodiversity hotspot (Myers et al, 2000). These gallery forests form a natural ecotone with grasslands or savannas, thus forming natural forest edges (Silva et al, 2008) differing from the core of the gallery forests (i.e., interiors) in terms of structure, composition, and dynamics (Van den Berg & Oliveira‐Filho, 1999; Bragion et al, 2018), but yet can harbor a great diversity of tree species (de Oliveira Coelho et al, 2016). By now, we know that AGB decreases toward the edges of gallery forests (Nunes et al, 2018; Silva et al, 2019; Deziderio Santana et al, 2021), in a way very similar to anthropogenic forest fragments (Laurance et al, 2002), even though the alpha diversity of gallery forest edges and interiors seems similar (Van den Berg & Oliveira‐Filho, 1999; Van den Berg & Santos, 2003).…”