Resprouting drives successional pathways and the resilience of Caatinga dry forest in human-modified landscapes

Impoverished woody seedling assemblages and the regeneration of Caatinga dry forest in a human‐modified landscape

“…Moreover, leaf‐cutting ants respond positively to human disturbances in this landscape, reducing seedling abundances across extensive foraging areas (Knoechelmann et al, 2020; Siqueira et al, 2017, 2018). As the seedling bank declines in response to human disturbances, forest regeneration becomes more dependent on adult resprouting, a common mechanism across dry forests (Murphy & Lugo, 1986; Sampaio et al, 1993), and a reasonable explanation for the current dominance of P. moniliformis adults in the Catimbau National Park, as it resprouts vigorously (Barros et al, 2021; Souza et al, 2019).…”

“…By assuming that our snapshot captured more than the last recruited seedling cohort (usually from the last rainy season) and included a significant proportion of species attending the assemblages (see Figure S1), our findings indicate that: (1) seedling assemblages represent a limited and sensitive source (i.e., negatively affected by external factors) for adult recruitment and will likely have a limited impact on the structure of future adult assemblages; (2) species recruiting via seedlings are probably the ones able to persist in the system for an extended period of time (e.g., from the previous rainy season or emerged after irregular rain periods) with limited growth and take long periods of time to establish new adult individuals (i.e., slow forest dynamic); and (3) other regeneration mechanisms, such as adult resprouting and vegetative propagation may play a significant role in Caatinga forest regeneration (see Barros et al, 2021; Sampaio et al, 1993; Vanderlei et al, 2021), as observed in different dry forests (Bond & Midgley, 2001; Vieira & Scariot, 2006).…”

“…It is worth mentioning the proliferation of disturbance‐adapted species (Ribeiro et al, 2015; Rito, Tabarelli, et al, 2017; Siqueira et al, 2017, 2018) and taxonomic changes in response to wood extraction, as we observed in this study. Changes in physical conditions (i.e., increased habitat desiccation) and selection of resprouting species have been proposed as key drivers for community‐level responses to chronic human disturbance in the Caatinga dry forest (Arnan et al, 2018; Barros et al, 2021; Ribeiro et al, 2015; Rito, Arroyo‐Rodríguez, et al, 2017; Rito, Tabarelli, et al, 2017). In our focal landscape, introduced goats have been reported to reduce the biomass and diversity of herb assemblages (Menezes et al, 2020), with a combination of shifting cultivation and goat pressure as the anecdotal drivers for the establishment of assemblages dominated by unpalatable perennial herbs such as Herissantia crispa (Malvaceae).…”

“…Water availability in the Caatinga is highly variable across space (i.e., there is a strong landscape‐scale rainfall gradient in our study area) and between seasons (dry and rainy), with frequent and severe (1‐ to 3‐year long) droughts (Sampaio, 1995). However, the Caatinga woody flora exhibits: (1) at least three plant syndromes associated with water and/or nutrient use, including two associated with dry habitats (i.e., softwood species with soft leaves and hardwood species with either conservative or acquisitive leaves; Pinho et al, 2019); (2) high intraspecific leaf‐trait plasticity (Sfair et al, 2018); and (3) distinct strategies to deal with stresses such as water scarcity (Barros et al, 2021; Pinho et al, 2019; Sfair et al, 2018; Zorger et al, 2019). Thus, the Catimbau flora has been considered functionally diverse, which may be essential to adapt to future climate/land‐use changes.…”

“…These pressures on seedlings can favor species able to resprout, with forest regeneration marked by this mechanism (Barros et al, 2021; Murphy & Lugo, 1986; Vanderlei et al, 2021; Vieira et al, 2006). However, the combined effects of both water availability and chronic anthropogenic disturbances on seedlings remain poorly investigated, despite their potential impacts on forest regeneration and dynamics in human‐modified landscapes (see Barros et al, 2021; Souza et al, 2019; Vanderlei et al, 2021).…”