We used these information to assess the structure, composition, and diversity of woody seedling assemblages across 19 forest stands in a human-modified landscape of Caatinga dry forest, assessing the role played by rainfall, aboveground biomass, and chronic anthropogenic disturbances (i.e., livestock grazing pressure and wood extraction) as assembly forces. We quantified a large set of community-level attributes including functional traits related to water availability, physical protection, and survival success. We recorded a total of 544 seedlings from 59 species.

The mean annual rainfall of each forest stand was obtained from the WorldClim repository (www.worldclim.org), with rainfall data resolution of 30 arc seconds (equivalent to 1 km). Mean annual rainfall ranged from 510 mm to 940 mm. Aboveground biomass was obtained from Souza et al. (2019). We adopted two chronic anthropogenic indices from Arnan et al. (2018) that integrate indirect measures of geographical (i.e., proximity to houses and roads) and socio-ecological metrics (i.e., number of people, livestock, and firewood use), and direct field measures (i.e., goat and cattle dung, wood extraction) for each forest stand. The indices are the 1) wood extraction index, including field measurements of live and firewood collection and use, and (2) livestock pressure, including data on livestock dung, trail length, which reflects the trampling and other physical damage by cattle and goats (see Arnan et al. 2018 for detailed information).

Seedling assemblages were recorded across 19 0.1-ha (20 m × 50 m) old-growth forest stands that form part of the Catimbau Long-Term Ecological Research project (www.peldcatimbau.org). Stands are separated by a minimum distance of 2 km and spread over 214 km². To assign a plant as a seedling, we dug each plant with height ≤ 50 cm and collected the individuals that (1) did not display any reproductive organs (i.e., flower buds, flowers, or fruits) and (2) were not root suckers or sprouts (i.e., connected to root buds or sprouting stems). All the seedlings within each of the 19 forest stands were collected during two months during the rainy season of 2018 (July-August).

The traits were measured from seedlings collected in 19 50 m x 20 m (0.1 ha) forest stands in a dry forest. All the seedlings below 50 cm of height were collected and traits measured in the laboratory. Surveys were restricted to woody plants species.

Eight functional leaf traits were measured: (1) leaf area (LA, cm²); (2) specific leaf area (SLA, the ratio of leaf area to leaf dry mass, m²/kg); (3) leaf dry matter content (LDMC, the ratio of leaf dry mass to fresh mass, mg/g); (4) leaf thickness (Lth, mm); (5) leaf succulence (LS, the ratio of leaf water content to leaf area, mg/cm²); (6) leaf compoundness (LC, 0 - simple leaves; 1 - compound leaves); (7) spinescence (Spin, 0 - absent, 1 - present); (8) presence/absence of trichomes (Trich, 0 - absent, 1 - present). The collected data of traits 1-8 were collected in the field for each individual according to Pérez-Harguindeguy et al. (2013).