Extirpation of large-seeded seedlings from the edge of a large Brazilian Atlantic forest fragment

In this study we assessed the seedling assemblages of a large fragment of the Atlantic forest to test 2 hypotheses: (1) seedling abundance and richness are lower in the forest edge (0–200 m) than in the forest interior (>250 m); and (2) large-seeded seedlings (seeds >1.5 cm) are the main group affected by edge creation. The study was car ried out at the Coimbra forest, an old, 3500-ha fragment surrounded by sugar cane plantations in northeast Brazil. The seedling survey was based on 200-m-long transects along which 420 plots of 1-m2 were set up per habitat and per season (dry and rainy). Within the plots, all shrub, tree, palm, and liana species seedlings ≤ 50 cm tall were counted and classified to morphospecies level. A total of 13 208 seedlings were recorded in the whole survey. At plot level, forest edge and interior showed similar scores for both average seedling density (4.7–11.2 seedlings·m−2) and richness (2.8–5.1 species·m−2) irrespective of season. At community level, however, scores for total species richness were 4.8–17.9% lower in forest edge plots than in those of the forest interior, depending on the estimator used. Moreover, large-seeded species accounted for 2.3–2.7% of all species recorded in forest edge plots, yet this group reached 13.1–14.9% in forest interior plots. As a consequence, the forest edge housed between 166 and 262 large-seeded seedlings·ha−1, whereas the forest interior housed 5 952–6 047 large-seeded seedlings·ha−1. Our results suggest that old forest edges hold biased and impoverished assemblages of seedlings, particularly in terms of large-seeded trees.