Health and mortality of large trees in Semi-deciduous Atlantic Forest fragments

Abstract

In tropical forests, large trees (LTs; those with a diameter ≥50 cm), can suffer significant abundance decline, especially near the edges of fragments. However, the mechanisms involved with this decline remain poorly understood. The objective of this study was to investigate edge effects on the health of LTs over a four-year interval, and identify the factors driving their mortality. The study was conducted in eight Semi-deciduous Seasonal Atlantic Forest fragments in the northern Paraná state, Brazil. The health of LTs was evaluated along an 0–250 m, edge-interior gradient using 11 indicators compiled into a Health Threat Index (HTI). Four sites had LT health assessed twice (2019 and 2023). A higher incidence of health threats was observed in the first 50 m from the forest edge, with a reduction in the frequency of these indicators with increased distance from the edge. This pattern was stronger in the largest fragment. Among the four re-sampled fragments, three maintained stable HTIs, while one exhibited a decline in LT health. The main indicators associated with LT mortality were liana infestation and the presence of dead crown portions. Liana cutting and other management measures should be tested in order to improve conservation of such important organisms.