Impacts on the health of large trees in Brazilian semi-deciduous seasonal forest

Large trees (LTs; diameter ≥ 50 cm) play unique ecological roles. They significantly contribute to the maintenance of forest carbon stocks, hydrological regime, nutrient cycling, and are important sources of resources for wildlife. LTs exhibit increased vulnerability to forest fragmentation, with a considerable rise in mortality rates. Therefore, investigating the health status of these individuals is important for forecasting and preventing potential collapses. In this study, we investigate the health of LTs in forest fragments of different sizes (34–690 ha) and disturbance history. The analyses were conducted in permanent plots located in six fragments of the Semi-Deciduous Seasonal Atlantic Forest in northern Paraná State, Brazil. Trees were assessed using 11 health indicators condensed into a Health Threat Index (HTI). Out of the 62 trees assessed, 60 showed signs of health threats, with the most frequent indicators being the presence of lianas tangled in the crowns and stems, as well as partial crown death. Furthermore, a trend of reduced health in LTs was observed in smaller fragments. However, this pattern may also reflect differences in disturbance history, such as selective logging, which likely increases liana colonization. Our results highlight the importance of preserving large and well-conserved forest fragments for maintaining LTs health while emphasizing the need to account for additional factors, such as forest management practices. Therefore, the preservation of large mature forest fragments, along with monitoring and implementing effective management strategies for LTs, is of utmost importance for maintaining the structure and functioning of forest ecosystems.