Unraveling intraspecific trait variation in Amazonian secondary forests: interactions among succession, soils, plant height and species strategies

Abstract Secondary forests (SFs), which dominate tropical regions and account for more than half of the total forest area, play a crucial role as carbon sinks and contribute significantly to climate change mitigation. However, our understanding of how species respond to ongoing climate change in these forests remains limited, particularly because species performance may shift across successional stages in response to changing environmental filters. Therefore, understanding the factors that influence species regeneration and drought tolerance is essential for predicting their resilience in the face of intensifying climate change. In this study, we evaluated intraspecific variation in hydraulic and anatomical traits of three abundant tree species (Eschweilera coriacea, Licania kunthiana and Tapirira guianensis) occurring in a successional gradient of SFs in the Eastern Amazon and their relationships with soil characteristics. We identified intraspecific variation both among individuals within the same plot and across different plots; however, we did not observe a consistent pattern of trait variation along the successional gradient. In some cases, successional age was associated with variation in anatomical and hydraulic traits, but these relationships were not consistent across species. In addition, soil properties were a key determinant of intraspecific variation. Our findings highlight the complexity of intraspecific trait responses in SFs and underscore the need to consider both species-specific strategies and environmental drivers when predicting forest resilience under future climate change