Xylem anatomical traits and size shape time-dependent survival patterns of tree species in an Amazonian secondary forest

Tree mortality is a key process shaping species diversity and carbon dynamics during natural regeneration. Understanding how intrinsic functional traits interact with environmental drivers to modulate mortality risk is essential for predicting forest trajectories. Here, we evaluated how xylem anatomical traits related to water transport and tree size influence the survival dynamics of biomass-dominant tree species in an eastern Amazonian secondary forest, and whether climatic water‐deficit variables modulate these relationships over time. We applied Cox proportional hazards models with time‐dependent effects to long‐term census data, incorporating species‐level wood density (WD), vessel grouping (VG), specific hydraulic conductivity (Ks) and individual diameter at breast height (DBH). Functional differentiation between species in the functional space across species was assessed using a principal component analysis (PCA) associated with a trait probability density (TPD) framework. Also, we stratified models by census period and related baseline cumulative hazard estimates to maximum cumulative water deficit (MCWD) and vapour pressure deficit (VPD). Higher WD and higher VG were associated with a progressive reduction in mortality risk through time, whereas higher Ks showed a positive and time‐independent association with mortality risk, suggesting that species with greater hydraulic efficiency may experience higher vulnerability to mortality. Larger trees also showed lower mortality risk. Functional space analyses revealed substantial overlap among species, indicating a continuum of strategies rather than discrete functional groups. Species associated with lower mortality risk occupied different regions of the functional space, suggesting that alternative combinations of anatomical traits and tree size may contribute to survival through distinct functional pathways. We found no significant direct relationship between baseline cumulative hazard and climatic water‐deficit variables (MCWD and VPD), suggesting that climate effects may operate indirectly or through delayed demographic responses rather than as immediate drivers of mortality. Together, our results highlight the importance of coordinated variation in xylem traits and tree size for understanding mortality dynamics in secondary Amazonian forests. Graphical abstract. Schematic representation of the main findings of this study showing how xylem anatomical traits and tree size influence mortality risk across 16 species in an Amazonian secondary forest. Along forest succession, mortality risk is associated with functional traits related to hydraulic efficiency, xylem organization, mechanical support, and tree size. Higher theoretical specific hydraulic conductivity (Ks) is associated with increased mortality risk, whereas larger stem diameter at breast height (DBH), greater vessel grouping (VG) and higher wood density (WD) are associated with reduced mortality risk. The xylem cross-section illustrates the anatomical basis of these functional traits, highlighting their role in mediating tree survival during secondary forest succession.