Early eco‐physiological responses in a direct seeding experiment: a non‐destructive approach reveals contrasted strategies in tropical tree species

Abstract Introduction Conservation physiology is a valuable tool for addressing the major challenges of tropical restoration programs. One key issue is the need for non‐destructive methods to study the functional responses of highly threatened species in order to minimize impacts on natural populations. Additionally, the eco‐physiological responses of rare native species in tropical island forests remain poorly understood, particularly in early life stages. As indirect, readily and non‐destructive measurements, physiological soft traits (PST) offer a promising, yet underutilized, approach for incorporating eco‐physiological measurements into restoration operations. Objectives In this study, we develop a conservation physiology framework based on non‐destructive measurements of leaf PST to assess in situ the early eco‐physiological responses of 17 high‐conservation‐interest species. Methods We finely characterized each species' environment through soil analyses and hemispherical photography and measured leaf PST using a Dualex 4 (FORCE A, Orsay, France), namely chlorophyll content, flavonoids index, and adaxial/abaxial flavonoids ratio. Linear mixed models (LMMs) were used to quantify species' functional responses to canopy openness (CO), and a principal component analysis was performed from LMMs coefficients to characterize seedling ecological strategies. Results Our results revealed strong interspecific variability in leaf PST responses across the CO gradient. We identified establishment strategies based on species' light affinity in early life‐stages. Conclusions Our results provide new insights into the ecological strategies of tropical tree species at the seedling stage. These findings highlight the value of a conservation physiology framework in improving species selection for ecological restoration. We emphasize the importance of understanding species‐specific responses to environmental variation to enhance restoration success.