Ozone Susceptibility of Tropical Tree Species

Tropical forests account for approximately 60% of global terrestrial photosynthesis, yet their function into the future may be compromised by rising ground-level ozone (O₃) pollution. Although O₃ is known to impair plant productivity, the physiological mechanisms underlying interspecific variation in O₃ susceptibility-especially among tropical trees-remain poorly resolved. Here we exposed 11 tropical tree species to a gradient of O₃ concentrations using open-top chambers and quantified whole-plant biomass responses alongside key plant functional traits. Species varied markedly in O₃ susceptibility, with relative growth reductions best explained by differences in plant mass per unit leaf area (PMA). Contrary to expectations, antioxidant capacity and leaf mass per area were not predictive of O₃ susceptibility of tropical tree species. These findings indicate that fundamental structural traits may mediate tropical tree responses to O₃, and that species with higher PMA exhibit greater resilience-within the experimental framework employed here. Our results help inform trait-based risk assessments and support the need for improved representation of O₃ impacts in models of carbon cycling in tropical forests.