Foliar methane and nitrous oxide fluxes in Salix bebbiana respond to light and soil factors

Foliar exchange of methane and nitrous oxide is a significant yet poorly understood component of global greenhouse gas budgets. To address this knowledge gap, we investigated foliar methane and nitrous oxide fluxes in <i>Salix bebbiana</i>, under varying light conditions (0-2000 μmol·m^-2·s^-1), soil aeration, and nitrogen availability, manipulated via biochar incorporation and nitrogen additions. Using rapid spectroscopic gas analysers, we observed consistent net foliar methane oxidation and nitrous oxide emission across all light conditions, demonstrating saturating light response patterns. Maximum flux rates were significantly more sensitive to soil conditions than carbon dioxide or water vapour exchange. Analysis revealed foliar methane and nitrous oxide fluxes overwhelmingly regulated by internal leaf processes like xylem transport, with modulation by external light intensity. These predictable light-response patterns provide a basis for scaling leaf-level methane and nitrous oxide fluxes, enhancing accuracy in predicting biogenic greenhouse gas fluxes within ecosystem and biosphere models.