Seasonal Evolution of Canopy Stomatal Conductance for a Prairie and Maize Field in the Midwestern United States from Continuous Carbonyl Sulfide Fluxes

Abstract

There are inherent challenges in scaling stomatal conductance (g (Formula presented.)) from leaf to canopy particularly over seasonal time scales when species distribution and canopy structure evolve. We address this gap using carbonyl sulfide (OCS) and CO (Formula presented.) fluxes from a predominantly C3 prairie and C4 maize field in the midwestern United States. The g (Formula presented.) derived from OCS fluxes captured a transition in the stomatal limitation on gross primary productivity (GPP) through the growing season as well as seasonally persistent g (Formula presented.) dynamics such as temperature optimum and a positive response of nighttime g (Formula presented.) to vapor pressure deficit. Near the termination of the prairie growing season, we observed a decrease in the relative OCS to CO (Formula presented.) flux that we hypothesize emerged from a rising contribution of C4 plants to productivity. The results show how plot-scale OCS and CO (Formula presented.) fluxes can be used as a trace gas diagnostic for transitions in the limiting factors for community GPP.