Understanding processes contributing to the ecosystem flux of carbonyl sulfide and carbon dioxide in a mixed forest
Wednesday, 17 December 2014: 5:30 PM
Carbonyl sulfide (OCS) has been proposed as a valuable new measurement for understanding ecosystem carbon fluxes. Net OCS uptake is thought to be a proxy for gross photosynthetic uptake (which can’t be directly measured at large scales). However, our understanding of the OCS flux within forest ecosystems, and it's relationship to CO2, has been limited by a lack of long-term measurements of the OCS flux. Throughout 2011, the ecosystem flux of OCS was measured at a mid-latitude deciduous forest (Harvard Forest, MA, US), a site of long-term CO2 flux measurements. In order to understand the processes contributing to the seasonal ecosystem fluxes of OCS and CO2, we used the Simple Biosphere Model (SiB). This is an enzyme-kinetic model that couples the carbon cycle to the surface energy, water and radiation balance through stomatal regulation. The model has been extended to include a coupled representation of OCS uptake by leaves and soil. Here we test these parameterizations against the whole suite of ecosystem fluxes (including OCS flux) measured throughout the year. We also evaluate the effect of longer-term processes (such as phenology and soil moisture stress) on inter annual variation in ecosystem flux and OCS exchange.