Observations of carbonyl sulfide (OCS) can be used to estimate stomatal conductance in forest ecosystems. The largest global flux of OCS is uptake in plant leaves when stomata are open, following a parallel biochemical pathway to CO2. The major sources of OCS are geographically disparate from plant uptake: oceans and specific industries. OCS is a ubiquitous atmospheric gas with a background concentration of roughly 0.5 ppb. Decreases in the background are usually associated with uptake via stomata, integrated over the time period of an airmass' contact with the forest and with small contributions from soils, mosses, and interactions with leaf litter. This project will observe OCS concentrations from the hardwood tower to compare with instantaneous solar induce fluorescence measurements as a two-pronged effort to understand forest functioning. To understand the contribution of the forest understory, OCS flux observations will be made on understory elements with non-destructive long term soil chambers and with an IR camera.