Determining the Drivers of Redox Sensitive Biogeochemistry in Humid Tropical Forests

The availability of soil oxygen (O2) and associated redox dynamics are key drivers of carbon and nitrogen cycling and greenhouse gas emissions in tropical forests. However, few studies have measured soil oxygen availability, and even fewer have related this to greenhouse gas fluxes over time and space. Improved mechanistic understanding of the relationship between soil O2 concentrations and greenhouse gas dynamics will improve Earth systems models. In this study, we are using field and laboratory experiments in the Luquillo Experimental Forest, Puerto Rico, to develop a mechanistically derived redox component for the Community Land Model (CLM4). We are using empirical and modeling efforts to improve the prediction of carbon, nitrogen, and phosphorous cycling and greenhouse gas dynamics in space and time. Our research tests the following hypotheses: 1) Soil O2 concentrations vary as a function of soil texture, slope position, and rainfall in humid tropical forests; 2) The spatial and temporal dynamics of soil O availability can be used to predict patterns in redox sensitive biogeochemical processes; and 3) Hot spots and hot moments in greenhouse gas fluxes are derived primarily from high substrate availability and secondarily from soil O2 availability.