Effect of precipitation and elevated temperature on soil greenhouse gas fluxes in multiple ecosystems

Carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) are powerful greenhouse gasses driving global change. As global atmospheric concentrations of CO₂, CH₄, and N₂O increase, in-situ terrestrial flux measurements of these gasses are an important part of quantifying sources and sinks as well as determining positive or negative feedbacks. We assessed responses of soil fluxes of CO₂ (soil respiration), CH₄, and N₂O to elevated temperature and altered precipitation treatments along the C. Hart Merriam Elevation Gradient Transect in Northern Arizona during a monsoon season. We found significant increases in soil respiration and N₂O efflux, and a decrease in CH₄ oxidation (uptake) in response to increasing elevation and precipitation. We found that warming of ~3 °C in the mixed conifer ecosystem removed temperature limitations on production of N₂O and CO₂, and that CH₄ oxidation was not temperature dependent. We also found that altering precipitation within ecosystems influenced fluxes of all three gasses. As soil moisture increased, soil respiration and N₂O efflux increased, while CH₄ oxidation appeared to become limited by diffusion of CH₄ and/or oxygen. Overall, we found that the increase in temperature and precipitation predicted for Northern Arizona during the monsoon season will result in an increase in soil respiration and N₂O production and a decrease in CH₄ oxidation by soils. These changes constitute a positive feedback for all three gasses in response to the climatic changes caused by increasing atmosphere concentrations of CO₂, N₂O, and CH₄.