Post-fire soil fluxes of CO2, CH4 and N2O along the Colorado Front Range

Wildfires affect Rocky Mountain ecosystems across a wide range of spatial and temporal scales. Many of the resulting changes are greatest for environmental factors, such as substrate and microclimate that control exchanges of greenhouse gases. We investigated this link to understand how time since fire influences the cycling of these gases through ponderosa pine forests. We measured and compared trace gas flux rates between recently burned sites and topographical aspects (north- and south-facing slopes). We calculated the ability of five factors (soil temperature, soil moisture, fire severity, aspect and time since fire) to describe the variability in the flux rates. Our study revealed that carbon dioxide (CO2) fluxes were significantly different between sites; however, methane (CH4) uptake was not different between sites or aspects. Nitrous oxide (N2O) fluxes had a significant interaction between site and aspect. Using a likelihood approach, we determined the strength of support in the data for model combinations of five variables. Of these, the single variable models soil moisture, time since fire and severity best described the CO2, CH4, and N2O flux data respectively. Our data show that following a forest fire in the Colorado Front Range, >98% of the global warming potential of the measured soil–atmosphere fluxes is contributed by the soil CO2 flux.