Abstract
We have measured the levels of CO2, CH4, H2O vapor, and isoprene in areas within the Coconino National Forest (Arizona, USA) that have been burned by wildfires. Current data is compared with data obtained from the same areas four years prior. Overall, compared to soil gas levels in untouched, pristine forests, soil CO2 levels were found to be higher in the burned areas. In the case of CH4, the reverse was true, with levels of CH4 lower that those found in unburned forest areas. Compared to the same areas studied 4 years prior, greenhouse gas soil concentrations were found to be roughly similar, except for one area in which larger levels of CO2 and CH4 were observed. These results may be directly correlated with differences in soil H2O vapor concentration. Here, H2O levels that are higher may result in greater CO2 production by soil bacteria, while lower H2O levels result in higher soil CH4 relative concentrations. This result is further supported by soil gas measurements taken in the dry season of 2021, prior to the onset of the wet monsoon season. We have also obtained baseline measurements of soil and atmospheric isoprene to use for future comparisons of the levels of forest soil microbial activity.
Highlights
Forest soils play a significant role in the emission and sinking of greenhouse gases
We compare the relative concentrations of CO2, CH4, H2O vapor, and, in some cases, isoprene found in the near-surface soils of burned forests with concentrations of those same gases in pristine, unburned forests
Biomass immediately available for the soil, and microorganisms within the soil consists of dead, decomposing trees as well as the more standard leaves, needles, dead brush, and other forest litter. It is this available biomass for the soil microorganisms that may be largely destroyed during the burn
Summary
Forest soils play a significant role in the emission and sinking of greenhouse gases. Soil respiration mechanisms for both CO2 and CH4 in forests and other areas are largely the result of microbial activity in the near-surface regions of the soil. Forest wildfires are devastating structures as well as plant and animal life within the forest, and may significantly affect the microbial activity and soil respiration of gases within the soils. The destruction of forest trees, shrubs and grasses will have an effect of the food sources for the soil microbes. These effects will alter respiration from the soils for potentially years or decades after a wildfire [10,11,12]
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