Recent Trends in Greenhouse Gases Levels in the Soils of the Coconino National Forest

Abstract

We have taken near-surface soil measurements of the gases CO2, CH4, H2O and isoprene in several regions of the Coconino National Forest, Arizona, USA. Sets of measurements were taken both prior to the start of the seasonal monsoon season, in addition to while the monsoon season was underway. We have also compared the current monsoon season readings with readings taken at the same locations four years prior. For CO2, the relative level in the pristine forest soil is just under 3.7 percent lower than that measured in 2017, while the CO2 relative levels for the thinned and logged sites are lower by 13.5 and 5.4 percent, respectively. Even accounting for small increases in forest vegetation, these lower readings appear to be correlated to lower overall soil H2O concentrations. The pristine CH4 relative concentration in 2021 is 9.6% higher and the thinned CH4 level is 19% higher. For the logged region, the measured methane level is over 70% lower than in 2017, but still approximately triple the methane level as seen in the other forest areas. We conclude that this result also may also be correlated to lower measured H2O levels in the soils.