LAUSR

Temperate forest soils are an important sink for methane (CH4); however, disturbance through forest management and the creation of skid trails may significantly decrease soil’s ability to uptake CH4 or in some cases cause CH4 emissions. Skid trails might also be expected to show reductions in carbon dioxide (CO2) flux due to anaerobic conditions and reduced root activity. Studies to date have investigated skid trail greenhouse gas flux dynamics on experimentally created skid trails, which may not experience the full extent of traffic intensity or contain the various microsites found in actual harvested areas. We investigated variation of CH4 and CO2 fluxes based on traffic intensity, trail topography, and trail microsites in selection-managed hardwood forests in the Haliburton Highlands of Ontario, Canada. Skid trail soils showed reduced CH4 uptake, and primary and secondary trails were found to commonly be a CH4 source, especially on lower slope locations and on wheel track and trail middle ridge microsites. Skid trails also showed high CO2 emissions in the same areas. CH4 emissions on skid trails were correlated with low surface soil porosities and high soil moisture contents, which were found to occur most frequently on highly impacted trails, in low-lying areas, and in the wheel tracks and trail middle ridges. Scaling up, skid trails offset ~ 45% of CH4 uptake in untrafficked soils, an effect that should be accounted for in future greenhouse gas budgets of managed forests.