Environmental controls on methane consumption and carbon dioxide production in upland boreal forest soils, Thompson, Manitoba

CH{dollar}sb4{dollar} and CO{dollar}sb2{dollar} fluxes were measured in upland boreal forest soils, over the period May 16{dollar}sp{lcub}rm th{rcub}{dollar} through Sept. 16{dollar}sp{lcub}rm th{rcub}{dollar}, 1994, among a variety of vegetation and drainage characteristics. Most upland soils consumed CH{dollar}sb4{dollar}, (0.6 to {dollar}-{dollar}2.6 mg CH{dollar}sb4{dollar} m{dollar}sp{lcub}-2{rcub}{dollar} d{dollar}sp{lcub}-1{rcub}{dollar}), and produced CO{dollar}sb2{dollar}, (0.2 to 26.8 g CO{dollar}sb2{dollar} m{dollar}sp{lcub}-2{rcub}{dollar} d{dollar}sp{lcub}-1{rcub}{dollar}). CH{dollar}sb4{dollar} consumption showed no seasonal trend, however CO{dollar}sb2{dollar} flux displayed an increasing rate until late August, after which flux rates began to decrease. Differences among the sites examined showed soil temperature and organic matter content to be the primary controls in predicting seasonal mean CH{dollar}sb4{dollar} flux rates. Similarly for CO{dollar}sb2{dollar} flux, soil temperature and C content proved to be the best predictors of seasonal mean differences among the range of sites examined.; Sites could be divided into 2 categories, strong CH{dollar}sb4{dollar} consuming and CO{dollar}sb2{dollar} producing sites, Gillam Aspen, Gillam Pine, OBS Aspen, Burn Moss, Palsa Birch, and YJP Dry and weak CH{dollar}sb4{dollar} consuming and CO{dollar}sb2{dollar} producing sites, Gillam Spruce, OBS Spruce, YJP Wet, Burn Spruce and Palsa Moss. The strong flux sites all exhibited similar trends in soil characteristics as they were the warmest, driest sites with faster nutrient cycling processes and thin ({dollar}sim{dollar}2 to 10 cm) organic layers. The weak flux sites were colder, wetter, with slower nutrient cycling, and a thick organic/peat layer ({dollar}sim{dollar}20 to 50 cm). The primary visual distinction between these two groups was the presence of a Sphagnum sp. ground cover, which was characteristic of weak CH{dollar}sb4{dollar} consuming and CO{dollar}sb2{dollar} producing sites.