ANAEROBIC AND AEROBIC CO2 EFFLUX RATES FROM BOREAL FOREST CONIFER ROOTS AT LOW-TEMPERATURES

The efflux of CO2 from roots of Pinus banksiana Lamb., Pinus contorta Dougl., Picea glauca (Moench) Voss, Picea mariana (Mill.) B.S.P., and Larix laricina (Du Roi) K. Koch were measured under anaerobic and aerobic conditions at 5, 15, and 25-degrees-C. Picea mariana showed an anaerobic to aerobic CO2 efflux ratio that was significantly higher than all other species at 5-degrees-C. Larix laricina showed higher levels of anaerobic and aerobic CO2 efflux rates than the other four species. These data suggest that Picea mariana roots have higher overall increases in fermentation rates with onset of anoxia at 5-degrees-C, and L. laricina roots have high fermentation and respiration rates at 5-degrees-C. These features may be indicative of metabolic adaptations to cold, flooded peatland soils of Canadian boreal forests. A redox dye test showed O2 diffusion from roots of Pinus spp. and L. laricina at each temperature level. Thus these species have some ability to transport O2 to root tissues and sustain limited respiration under anaerobic conditions. Black and white spruce did not show any O2 diffusion from roots at any temperature.