CO2 Emission Rates Were Greater in Lfh Mineral Soil Mix Than in Peat Mineral Soil Mix and Were Little Affected By CWD in Reclaimed Oil Sands Soils.

Oil sands mining related activities in northern Alberta, Canada emit large amounts of CO₂ to the atmosphere. Reclamation can sequester atmospheric CO₂ by supporting plant growth; it may also increase CO₂ emission by enhancing microbial decomposition of soil organic matter. Peat and LFH (litter, fragmented and fermenting litter and humus) are common sources of organic matter and coarse woody debris (CWD) can be an additional source of organic matter for reclamation of open-pit mined areas. This study evaluated the effects of cover soil type and CWD on CO₂ emission in the reclaimed oil sands landscape. The experimental design was a 2 (peat-mineral soil mix vs LFH) × 2 (near or away from CWD) factorial design with six replications. The study site was established between November 2007 and February 2008; six plots had peat-mineral soil mix (PMM) and another six had LFH as a cover soils; fresh aspen CWD was placed (scattered) on each plot. The CO₂ emission rates were measured near CWD (N_CWD, within 5 cm from CWD) and away from CWD (A_CWD, more than 1 m away from CWD) subplots using Hutchinson chambers at the end of July, August and September in 2012 and 2013. CO₂ emission rates were greater in LFH than in PMM at each sampling time (P<0.01). CO₂ emission rates from N_CWD were slightly greater (P>0.05) than from A_CWD and decreased over time from July to September. CO₂ emission rates were related to dissolved organic carbon (P<0.05) and nitrogen (P<0.05) concentrations and enzyme activities (P<0.05) but not with soil temperature or gravimetric water content. The net balance between CO₂ sequestration by plant growth and CO₂ emission from the soil needs to be evaluated to understand the effect of cover soil type and CWD on carbon balance in ecosystems in the reclaimed landscape.