Organic capping type affected nitrogen availability and associated enzyme activities in reconstructed oil sands soils in Alberta, Canada

Organic materials applied in land reclamation play a key role in the development of ecosystem properties and functions. Peat mineral soil mix (PMM) and LFH (identifiable litter (L), fragmented litter (F) and humus (H)) mineral soil mix (LFH) are commonly used organic amendments for oil sands reclamation in northern Alberta. These materials have contrasting soil properties, with organic matter in LFH more decomposed and having a lower carbon-to-nitrogen (C:N) ratio than that in PMM. We quantified the effects of LFH and PMM capping material on N availability and enzyme activities during early ecosystem development in the oil sands region. Monthly samples were taken from 0 to10 and 10 to 20 cm layers from June through October in 2011 and 2012. The N availability and activities of soil enzymes including beta-1,4-N-acetyl glucosaminidase (NAGase), urease, arylamidase and protease were measured. In-situ N availability was measured using plant root simulator (PRSTM) probes. Repeated measures ANOVA indicated that N availability and NAGase, arylamidase and protease activities were greater in LFH than in PMM and were affected by time of sampling. These differences were attributed to the lower C:N ratio in LFH than in PMM. We found greater N availability and enzyme activities in the fall than in the summer in both years. These differences were likely caused by fresh labile C inputs through root exudates and litter fall during fall that induced greater enzyme activities and led to greater N mineralization despite the potential limitation by the lower fall temperature. Overall, the greater N availabilities and enzyme activities in LFH suggest that LFH would be a better soil capping material than PMM for early ecosystem development in oil sands reclamation. (C) 2014 Elsevier EN. All rights reserved.