Abstract
Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for upland reclamation post open-pit oil sands mining in northern Alberta, Canada. Coarse woody debris (CWD) can be used to regulate soil temperature and water content, to increase organic matter content, and to create microsites for the establishment of microorganisms and vegetation in upland reclamation. We studied the effects of CWD on soil microbial community level physiological profile (CLPP) and soil enzyme activities in FMM and PMM in a reclaimed landscape in the oil sands. This experiment was conducted with a 2 (FMM vs PMM) × 2 (near CWD vs away from CWD) factorial design with 6 replications. The study plots were established with Populus tremuloides (trembling aspen) CWD placed on each plot between November 2007 and February 2008. Soil samples were collected within 5 cm from CWD and more than 100 cm away from CWD in July, August and September 2013 and 2014. Microbial biomass was greater (p<0.05) in FMM than in PMM, in July, and August 2013 and July 2014, and greater (p<0.05) near CWD than away from CWD in FMM in July and August samplings. Soil microbial CLPP differed between FMM and PMM (p<0.01) according to a principal component analysis and CWD changed microbial CLPP in FMM (p<0.05) but not in PMM. Coarse woody debris increased microbial community functional diversity (average well color development in Biolog Ecoplates) in both cover soils (p<0.05) in August and September 2014. Carbon degrading soil enzyme activities were greater in FMM than in PMM (p<0.05) regardless of distance from CWD but were not affected by CWD. Greater microbial biomass and enzyme activities in FMM than in PMM will increase organic matter decomposition and nutrient cycling, improving plant growth. Enhanced microbial community functional diversity by CWD application in upland reclamation has implications for accelerating upland reclamation after oil sands mining.
Highlights
The Athabasca oil sands region in northern Alberta, Canada, is the largest single oil sands deposit in the world with an estimated 1.6 trillion barrels of bitumen, a low quality crude oil mixed with sands and water [1]
Soil pH, total C, and total N were significantly affected by cover soil type but not by distance from Coarse woody debris (CWD) or their interactions, and they were higher in peat mineral soil mix (PMM) than in floor mineral soil mix (FMM) (Table 1)
The two cover soils (FMM and PMM) commonly used for oil sands reclamation had different microbial community level physiological profile (CLPP), microbial biomass, and enzyme activities associated with contrasting soil properties and vegetation cover originated from different ecosystems
Summary
The Athabasca oil sands region in northern Alberta, Canada, is the largest single oil sands deposit in the world with an estimated 1.6 trillion barrels of bitumen, a low quality crude oil mixed with sands and water [1]. A common reclamation practice in this region is returning disturbed land to upland boreal forests. Substrates, such as overburden materials or tailing sands, are not suitable for plant growth due to lack of nutrients, high salinity, and high concentrations of toxic materials including naphthenic acids, polycyclic aromatic hydrocarbons, phenolic compounds and trace metals, and approximately 30 cm of cover soils are applied over a substrate to support plant growth to supply nutrients and to improve soil properties [3,4]. Characterizing and understanding microbial community and enzyme activity are important for successful land reclamation after oil sands mining
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