Carbon, nitrogen and phosphorus release from peat and forest floor-based cover soils used during oil sands reclamation

Abstract

Reclamation practices in the oil sands region of Alberta involve the reconstruction of soil profiles using a combination of salvaged mineral substrates and organic-matter-rich surface materials, including peatmineral mix (PM) and forest floor -mineral mix (FFM). The successful re-establishment of vegetation on reclaimed sites is for a large part dependent on the nutrients these materials can provide. Hence, the overall objective of this study was to compare carbon (C), nitrogen (N), and phosphorus (P) release rates from PM and FFM materials used to cap reconstructed sandy soils. A 325 d laboratory incubation was conducted to measure these rates. The two materials released comparable amounts of N on a per kilogram of soil basis (111-118 mg N kg −1 ). However, when results were normalized based on each material's organic C content, N release was six times greater for FFM than for PM, in accordance with results of previous studies. In addition, overall C mineralization and P release rates were over one order of magnitude higher with FFM than with PM. As opposed to N, however, P release seemed to be controlled more by abiotic processes than by organic matter mineralization. While the FFM material overall released more N and P, it also degraded faster; in comparison, PM may provide a smaller but more stable release of N.Key words: mineralization, nitrogen, organic matter, phosphorus, soil reclamation.Résumé : Les méthodes de restauration du sol dans la région des sables bitumineux de l'Alberta supposent la reconstitution du profil pédologique au moyen de substrats minéraux récupérés et d'un matériel de surface riche en matière organique, notamment un mélange de tourbe et de minéraux (TM) et un autre de couverture morte et de minéraux (CMM). Une bonne végétalisation des sites restaurés dépend dans une large mesure des oligoéléments que procurent ces matériaux. C'est pourquoi l'étude avait pour objectif général de comparer le taux de libération du carbone (C), de l'azote (N) et du phosphore (P) par le TM et le CMM employés pour rebâtir les sols sablonneux. Les chercheurs ont mesuré ces taux en procédant à une expérience d'incubation de 325 jours en laboratoire. Les deux matériaux libèrent une quantité comparable de N par kilo de sol (111 à 118 mg de N kg −1 ). Cependant, quand on normalise les résultats d'après la concentration de C organique de chaque mélange, on constate que le CMM libère six fois plus de N que le TM, ce qui concorde avec les résultats des études antérieures. D'autre part, la minéralisation du C et le taux de libération du P du CMM dépassent ceux du TM de plus d'un ordre de grandeur. Contrairement à l'azote, le taux de libération du P semble contrôlé par des mécanismes abiotiques et non la minéralisation de la matière organique. Même si le CMM libère généralement plus de P et de N, ce matériau se détériore plus vite. Le TM, en revanche, pourrait libérer moins de N, mais de manière plus stable. [Traduit par la Rédaction] Mots-clés : minéralisation, azote, matière organique, phosphore, restau...

Effects of Stockpiling and Organic Matter Addition on Nutrient Bioavailability in Reclamation Soils

“…Studies on peat soils (Kaal et al, 2007; Barkovskii et al, 2009; Perez‐Rodriguez and Cortizas, 2014) showed that polysaccharides decrease exponentially with depth and the labile compounds are more degraded on surface, whereas more recalcitrant substrates are found at greater depth. Carbohydrates and carboxylic acids were the dominant drivers of nutrient bioavailability in fPMM, which also corroborates the chemical characterization of PMM done by Béasse et al (2015) and Quideau et al (2017), indicating the presence of labile short chain C substrates. Major drivers of nutrients in FFMM also shifted from mostly carbohydrates in the fresh to mostly amino acids in the stockpiled soils.…”

“…The current study also demonstrated the use of simple microbial functional profiles (CLPP) in assessing the effects of operational management practices on soil quality and the findings are comparable to other studies that used more sophisticated methods (e.g., Béasse et al, 2015; Quideau et al, 2017). Similar approach can be adopted for routine soil measurements and monitoring changes in the reclaimed and other disturbed sites.…”

“…For example, the severe disturbances associated with open-pit mining and subsequent reclamation activities have a significant effect on nearly all properties of soils. This has been reported in many studies related to physicochemical properties (Abdul-Kareem and McRae, 1984;Barbour et al, 2007), microbial community structure and functions (Stefani et al, 2018;Lewis et al, 2010, Béasse et al, 2015, and nutrient dynamics (Banning et al, 2011;MacKenzie and Quideau, 2012;Quideau et al, 2017).…”

Growth Response of Aspen and Alder to Fresh and Stockpiled Reclamation Soils

“…MacKenzie [16] found that stockpiling FFMM increased available phosphorus and potassium and did not substantially change total percent nitrogen or organic matter. In our study, the greater amount of phosphorus and potassium in stockpiled FFMM may partly be because the soil was obtained from a potentially more nutrient-rich site than the other soils, potential nutrient flush from decomposing or decomposed forest floor material [19], and the…”

“…Results from stockpiling peat and peat mineral mixes in Alberta also suggest that stored peat nutrient contents are similar to undisturbed peat, and changes in nutrient or organic carbon levels may be due to admixing with mineral soil [18]. Because the successful re-establishment of vegetation on FFMM and PMM is largely dependent on the nutrients these materials can provide [19], it is important to assess the nutrient status of stockpiled reclamation soils as this would provide a better indication of their suitability for forest-land reclamation than the duration of soil storage.…”