COARSE WOODY DEBRIS EFFECTS ON BIOGEOCHEMISTRY IN TWO RECONSTRUCTED SOILS IN THE ATHABASCA OIL SANDS REGION IN ALBERTA, CANADA

• Author / Creator

  Kwak, Jin-Hyeob

• Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for land reclamation post open pit oil sands mining in northern Alberta, Canada. While in such land reclamation practices the organic matter comes from the peat material salvaged before land disturbance, coarse woody debris (CWD) can be used as an additional organic matter amendment for land reclamation. Effects of cover soil type (FMM vs PMM) and CWD (near vs away from CWD) on microbial community level physiological profile, extracellular enzyme activities, greenhouse gas emission rates and nitrogen (N) transformation rates were determined between 4 and 7 years after reclamation to assess whether applying CWD can facilitate land reclamation. Soil sampling and analyses were conducted and greenhouse gas emission rates were measured monthly during growing seasons within 5 cm from CWD and more than 100 cm away from CWD. Monthly in situ soil incubation was conducted and plant root simulators were incubated to assess net N transformation rates and N supply rates, respectively. A laboratory incubation experiment using 15N isotopic dilution was conducted to evaluate the effect of CWD leachate on gross and net N transformation rates. The soil microbial community level physiological profile was changed by CWD in FMM (p<0.01) but not in PMM. The CWD increased (p<0.05) metabolic microbial community function (averaged well color development during incubation of Biolog Ecoplates) by 10-30% in both cover soils. Microbial biomass (p<0.1) and enzyme activities (p<0.05) were 22-84 and 16-181%, respectively, greater in FMM than in PMM and CWD increased (p<0.1) microbial biomass by 2-58% in both cover soils but not enzyme activities. Soil respiration (p<0.05) and methane uptake (p<0.01) rates were greater in FMM than in PMM regardless of the distance from CWD. Coarse woody debris increased soil respiration (p<0.05) and methane uptake rates (p<0.1) by 22-33 and 13-34%, respectively, in FMM but not in PMM. Gross and net nitrification rates were 1.8 and 2.1 times, respectively, greater (p<0.01) in FMM than in PMM due to the greater microbial and enzyme activities in FMM. Net N mineralization rates were 2.1 times greater (p<0.01) in FMM than in PMM in laboratory and field incubation experiments due to the greater (p<0.01) N immobilization rates in PMM. The CWD increased (p<0.05) gross nitrification rates associated with increased microbial activities and function near CWD (field condition); however, addition of CWD extract also increased (p<0.05) N immobilization rates (laboratory incubation experiment) resulting in similar N transformation rates between near CWD and away from CWD. Nitrogen supply rates and inorganic N concentrations were not affected by both cover soil type and CWD due to the greater N uptake in FMM than in PMM and greater N immobilization near CWD than away from CWD. Applying CWD for land reclamation may increase N immobilization; however, it increases microbial activity and function thereby increasing organic matter decomposition. Effects of CWD on soil biogeochemistry differed depending on cover soil type and such effects were more significant in FMM than in PMM. Cover soils had contrasting properties and FMM is a better cover soil relative to PMM for oil sands reclamation with greater microbial biomass, microbial and enzyme activities and N transformation rates in FMM. Application of CWD enhanced microbial activities and function that would increase nutrient cycling and organic matter decomposition; therefore, CWD application should benefit early ecosystem development in upland reclamation.

• Subjects / Keywords

  • Oil sands reclamation
  • Athabasca oil sands region
  • Biogeochemistry
  • Coarse woody debris

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3542JM07

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.