Carbon and nitrogen mineralization in wetland soils of the Canadian Prairies
Dedzoe, Christian Dela
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Wetland soils form an integral part of the agricultural hummocky landscape in the Canadian Prairies. These soils sequester carbon and can serve as sources of greenhouse gases. Three distinctly different but contiguous soils – Humic Luvic Gleysols (HLG), Eluviated Dark Brown Chernozems (EDBC) and Calcareous Dark Brown Chernozems (CDBC) – located in the St. Denis National Wildlife Area (SDNWA) in four wetlands were selected for study with the aim of comparing the carbon (C) and nitrogen (N) mineralization parameters and determining soil-related factors that influence C and N mineralization in these soils. A short-term aerobic incubation study (16 d) was conducted to determine C mineralization. Nitrogen mineralization was examined using two soil N availability indices: nutrient supply rate (NSR) in a short-term incubation study (14 d) and aerobic leaching-incubation in a long-term study (16 wk). A first order model using non-linear least squares regression was fitted to cumulative C and N curves to determine C and N mineralization parameters (C mineralization potential, Co and C mineralization rate constant, kC; N mineralization potential, No and N mineralization rate constant, kN) for each soil type. Mean cumulative C mineralization, Co, mean cumulative N mineralization and No were highest in the surface horizons and decreased with depth in all the soils. The mean cumulative CO2 production values for the surface horizons were > 150 mg CO2-C kg–1 soil while the lower horizon values were < 80 mg CO2-C kg–1 soil. Surface mean cumulative N mineralization values were between 5 mg N kg–1 soil and 10 mg N kg–1 soil with the lower horizons being < 5 mg N kg–1 soil. The pattern was similar for Co and No in the surface horizons with values ranging from 200 mg CO2-C kg–1 soil to > 300 mg CO2-C kg–1 soil and from 8 mg N kg–1 soil to 28 mg N kg–1 soil, respectively. Nutrient supply rate also showed a similar pattern. The clay fraction showed a stronger negative correlation with the C mineralization parameters in the CDBC than in the other two soils. Organic C and N showed a highly significant positive correlation with almost all the mineralization parameters in all the soils. Overall, notwithstanding the differences in pedogenetic characteristics of the three soils, few significant differences were observed when their C and N mineralization assays were compared. The similarity in the biochemical characteristics of the soils suggests that the observed pedogenic differences do not reflect significantly in the C and N mineralization. Although the pedogenic differences are large, the effects of these differences on soil management are not agronomically significant and the soils can be managed together.
DegreeMaster of Science (M.Sc.)
CommitteeFarrell; Siciliano; Shirtliffe
Copyright DateSeptember 2010