Sensitivity to Acidification of Forest Soils in Two Watersheds with Contrasting Hydrological Regimes in the Oil Sands Region of Alberta


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Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta. We evaluated the sensitivity of forest soils to acidification in two watersheds (Lake 287 and Lake 185) with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems. Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine (Pinus banksiana) or aspen (Populus tremuloides). Soils in the two watersheds were extremely to moderately acidic with pH (CaCl2) ranging from 2.83 to 4.91. Soil acid-base chemistry variables such as pH, base saturation, Al saturation, and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor > subsurface mineral soil > surface mineral soil. The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon. Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%, respectively; the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification. Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.

Original languageEnglish
Pages (from-to)747-757
Number of pages11
Issue number6
Publication statusPublished - 2007 Dec
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank Alberta Environment, Canada, for its support in the field work. Analysis of soil samples was partially supported by a grant from the Research Institute of Agricultural Science, Kangwon National University, Korea.

Funding Information:
∗1Project supported by the NOx-SO2 Management Working Group (NSMWG) under the Cumulative Environmental Management Association (CEMA), Canada (No. 2006-0003). ∗2Corresponding author. E-mail:


  • Al saturation
  • acid-buffering capacity
  • base saturation
  • pH
  • soil acidification

ASJC Scopus subject areas

  • Soil Science


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