The impact of atmospheric acid deposition on tree growth and forest understory vegetation in the Athabasca Oil Sands Region

Sci Total Environ. 2019 Dec 15:696:133877. doi: 10.1016/j.scitotenv.2019.133877. Epub 2019 Aug 13.

Abstract

Atmospheric acid deposition is of major concern in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada, which is home to the third largest oil reserve in the world. After decades of oil sands production in the AOSR, the potential impact of deposition on forest health, including tree growth and understory biodiversity, is still not clear. We evaluated the relationship of modelled/interpolate atmospheric deposition of nitrogen (N), sulphur (S), base cations (BC), and derived potential acid input (PAI) from surface oil sands mining with: (1) the radial growth (i.e. basal area increment; BAI) of jack pine (Pinus banksiana Lamb.) trees using data from two decadal time periods, prior to (1957-1966) and during (2001-2010) active oil sands development in the AOSR; and (2) forest understory vegetation (abundance, diversity, and composition), which is an important component of forest biodiversity. BAI of jack pine trees varied with N, S, and BC deposition between the two time periods, and with the direction of the site relative to main emission sources. Growth was higher in areas close to the oil sands surface mining operations prior to and after oil sands development. BAI was also positively related to atmospheric deposition in the recent period, but these relationships were weaker in the active period versus the non-active period. Understory vegetation - including vascular plant cover, richness, and diversity - increased in relation to modelled atmospheric N and S deposition. There was limited correlation between soil pH or the BC:Al ratio (indicators of soil acidification) and BAI and understory vegetation responses. No evidence was found for detrimental effects of atmospheric emissions (and subsequent deposition) from oil sands production on tree growth or forest understory vegetation. The results, if anything, suggest a fertilization effect due to enhanced atmospheric deposition of nitrogen compounds.

Keywords: Basal area increment; Jack pine; Nitrogen deposition; Nitrogen fertilization; Oil sands development; Soil-mediated acidification; Sulphur deposition; Understory vegetation.

MeSH terms

  • Acid Rain / analysis*
  • Air Pollutants / analysis*
  • Alberta
  • Atmosphere
  • Environmental Monitoring*
  • Forests*
  • Oil and Gas Fields*
  • Trees / growth & development*

Substances

  • Acid Rain
  • Air Pollutants