Forest vegetation responses to atmospheric depositions associated with oil sands mining operations Macdonald, S. Ellen1, Mark Fenn2, Mervyn Davies3 and Benoit Gendreau-Berthiaume1   1Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada 2United States Department of Agriculture, Forest Service, PSW Research Station, Riverside, California, USA 3Stantec Consulting Ltd., Calgary, AB, Canada

Vegetation assessment Jack pine dominated sites; Dry, poor soils, flat Thought to be sensitive to acid deposition Understory plant community Species richness – total and by vegetation type (mosses, lichens, forbs, graminoids, shrubs) Cover – total and by vegetation type Species composition (cover by species) Branch growth (canopy trees) Basal Area Increment of canopy trees (dendrochronological analysis of tree cores) pre-oil sands development (1957-1966) Recent (2000-2010)

Understory vegetation cover and richness (regressions): Positively related to several measures of N, S, Base cations, Potential Acid Input Negatively related to distance from center of oil sands mining Understory vegetation composition related to (constrained ordination): Potential Acid Input Base Cations Sulphur Nitrogen Macdonald, S. Ellen. 2015. Chapter 9. Responses of understory vegetation. pp. 134-144. In. Assessing forest health in the Alberta Oil Sands Region. T.A. Clair & K.E. Percy (editors). Wood Buffalo Environmental Association Report #2015-03-01. 209 pp.

P = 0.0395; R2 = 0.2264 P = 0.014; R2 = 0.304 Vascular Plant cover (%) Total Richness P = 0.0395; R2 = 0.2264 P = 0.014; R2 = 0.304

Forward selection of environmental variables in distance-based redundancy analysis

Center of oil sands mining Higher richness and cover Lower richness and cover

Branch growth (mean length of most recent branch internode for 10 trees per site) was inversely related to Potential Acid Input; not related to distance from centre of oil sands mining P = 0.024, R2 = 0.242 Macdonald, S. Ellen. 2015. Chapter 6. Plot vegetation description. pp. 85-94. In. Assessing forest health in the Alberta Oil Sands Region. T.A. Clair & K.E. Percy (editors). Wood Buffalo Environmental Association Report #2015-03-01. 209 pp.

Tree growth: possible to compare among sites for the time period before oil sands development and recent

BAI Pre-development (1957 – 1966): not related to (current) base cations, potential acid input or any other deposition variables Canopy trees: 54 – 68 years old at breast height in 2011

Not related to distance from centre of oil sands mining Recent (2000-2010) BAI positively related to base cations and negatively related to potential acid input Not related to distance from centre of oil sands mining Mixed effects model: P = 0.0079 Mixed effects model: P = 0.0084

Base cation inputs Center of oil sands mining JP 317 Trees growing faster; higher base cations Base cation inputs

Fertilization effect on understory vegetation? Understory plant cover and richness were greater in areas with higher N, S, base cation deposition and with higher Potential Acid Input Areas with richer/more abundant understory vegetation are generally closer to the oil sands development Understory composition also varied with N, S, base cation deposition Sites closer to oil sands mining had increased cover and richness of forbs and trailing shrubs Fertilization effect on understory vegetation? Recent tree growth is lower in areas with lower base cation inputs and higher Potential Acid Input This effect did not exist prior to oil sands development The areas with slower-growing trees are not necessarily closer to the oil sands development Tree growth was not related to N or S deposition variables

Moving forward: Analyze data from the edge sites Variation in space could be confounded with: topography, soils, parent material, microclimate, atmospheric CO2….. How have depositions changed over time – past and into the future? (changing technologies, new developments coming on-line)

Acknowledgements Wood Buffalo Environmental Association Kevin Percy, Tom Clair Navus Environmental (Kevin Renkema, Ashley Craig)