Canadian Forest Service Publications
Sulfur impacts on forest health in west-central Alberta. 1994. Maynard, D.G.; Stadt, J.J.; Mallett, K.I.; Volney, W.J.A. Natural Resources Canada, Canadian Forest Service, Northwest Region, Northern Forestry Centre, Edmonton, Alberta. Information Report NOR-X-334.
Issued by: Northern Forestry Centre
Catalog ID: 11938
The processing of sour natural gas results in the emission of sulfur dioxide (SO2) and elemental sulfur (S0). An assessment was carried out in 1991 to compare soil and foliar chemical properties originally measured in 1981 and 1985 in forests near two sour gas processing plants in west-central Alberta. This study was expanded to evaluate forest health and tree growth in relation to sulfur (S) deposition in mature and immature lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and mature trembling aspen (Populus tremuloides Michx.). Ten (50 × 2 m) plots were established in 30 mature lodgepole pine sites, in 6 young lodgepole pine sites, and in 3 trembling aspen-dominated sites. The mature pine sites were classified into 3 deposition classes: high, medium, and low. The distribution of measurable S0 deposition increased from 2 km to 4–6 km from the S0 load-out areas; however, S0 concentration in the LFH near the gas plants has decreased since 1981. The medium deposition class sites had S concentrations in the LFH and foliage 6–20% higher than the low deposition class sites. Calcium (Ca) and magnesium (Mg) concentrations and pH were about 10% less in the medium deposition class sites than in the low deposition class sites. It was, however, not possible to determine a cause and effect relationship between higher S in these sites and lower pH, Ca and Mg. A greater proportion of recently dead trees was found in high deposition class sites, but no difference was seen between the other two deposition classes. There was no increase in insect- and disease-caused damage with increased S deposition in the pine stands. Trembling aspen appeared to be affected by S0 deposition with increased proportions of dead and declining trees and increased incidences of Armillaria root rot and Hypoxylon canker in S0-dusted areas. There were no differences among deposition classes on radial increments at dbh. Annual volume increments were depressed in high S0 deposition sites; however, specific volume increment was depressed in both the medium and high deposition classes indicating a possible physiological impact historically. Elevated S concentrations in the LFH and foliage and a depression in the annual volume increments were the only indicators of S impacts in lodgepole pine forests near the two sour gas processing plants. There was no apparent widespread forest decline outside of areas dusted with S0.