Hydrocarbon Tolerance Correlates with Seed Mass and Relative Growth Rate

ABSTRACT

The abundance and vegetation cover of plant species with different seed masses growing on crude oil contaminated and uncontaminated field plots were examined. In addition, seedling mass and relative growth rate of eight plants in four seed mass classes were compared in contaminated and uncontaminated soils. Species producing seed in the second largest seed class (1.0 to 9.9 mg) were more common on contaminated than uncontaminated field plots. Species with seed in the smallest seed class (< 0.1 mg) were less common on contaminated than uncontaminated plots. Species with seed masses between 1.0 and 9.9 mg formed 15% more vegetation cover, and those with masses between 0.1 and 0.9 mg formed nearly 15% less vegetation cover on contaminated compared to uncontaminated field plots. In the growth chamber, species with larger seeds produced approximately 25% less seedling mass and exhibited a 32% reduction in relative growth rate, when grown in contaminated compared to uncontaminated soil. Small-seeded species had reductions of 95% in seedling mass and 72% in relative growth rate. Species with the highest relative growth rates in uncontaminated soil had the lowest seedling mass in contaminated soil. Seed mass and relative growth rate were negatively correlated (r = 0.866).

Keywords:

• crude oil
• hydrocarbon tolerance
• phytoremediation
• plant screening
• seedling mass

ACKNOWLEDGMENTS

Funding for this research was provided by the Canadian Association of Petroleum Producers, Program of Energy Research and Development, Environment Canada and the National Sciences and Engineering Research of Canada.

Notes

^a,b Based on Acton et al., 1998.

^c C = Clay; L = Loam; S = Sand; Si = Silt.

^d Indicates if native prairie surrounded, was adjacent to, or within 1.6 km of the contaminated plot.

^e Elapsed time since initial contamination.

^f AP = Aspen Parkland.

^g MG = Mixed Grassland.

^h Unlined soil pits used to store and/or burn produced fluids such as liquid hydrocarbons, process chemicals, crude bitumen or salt water, and filled with soil.

^a TPH represents Total Petroleum Hydrocarbons.

^a Amended with one part potting soil to three parts contaminated soil.

^a Values represent mean ± SE.

^b Native species grew naturally in western Canada prior to European colonization; nonnative species arrived after European colonization.

^a TPH = Total Petroleum Hydrocarbons.

^b U = Uncontaminated plot.

^c C = Contaminated plot.

^d Significantly lower at P ≤ 0.05 using Student's t-test.

^a,b Cover and frequency data are based on 20 observations per plot at 14 sites.

^c U = Uncontaminated.

^c+Designates exotic species.

^d C = Contaminated.

^f *Significantly lower at P ≤ 0.05 using Student's t-test.