Prospective impacts of oil spills on floodplain vegetation: Both crude oil and diluted bitumen increase foliar temperatures, senescence and abscission in three cottonwood (Populus) species

• Published in: PloS one Vol. 15; no. 3; p. e0230630
• Main Authors: Nielson, Kayleigh G, Woodman, Samuel G, Rood, Stewart B
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 27.03.2020; Public Library of Science (PLoS)
• Subjects: Abscission; Biology and Life Sciences; Bitumens; Bituminous materials; Carbon monoxide; Coatings; Comparative analysis; Crude oil; Diagnostic systems; Dilution; Earth Sciences; Engineering and Technology; Evaporative cooling; Experiments; Floats; Flood plains; Floodplains; Hydrocarbons; Leaves; Military electronics industry; Necrosis; Northern Hemisphere; Occlusion; Oil sands; Oil spills; Petrolatum; Petroleum industry; Petroleum pipelines; Physical Sciences; Physiology; Pipelines; Poplar; Populus angustifolia; Populus balsamifera; Rivers; Senescence; Species; Stomata; Studies; Surface temperature; Threatened species; Transpiration; Turgor; Vegetable oils; Vegetation; Wilting; Woodlands; Alberta; Canada; United States; Alberta Canada; United States > US; North America
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0230630

Oil pipelines are vulnerable at river crossings since floods can expose and rupture pipes, releasing oil that floats and coats floodplain vegetation. This study investigated the consequences of oil coatings on leaves of cottonwoods (riparian poplars), the predominant trees in floodplain woodlands around the Northern Hemisphere. The study compared conventional crude oil (CO) versus diluted bitumen (dilbit, DB), heavy oil originating from the Alberta oil sands; with petroleum jelly (PJ) as a reference. The treatments increased leaf surface temperatures (Tleaf) in narrowleaf and plains cottonwoods (Populus angustifolia, P. deltoides) and balsam poplars (P. balsamifera) (Control = 21.8°C, PJ = 23.7°C; CO = 26.2°C; DB = 28.1°C; Tair = 25°C). The leaf warming followed stomatal occlusion from the foliar coating, which would reduce transpiration and evaporative cooling, combined with increased solar warming with the darker oils. Tleaf varied across the three cottonwood species, with cooler, narrow, narrowleaf cottonwood leaves; intermediate plains cottonwood leaves; and warmer, darker, balsam poplar leaves (average Tleaf: narrowleaf = 23.8°C, plains = 24.3°C, and balsam = 26.7°C), with similar warming in each species following the different treatments. Across species and treatments, Tleaf was tightly correlated with foliar condition, which assessed turgor versus wilting of leaf blades and petioles, along with leaf necrosis and senescence (r2 = 0.980, narrowleaf; 0.998, plains; 0.852, balsam). This tight association indicates validity of both Tleaf and foliar condition as diagnostic measures. Crude oil and dilbit had similar foliar impacts, and for both, leaf abscission occurred within 2 to 3 weeks. Consequently, following an oil spill, remediation should commence quickly but extending vegetation removal beyond a few weeks would have limited benefit since the contaminated leaves would have abscised.