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Power Lines and Problem Trees
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Power line rights-of-way (ROWs) are necessary to deliver safe and reliable power to northern communities and industries. Tall trees can cause damage to power lines, power outages, wildfires from contact with active lines, and can hinder accessibility during maintenance. Maintaining compatible vegetation on ROWs is mandatory and can be a challenging task. In boreal Saskatchewan, vegetation has typically been managed through mechanical clearing, which can promote suckering and heavy reseeding of hazardous vegetation, creating a greater problem in following years [1,2,3]. [Top of Page]
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Examples of compatible/desirable vegetation vs incompatible/
hazardous vegetation on a right-of-way.
Integrated Vegetation Management
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Integrated vegetation management (IVM) has the potential to increase the efficiency and lower the cost of ROW maintenance, as well as, reduce associated environmental impacts. IVM is the practice of promoting desirable, stable, low-growing plant communities that will resist invasion by tall-growing tree species; through the use of appropriate, environmentally sound, and cost-effective control methods. These methods can include a combination of mechanical (brushing, mowing, hand cutting), chemical (herbicides), and biological (planting, seeding) treatments [4].
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Establishment of low-growing plant communities have been proven to reduce tree growth and establishment on ROWs in areas such as Quebec [5], Ontario [6], New York State [7] and Pennsylvania State [8]. IVM can be designed to meet other ecological and socioeconomic objectives, such as creation of wildlife [9] and pollinator [10] habitat, recreational use [10], and preservation of regional livelihoods, culture and traditions[10,11].
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Developing stable, low growing plant communities can take years. Since IVM is a decades long process, treatment options must be considered for long term and short term cost-benefits. No single treatment will fit each situation, so treatments must be evaluated and adjusted on a case by case basis. With multiple tools and techniques to use, vegetation managers can adjust to the ever-changing environment and create specialized plans. [Top of Page]
Plant Competition and Right-of-Way Vegetation Management
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All plants must compete for resources in their environment to grow and reproduce. Competition for light occurs aboveground and plants with dense foliage or canopies may suppress other plants by creating shade. Competition for water and nutrients occur belowground where root networks and nutrient storage may determine the success of the plant. To out compete other species certain plants may even release toxic chemicals into their surroundings (allelopathy) in an attempt to gain a competitive advantage. The Crowberry shrub (Empetrum nigrum spp. Hermaphroditum) is known to chemically inhibit the growth of Scots Pine (Pinus silvestris) and Aspen (Populus tremula) seedlings in boreal Sweden [12].
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Grasses and low growing, dense shrub communities are known to outcompete trees, reducing their regrowth or establishment and can create stable communities needing little maintenance [8,11,12,13,14,15]. Bluejoint Reedgrass (Calamagrostis canadensis) roots and litter can create a dense mat that physically prevents Aspen (Populus tremuloides) sucker and seedling penetration. This mat also creates shade which maintains cooler soil temperatures, further preventing seedling and sucker development [11,13,14]. Aggressively growing Orchardgrass (Dactylis glomerata) can outcompete tree species on ROWs if seeded immediately after mowing [6]. Coppicing, or cutting the stems of compatible shrubs to promote their suckering, has been used effectively on ROWs in New York State [16]. Transplanting of woody shrubs has been effective on Quebec ROWs [17]. Understanding how plants compete on ROWs can help to identify management strategies that use natural processes to prevent tall tree establishment and growth. [Top of Page]
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Techniques Used in Integrative Vegetation Management
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No single vegetation treatment will work on every ROW. Having a range of vegetation management tools is critical for effective IVM [10]. Prior to the 1940s, mechanical methods such as brushing, mowing or hand cutting were the only tools readily available, but today there are multiple techniques that can be used in combination for improved results [11].
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Mechanical methods are still widely used across North America [18] and are highly effective for controlling some species. However, mechanical methods can increase the growth and spread of plants that sucker [19,20] such as Trembling Aspen (Populus tremuloides), Balsam Poplar (Populus balsamifera) [2,3] and Birch (Betula papyrifera). By physically removing the aboveground plant tissue growth from stump or root suckers can eventually lead to these incompatible/hazardous species becoming dominant on the ROW [3,20]. In addition, mechanical methods often involve the use of heavy machinery which can create varying amounts of soil disturbance (ex: compaction, erosion) [11] and noise which may frighten nearby wildlife.
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Sucker regrowth from the roots and stem.
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Since World War II, chemical herbicides have become widely used [18]. Herbicides, when used correctly, are a potential tool for boreal ROW vegetation management. Many products have been created and approved (registered) for use on hazardous ROW species, such as Trembling Aspen, Balsam Poplar [2,3] and Willows [21,22], which are known for aggressive suckering after aboveground clearing. Herbicide applications are intended to kill both the aboveground and belowground (root) portions of plants. Killing the roots prevents suckering [23]. Studies have shown that selective herbicide usage is the most effective method of achieving compatible, resistant, stable species cover [11,19,24,25,26,27]. In addition, as the desired plant communities become established less and less intervention is needed [10]. Public and local community concerns regarding the impact of herbicide use on ROWs is an on-going issue in many areas of Canada and needs to be addressed as part of an IVM plan.
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Ecological or biological manipulation of vegetation is a method that involves exploiting natural plant competition. Using competitive plant interactions can limit the need for other forms of maintenance and so reduce disturbance to the natural environment [10,11]. The use of ecological manipulation on boreal ROWs is not widespread and successful use of this technique requires further investigation. [Top of Page]
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References
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[1] Nickerson, NH. 1992. Impacts of Vegetation Management Techniques on Wetlands in Utility Rights-of-way in Massachusetts. Journal of Arboriculture, 18(2): 102-107.
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[2] Frey BR, Lieffers VJ, Munson AD, Blenis PV. 2003. The Influence of Partial Harvesting and Forest Floor Disturbance on Nutrient Availability and Understory Vegetation in Boreal Mixedwoods. Canadian Journal of Forest Research, 33:1180-1188.
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[3] Ilisson T, Chen HYH. 2009. Response of Six Boreal Tree Species to Stand Replacing Fire and Clearcutting. Ecosystems, 12: 820-829.
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[4] United States Environmental Protection Agency. December, 2016. Pesticide Environmental Stewardship Program (PESP). Benefits of Integrated Vegetation Management (IVM) on Rights-of-way. https://www.epa.gov/pesp/benefits-integrated-vegetation-management-ivm-rights-way Accessed January 23, 2017.
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[5] Meilleur A, Veronneau H, Bouchard A. 1997. Shrub Propagation Techniques for Biological Control of Invading Tree Species. Environmental Management, 21: 433-442
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[6] Brown D. 1995. The Impact of Species Introduced to Control Tree Invasion on the Vegetation of an Electrical Utility Right-of-way. Canadian Journal of Botany, 73:1217-1228.
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[7] McLoughlin KT. 2014. Integrated Vegetation Management: From its Roots in IPM to the Present. pp 227-270. In G. J. Doucet (Ed.). 10th International Symposium: Environmental Concerns in Rights-of-Way Management. Utility Arborist Association, Champaign, IL.
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[8] Bramble WC, Byrnes WR. 1983. Thirty Years of Research on Development of Plant Cover on an Electric Transmission Right-of-way. Journal of Arboriculture, 9:67-74.
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[9] Clarke DJ, Pearce KA, White JG. 2006. Powerline Corridors: Degraded Ecosystems or Wildlife Havens? Wildlife Research, 33:615-626.
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[10] Nowak CA, Ballard BD. 2005. A Framework for Applying Integrated Vegetation Management on Rights-of-way. Journal of Arboriculture, 31:28-37.
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[11] Isbister, K. 2016. Early Responses of Northern Boreal Vegetation to Power Line Right-of-way Management Techniques Including the Acute Toxicity of Imazapyr and Triclopyr to Non-target Plants. Masters thesis. Department of Plant Sciences, University of Saskatchewan.
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[12] Zackrisson O, Nilsson M. 1992. Allelopathic Effects by Empetrum hermaphroditum on Seed Germination of Two Boreal Tree Species. Canadian Journal of Forest Research, 22:1310-1319.
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[13] Landhäusser SM, Lieffers VJ. 1998. Growth of Populus tremuloides in association with Calamagrostis canadensis. Canadian Journal of Forest Research, 28:396-401.
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[14] Landhäusser SM, Mulak TL, Lieffers VJ. 2007. The Effect of Roots and Litter of Calamagrostis canadensis on Root Sucker Regeneration of Populus tremuloides. Forestry, 80:481-488.
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[15] Niering WA, Goodwin RH. 1974. Creation of Relatively Stable Shrublands with Herbicides: Arresting "Succession" on Rights-of-way and Pastureland. Ecology, 55:784-795.
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[16] Ballard BD. 2006. Managing Shrubs on Powerline Corridors in Central New York: Findings From the Environmental Complex. Syracuse, New York: State University of New York, p. 184.
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[17] Meilleur A, Veronneau H, Bouchard A. 1997. Shrub Propagation Techniques for Biological Control of Invading Tree Species. Environmental Management, 21:433-442.
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[18] Sulak JA, Kielbaso JJ. 2000. Vegetation Management Along Utility Transmission Lines in the United States and Canada. Journal of Arboriculture, 26:198-205.
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[19] Yahner RH, Hutnik RJ. 2004. Integrated Vegetation Management on an Electric Transmission Right-of-way in Pennsylvania, Journal of Arboriculture, 30:295-300.
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[20] Luken JO, Hinton AC, Baker DG. 1991. Assessment of Frequent Cutting as a Plant-community Management Technique in Power-line Corridors. Environmental Management, 15:381-388.
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[21] Amiro BD, Courtin GM. 1981. Patterns of Vegetation in the Vicinity on an Industrially Disturbed Ecosystem, Sudbury, Ontario. Canadian Journal of Botany, 59:1623-1639.
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[22] Carleton TJ, MacLellan P. 1994. Woody Vegetation Responses to Fire Versus Clear-cutting Logging: A Comparative Survey in the Central Canadian Boreal forest. Ecoscience, 1:141-152.
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[23] Egler F. 1954. Vegetation Science Concepts I. Initial Floristic Composition, a Factor in Old-field Vegetation Development. Vegetatio 4:412-417.
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[24] Bramble WC, Byrnes WR, Hutnik RJ, Liscinsky SA. 1991. Prediction of Cover Type on Rights-of-way After Maintenance Treatments. Journal of Arboriculture, 17:38-43.
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[25] Dreyer G, Niering W. 1986. Evaluation of Two Herbicide Techniques on Electric Transmission Rights-of-way: Development of Relatively Stable Shrublands. Environmental Management, 10:113-118.
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[26] Niering WA, Dreyer GD, Egler FE, Anderson JP, Jr. 1986. Stability of Viburnum lentago Shrub Community After 30 Years. Bulletin of the Torrey Botanical Club, 113:23-27.
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[27] Mercier C, Brison J, Bouchard A. 2001. Demographic Analysis of Tree Colonization in a 20-year-old Right-of-way. Environmental Management, 28:777-787.
Last Updated: January 2017
