Mowing plots on State Game Lands 33 featured a lower abundance and taxa richness of bees than most plots treated with herbicide applications.
Mowing plots on State Game Lands 33 featured a lower abundance and taxa richness of bees than most plots treated with herbicide applications.
Mowing plots on State Game Lands 33 featured a lower abundance and taxa richness of bees than most plots treated with herbicide applications.
Mowing plots on State Game Lands 33 featured a lower abundance and taxa richness of bees than most plots treated with herbicide applications.
Mowing plots on State Game Lands 33 featured a lower abundance and taxa richness of bees than most plots treated with herbicide applications.

Environmental Research for ROW Management

July 8, 2022
The updates from a long-term vegetation management study indicate best practices for managing ROW habitats.

The State Game Lands 33 (SGL 33) research project is the longest continuous study of vegetation management practices and their environmental impact throughout utility rights of way (ROWs). New findings from this research provide further insight regarding best practices for supporting electrical transmission reliability and the development of early successional habitat for floral and faunal species.

Countless forms of incompatible vegetation present a variety of issues for utility companies across the country. While trees pose a constant threat to fall or grow into overhead transmission lines, undesirable plant communities composed of tall-growing woody plant species often overtake land below wires and conductors as well as 10 ft beyond their outer edge. The ongoing presence of incompatible vegetation in this area, known as the wire zone, can compromise electrical transmission reliability, worksite safety and ROW accessibility. However, the environmental impact of incompatible vegetation may be the most noteworthy.

Several vegetation management strategies can be used to impede the development of incompatible plant species that threaten the integrity of utility infrastructure. However, certain methods also support the development of early successional habitat in the border zone, which includes all land within 10 ft of a ROW. Supporting the development of low-growing trees and shrubs in this area creates habitat that is not only compatible with native wildlife species, but also with electrical transmission lines.

The SGL 33 research project in central Pennsylvania has analyzed the environmental effects of various vegetation management strategies for decades. Since 1953, SGL 33 researchers have examined the impact of numerous vegetation control methods throughout utility ROW corridors and tracked the effects each strategy has on natural resources, including plant communities and various wildlife groups. Nearly 70 years later, contributors to the longest continuous study of its kind continue to share the latest findings from this research and communicate best practices learned for environmental sustainability as well as electrical transmission reliability.

Making Research a Resource

With the help of funding partners, including Corteva Agriscience, FirstEnergy Corp., PECO Energy Company, Asplundh Tree Expert Company and TREE Fund, researchers from Pennsylvania State University (PSU) examine the ecological impacts of various treatment methods on field plots throughout SGL 33. Similar studies also have been conducted on State Game Lands 103 (SGL 103) in Centre County, Pennsylvania, as well as the Green Lane Research and Demonstration Area (GLR&D) in Montgomery County, Pennsylvania, which has served as an SGL 33 companion site since 1987.

FirstEnergy helped establish SGL 33 plots by applying a variety of legacy control methods at the onset of the environmental studies. These methods included:

  • Mowing
  • Hand-cutting
  • Foliar herbicide application
  • Combination of mowing and herbicide application
  • Low-volume basal bark application

Most recently, FirstEnergy applied additional treatments to these plots in 2016 to test myriad Integrated Vegetation Management (IVM) practices and enable SGL 33 researchers to assess their environmental impact in the years that followed. For FirstEnergy, this ongoing research provides more credibility for the tools and practices used by the utility to maintain the reliability of its extensive transmission system.

Over the years, results from these sites have shown that mechanical mowing, hand-cutting and other mechanized or non-selective control methods can encourage the development of incompatible plant communities when used exclusively. However, vegetation managers can complement mowing results by employing a strategy associated with IVM principles.

Why IVM?

IVM-based programs use a variety of control methods, including chemical, biological and mechanical techniques, to control incompatible vegetation. Because plant communities change quickly due to natural plant succession, IVM practices are structured to accomplish two particular goals within utility ROW: control incompatible stem densities and develop tree-resistant cover types that prevent the development of targeted trees. Doing so not only protects electrical transmission lines from encroaching vegetation, but also can create early successional habitat that supports diverse wildlife and pollinator communities.

“We need to have diversity to ensure we have resilience built into our natural ecosystems,” says Carolyn Mahan, professor of biology and environmental studies at PSU and principal investigator for SGL 33. “We’re currently seeing wildlife species being threatened by habitat loss, infectious pathogens and competition from non-native species. What we need to see more than ever in our wildlife communities is resilience. And we get that resilience through biodiversity.”

Studying the effects of different vegetation management practices and the support they provide to a variety of life throughout utility ROW corridors has enabled SGL 33 researchers to support the development of biodiverse habitat for decades. While the project’s contributors understand the impact of using various strategies, sharing this information with energy companies and their contract partners is an essential approach to reshaping the industry’s standards for vegetation management.

Latest Findings

Earlier this year, SGL 33 researchers developed a report that shares results from the project’s latest three-year research cycle, which details the effects vegetation management strategies had on floral and faunal species throughout SGL 33 sites from 2018 to 2021. This research compared the results of different vegetation management strategies to identify which methods were most effective at developing herbaceous-dominated communities within the wire zone as well as shrubs and low-growing tree saplings in the border zone.

Each strategy tested was managed to include a 95-ft wire zone and 30-ft border zone on each side of transmission line corridors. The size of each plot was about 3 acres at SGL 33 and 2.5 acres at GLR&D. These sites provided ideal landscapes for the assessment of each method of control and its effects on various plant, animal and insect species. Results addressed management practices and their apparent impact on vegetation, breeding birds, pollinators and ground beetles; and generally favored the use of selective herbicide applications for biodiversity management over mechanical treatments or nonselective herbicide applications.

Establishing Tree-Resistant Cover Types

To test the impact of vegetation management strategies on incompatible stem densities, a total of five control methods were applied to SGL 33 plots in 2016. In addition to hand-cutting and mowing, a total of three herbicide treatments were tested:

  • High-volume foliar (nonselective)
  • Low-volume foliar (selective)
  • Low-volume basal bark

When results were measured in July 2019, data showed that plots treated in the wire zone and border zone using low-volume foliar (LVF) and high-volume foliar (HVF) herbicide applications generally featured incompatible stem densities lower than those treated with mechanical strategies (see the graph on page 6). Comparatively, plots treated with low-volume basal (LVB) applications yielded zero incompatible trees, and hand-cutting treatments had the tallest (20-plus ft) and the highest density of incompatible trees for treated plots within the wire zone.

“What is good for wildlife on a right-of-way depends on the wildlife,” Mahan says. “However, selective herbicide applications are best at achieving two objectives: keeping compatible trees clear of power lines and simultaneously providing habitat for native wildlife. We’ve found that any selective herbicide treatment featuring backpack sprayer applications works best to achieve both.”

Impact on Breeding Birds

Evolving land-use practices and the suppression of natural disturbances that create early successional habitat for native bird communities have caused a steep decline in breeding bird populations throughout the United States in recent years. That’s why SGL 33 research has focused on enhancing the benefits of the wire zone-border zone method of IVM, which has benefited early successional birds since IVM practices were first tested in the early 1980s.

In terms of species richness, the abundance of breeding birds was consistently lower on sites treated with hand-cutting and mowing strategies over the past three years (see the graph on page 7). Conversely, a higher abundance and richness of breeding birds were noted in areas where selective herbicide treatments were used as part of an IVM-based approach for both wire zone and border zone management. In fact, LVF and LVB application sites with accompanying border zones contained a higher abundance and richness of breeding birds when compared with mechanically treated sites or sites with no border zone at all.

SGL 33 and SGL 103 sites managed with herbicides were either comparable or more beneficial to breeding bird communities in terms of productivity and nesting success than areas to which mechanical treatments were applied. The importance of border zone establishment should not be understated, as SGL 33 research shows that these areas are largely responsible for the retention of large and diverse bird populations throughout utility ROW. In fact, SGL 33 results indicate that the presence of border zones — even narrow border zones — along the wire zone is the most important predictor of diverse breeding bird communities.

Diversifying Pollinator Habitats

Similar to breeding bird populations in the United States, pollinator populations have been declining for several years, and habitat loss has been noted as a contributing factor. According to the National Resources Conservation Service, about 75% of the world’s flowering plants and about 35% of the world’s food crops depend on animal pollinators to reproduce. As utility ROW corridors represent an ideal landscape for pollinator habitat to exist, SGL 33 research goals in 2019 included the collection of flower-visiting insects.

Researchers surveyed plots treated with five different vegetation management strategies to assess and compare bee diversity, abundance and taxa richness. Strategies tested in this research included mowing and hand-cutting practices, as well as three different herbicide applications: HVF, LVF and LVB. Noteworthy differences in these sampling efforts include:

  • Mow plots were added in July 2019.
  • Fewer flowering plants were present on the hand-cut plot.
  • Terrain for the hand-cut plot was unequal to other plots.

In general, mowing plots featured a lower abundance and taxa richness of bees than most herbicide-treated plots. These results suggest IVM with herbicides is a compatible approach to supporting native bee populations and diversity along ROW corridors. Whereas the fewest number of bees, specimens and taxa were collected on sites where hand-cutting strategies were applied, the most bees and taxa were collected on sites treated with herbicides, with LVF sites producing the most specimens (see the graph on page 8). It’s also worth noting that LVB applications yielded a consistently high abundance and taxa richness of native bees across all three years following treatment.

Early Ground Beetle Insights

Using pitfall traps, SGL 33 researchers began comparing the abundance, taxa richness and diversity of ground and rove beetles on ROW plots in 2019. Given their relative abundance and sensitivity to environmental changes, ground beetles are excellent bioindicators, which is why SGL 33 research can be used to enhance understanding of the environmental impact IVM practices have within utility ROW. Treated with the same five vegetation management strategies used for pollinator research, these plots are used to assess the populations and diversity of ground beetles.

A total of 7,847 specimens were collected at SGL 33 in 2020, with the most collected from hand-cutting sites in late summer. Comparatively, the most non-beetle invertebrates were collected from sites treated with a combination of mowing and herbicide applications across all months.

“The ground beetle data are intriguing and require further study,” Mahan says. “When we look at these data, we find that all treated plots featured beetle specimens that could indicate a healthy ecosystem. The hand-cutting method has yielded a higher abundance of ground beetles overall and in the latter portion of the summer. However, abundance doesn’t tell you the whole story. The species-level data that we are still in the process of analyzing can provide a clearer picture of ground beetle response to different treatments.”

Additional environmental research will help SGL 33 researchers understand why plots treated with herbicides support relatively more beetles in early summer, and why mechanically treated plots support more beetles late in the summer. Early signs point to the type of plant communities each strategy promotes.

“We think that ground beetles are responding to the cover type, which consists of a very thick woody vegetation where mechanized hand-cutting is performed,” Mahan says. “This creates a micro-environment that is cooler and leafier. Ground beetles are likely responding to the habitat structure that hand-cutting creates. Once we understand the species differences among each plot, and not just abundance, we’ll have a better understanding.”

Mahan expects all ground beetle data to be summarized and published in 2022, which will align with the launch of a new study concerning Lepidoptera, an order of insects composed of butterflies and moths. As SGL 33 research continues to provide educational insights for energy companies and their vegetation management partners regarding the positive impact IVM practices can have on ecosystems within utility ROW, Mahan emphasizes the importance of application-based education as well.

“Herbicides can and should be used properly,” Mahan says. “IVM works really well in theory, but we don’t have enough experts using it. There’s definitely a need for well-trained professionals to ensure IVM applications are completed properly. Entities throughout the industry should want that.”

Enhancing Education

Corteva, a funding partner of SGL 33 research, shares the same sentiment as Mahan. That’s why Corteva recently launched Vegetation Education, an online resource designed to help vegetation managers stay up to date on everything from industry-leading management strategies and techniques to best practices for herbicide use, tank-mixing guidance and more. Filled with self-guided trainings, industry success stories and a management portfolio guide, Vegetation Education provides theinsights
industry practitioners need to ensure success in the field.

Energy company stakeholders also had the opportunity to learn about best practices in vegetation management and the evolution of environmental stewardship at the 2022 ROW Sustainability Summit in State College, Pennsylvania. Presented by Corteva, FirstEnergy, PSU, the Utility Arborist Association, the University of Illinois-Chicago and the Rights-of-Way as Habitat Working Group, the summit consisted of research presentations, working sessions and tours of SGL 33 research sites.

Now equipped with three more years of environmental results, those involved with SGL 33 research have the insights needed to establish industry best practices as new standards for utility vegetation management. As sustainability, environmental and vegetation management professionals continue to familiarize themselves with the long-term research findings and strategic communications tools at their disposal, the question is no longer why they should adapt IVM practices, but instead, how and when.

Editor’s Note: Utility vegetation management professionals can learn more about SGL 33 and ROW ecological research conducted by PSU by visiting

Shawn Standish ([email protected]) is a manager of vegetation program management with FirstEnergy Corp. With more than two years of industry experience, he oversees vegetation management operations for FirstEnergy to ensure the safety, reliability and regulatory compliance of its electric system. Shawn is also a leading cooperator with the State Game Lands 33 research project. He is based in Mechanicsburg, Pennsylvania.

Travis W. Rogers ([email protected]) is a market development specialist for Corteva Agriscience within the Eastern U.S. Pasture & Land Management district. In his role, he supports 10 territory managers, serves as the interface between the commercial sales and R&D units, and works on a variety of product and market development projects. He has 15 years of experience working with energy companies, federal and state agencies, conservation groups, channel partners and service contractors within the rights-of-way and forestry industries. He is based in Charleston, South Carolina.

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