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Right-of-Way Science

It’s a hot, dry day in late June when my 12-year-old granddaughter Elanor and I, along with 25 other folks, visit the First Energy/Penelec Right-of-Way on SGL#33. Our friend, Dr. Carolyn Mahan, Professor of Biology and Environmental Studies at Penn State Altoona, has organized one of four scheduled bee-collection dates for this well-studied right-of-way.

A group of visitors exploring the powerline right-of-way on State Game Lands 33, June 2017

A group of visitors exploring the powerline right-of-way on State Game Lands 33, June 2017 (Photo by Therese Boyd of Penn State on Flickr, Creative Commons license)

Research on the best way to manage right-of-ways (ROW) has been ongoing at this site since 1953, which is, by far, the longest study of any ROW corridor in the world. A large 500 kV transmission line in Centre County, it passes up and over the Allegheny Front through a heavily forested area.

On this day, students and faculty from Ohio State University have joined representatives from First Energy, vegetation-management companies, and the Pennsylvania Game Commission along with Penn State faculty, staff, and students and collectors willing to help snag bees with bug nets and put them in killing jars so the insects can be identified, studied, and then stored in Penn State’s Frost Entomological Museum.

Back in the 1990s, Mahan first started working on this site as a graduate student with Dr. Richard Yahner when bird and mammal studies were underway. Yahner authored numerous papers on this site before his untimely death in 2015. When Mahan took over the work then, she put an emphasis on native pollinators, along with continuing studies of birds and plant species. Once a month in May, June, July and August volunteers collect bees in six different 50×25 meter sites for two hours both morning and afternoon.

Another powerline in PA that appears to be using wire-border zone management

Another powerline in PA that appears to be using wire-border zone management (Photo by Nicholas A. Tonelli in Wikimedia, Creative Commons license)

Before the collecting began, we heard about the various treatments used in an effort to determine which ones were most useful in keeping the electric lines operative in all kinds of weather, yet did not harm the mammals, birds, and insects that live on the ROW. Although management methods have varied since 1953, in the mid-1980s, they adopted the wire-border zone method in which the area directly under the transmission lines (wire) is managed for grasses, forbs, and low shrubs and the narrow border zone on each side of the wires for low-to-medium-sized shrubs.

The vegetative-management company uses one of six treatments, including (1) mowing and using a diluted herbicide on the wire zone, (2) a high volume foliar herbicide treatment, again in the wire zone, (3) an ultra-low volume treatment with herbicide only on target vegetation in the wire zone, (4)a low volume basal bark treatment where herbicides are sprayed on individual target plants to control trees and shrubs up to six inches in diameter in both the wire and border zones, (5)mowing in the wire and border area and (6) hand-cutting with a chainsaw.

A killing jar filled with various species of bees collected by Elanor Bonta

A killing jar filled with various species of bees collected by Elanor Bonta (Photo by Elanor Bonta)

The site where we were to collect bees has had the low volume basal bark treatment which has been the most successful in creating early successional habitat for native bees. In addition, the border zones have reacted well to this treatment and are important for birds, Research Assistant Brad Ross reported.

After more than an hour in the hot sun listening to various speakers, we were eager to get started collecting and watched as Dana Roberts, a Research Technologist in Penn State’s Department of Entomology, demonstrated how to carefully net a bee and put it in a jar with acetone. Elanor didn’t need any lesson. She is very proficient with an insect net, having learned from her father who has been collecting beetles since childhood.

Elanor with her collecting net

Elanor with her collecting net (Photo by Therese Boyd, Penn State, used with permission)

I, on the other hand, am not proficient with a net so I was in charge of holding and opening the killing jar whenever she netted a bee. During the collection period she caught several bees while I noted the wide variety of wildflowers in the wire zone—common milkweed, evening primrose, whorled loosestrife, goldenrod—and other native plants such as sweetfern, spreading dogbane, Virginia creeper, dewberry, and hay-scented fern. But most of the bees we collected were nectaring on the beds and beds of blooming non-native daisies brought from Europe centuries ago.

I was also interested in Ross’s research. He conducts bird singing surveys on eight sites four times a year during the breeding season. In addition, he and his helpers search for nests on the ROW. They had found 63 nests, 15 more than in 2016. For birds, he concluded, “It’s a source, not a sink.” He showed us an eastern towhee nest in a black cherry tree sapling on a border site that had been cut with a chainsaw but not treated with herbicide. Nearby, a blackberry shrub harbored a chestnut-sided warbler nest. I also heard singing field sparrows and an indigo bunting.

A common yellowthroat in Pennsylvania using a shrubby habitat (Photo by Dave Inman on Flickr, Creative Commons license)

A common yellowthroat in Pennsylvania using a shrubby habitat (Photo by Dave Inman on Flickr, Creative Commons license)

Since 1982, scientists have identified over 44 bird species on the ROW, most notably nesting common yellowthroats, American redstarts, field sparrows, indigo buntings, chestnut-sided warblers and eastern towhees, all species that use grassy, shrubby nesting areas, especially blackberry, mountain laurel, blueberry, witch hazel, hay-scented fern and poverty grass.

Other, earlier studies of reptiles and amphibians found that small snakes such as northern red-belly and northern ringneck snakes use the wire zone and salamanders the border zone.

A two-year study of small mammals comparing species numbers and richness with the nearby forest identified eight species—white-footed, woodland jumping and meadow jumping mice, meadow and red-backed voles, short-tailed and masked shrews and short-tailed weasels—on the ROW and only two species in the adjacent forest.

Still another study on deer use of the ROW in the early 1980s before and after herbicide treatment showed that deer actually increased after the treatment, using it 48% more than the forest as they browsed heavily on the resulting herbaceous vegetation.

An eastern tiger swallowtail butterfly on a thistle in Pennsylvania

An eastern tiger swallowtail butterfly on a thistle in Pennsylvania (Photo by Henry T. McLin on Flickr, Creative Commons license)

Even butterflies proved to be more abundant on the herbicide-treated sites than on hand-cut ones. They, like the bees, are valuable pollinators for the many wildflowers where they collect nectar. On that two-year study, scientists identified such natives as Aphrodite fritillaries, little wood satyrs, monarchs, spicebush and eastern tiger swallowtails.

Most abundant of all, though, were the numbers and diversity of bee species on our collection day and the others throughout the designated spring and summer months. In a draft of a paper authored by the five scientist conducting the work, including lead Postdoctoral Scholar Laura Russo from the Penn State Center for Pollinator Research as well as Mahan, Ross, H. Stout and D. Roberts, which is under review at the Journal of Pollinator Ecology, they wrote that they had “net-collected 1,056 bee specimens representing 96 bee species,” only five of which were not natives, and two which had never been identified in Pennsylvania. In addition, all six bee families in North America were represented.

Once again low and selective basal bark treatment yielded the largest number of bees and they concluded that furthermore, “These ROW have potential to provide valuable conservation land if managed to promote biodiversity.”

Marcia and Elanor on the right-of-way in SGL 33

Marcia and Elanor on the right-of-way in SGL 33 (Photo by Therese Boyd, Penn State, used with permission)

Elanor and I enjoyed the chance to work with scientists for a morning and to see how valuable the open land of a ROW can be in providing habitat for native species that need shrubby, grassy areas. But while there is the possibility of such management on the two to three million hectares of ROWS in the United States, I couldn’t help comparing what I saw on the SGL#33 ROW with the small ROW that goes up and over our lower ridge-and-valley mountain. When we first moved here in 1971, it had been sprayed from the air, killing everything on it.

Gradually the plants and trees returned, and we were able to persuade the power company to hand-cut the trees and treat the stumps with herbicide. On the Laurel Ridge side the ROW reverted to mountain laurel, lowbush blueberry, scrub oak and sweetfern and on the steep south side of Sapsucker Ridge to hay-scented fern and pale corydalis. In the First Field and flatter areas on either side of the field that were also part of the ROW, blackberry shrubs, goldenrod and asters grow. As far as we could see, no trees threatened the wire zone. Pointing out to the many college classes we have hosted here over the years how well our ROW was managed, especially the healthy scrub oaks, also called bear oaks, loaded with acorns for wildlife every year, has always been part of our managed-land tours.

A scrub oak in the powerline on Laurel Ridge with a cicada

A scrub oak in the powerline on Laurel Ridge with a cicada (Photo by Dave Bonta on Flickr)

But last fall we heard chainsaws on the Laurel Ridge side. To our horror, the electric line workers had cut down all the scrub oak, having been told by their boss to cut all hardwood species. Although scrub oak can grow up to 20 feet tall in the best of circumstances, ours have never grown much higher than the mountain laurel. That’s because they grew on inhospitable mountain soil and formed a dense and extensive thicket.

It seemed especially bittersweet to lose valuable shrubby habitat to ignorance after spending so much time on a model ROW. Unfortunately, this heavy-handed attitude to ROWS is more the rule than the exception.

 

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