Long term effects of electrical right-of-way vegetation management on floral and faunal communities (2021-2024)

March 19, 2025March 19, 2026 Barb 8 Views

2021-2024, Carolyn G. Mahan, PhD, Pennsylvania State University

Goals of the three-year project

Implement a ground beetle protocol at GLR&D site. Identify and summarize findings of ground beetle surveys in cooperation with the Center for Pollinator Research and the Frost Entomological Museum. Species of conservation concern will be highlighted and implications
for ecosystem services will be discussed.
Conduct breeding season singing surveys for birds at the SGL 33 and SGL 103 sites. Data will be used to determine which early successional species are using the right-of-way for nesting habitat. Singing surveys at SGL 103 will be supplemented with bird productivity (nesting success) research. This bird productivity data at SGL 103 will provide a needed second year of data mid-way through a vegetation treatment cycle at that study site.
Conduct timed-area count survey for snakes at GLR&D site. Substrate and habitat use will be noted and implications for ROW management addressed based upon species of snakes detected.
Develop Lepidopteran protocol in conjunction with the Frost Museum and Center for Pollinator Research at The Pennsylvania State University. This protocol will address capture and identification techniques, voucher collection, and standardization of effort across our study sites.
Conduct vegetation surveys at all locations to document vegetation community and species richness.
Conduct breeding season singing surveys for birds at the SGL 33 and SGL 103 sites
Lepidopteran sampling protocol will be tested at all sites to finalize sampling effort needed to capture species richness and diversity at the ROW
Implement the Lepidopteran sampling protocol (e.g., conduct the Lepidopteran surveys) at all three study areas (SGL 33, GLR&D, SGL 103)

Goal: Implement a ground beetle protocol at GLR&D area (delayed due to COVID pandemic). Identify and summarize findings of ground beetle surveys in cooperation with the Center for Pollinator Research and the Frost Entomological Museum. Species of conservation concern will be highlighted and implications for ecosystem services will be discussed.

Completed as follows: From 1 June to 29 July 2021 we used pitfall traps to perform two 72-hr-duration ground beetle collections at five plots at GLR&D. Overall, 51 individual ground beetles representing 14 species were collected—the hand cut plot had the greatest number of individuals, the foliar application had the greatest taxa richness, and the foliar plot had the highest diversity indices (both Shannon’s H’ and Simpson’s 1/D). All specimens collected at GLR&D were donated to the Frost Entomological Museum at the University Park campus of Penn State.

Goal: Conduct breeding bird singing surveys for birds at SGL 33 and SGL 103 sites. Singing surveys at SGL 103 will be supplemented with bird productivity (nesting success) research. This bird productivity data at SGL 103 will provide a needed year of data midway through a vegetation treatment cycle at that study site.

Completed as follows: We detected between 19-26 breeding bird species within the wire and border zones at SGL 33 and between 10-13 species on the ROW sections at SGL 103. The most abundant birds at all study areas included early successional habitat obligates such as chestnut-sided warbler, common yellowthroat, eastern towhee, field sparrow, indigo bunting, and gray catbird. These are all species of native, neotropical migrants that are declining throughout their range in the mid-Atlantic.

Productivity research on breeding birds was not conducted at SGL 103. This is because the SGL 103 right-of-way was unexpectedly managed. The management was done because remotely collected data indicated that the vegetation clearances from the electric transmission wires were not sufficient. As a result, the border zone was cut back; significantly affecting the vegetation along the ROW. This change disrupted the breeding birds and collecting productivity data would be misleading.

Goal: Conduct timed-area count survey for snakes at GLR&D area. Substrate and habitat use will be noted and implications for ROW management addressed based upon species of snakes detected.

Completed as follows: We observed 7 species (13 individuals) of reptiles and amphibians during our surveys at GLR&D; one salamander, one toad, two frogs, one turtle, and two snake species. Mowing with herbicide plots had the highest abundance and richness of amphibians and reptiles. Northern black racer and eastern box turtle were the most abundant species encountered. The mow-only site contained fewer reptiles and amphibians than sites managed using IVM. In addition, a paper was published on this work (see #7 below):

Goal: Develop Lepidopteran protocol in conjunction with the Frost Museum and Center for Pollinator Research at The Pennsylvania State University. This protocol will address capture and identification techniques, voucher collection, and standardization of effort across our study sites. The protocol was developed and implemented in field seasons 2022 and 2023.

Completed as follows: A total of 264 butterflies and skippers were collected from the five plots at SGL33. Overall, most butterflies and skippers were collected at the low-volume foliar plot (n=78) and the fewest at the mow only plot (n=29). Tentatively a total of 35 butterfly and skipper taxa were collected at all sites in Centre County in 2023. The most abundant taxon for all of 2023 at SGL33 was Megisto cymela cymela (Little Wood Satyr butterfly, n=28). A total of 30 butterflies and skippers were collected from the two plots at SGL103—both plots managed using integrated vegetation management (with selective herbicide application). Tentatively a total of 11 butterfly and skipper taxa were collected in 2023 at SGL103. The most abundant taxon for all of 2023 at SGL103 was Coenonympha tullia inornata (Common Ringlet butterfly, n=6).

Goal: Conduct vegetation surveys at all locations to document vegetation community and species richness. These periodic vegetation surveys permit us to document plant response to IVM and to identify rare plant species and potentially invasive non-native species. These plant surveys also assist our research partners in identifying non-compatible vegetation in the ROW.

Completed as follows: We found that the richness of native flowering plants did not differ between plots treated with an IVM herbicide approach and those that were mechanically treated. However, mechanically treated plots had significantly higher abundance of non-compatible overstory trees than IVM plots. IVM plots generally supported a forb (versus shrub) cover type that may be resistant to tree invasion. Our study indicates that long-term IVM approaches support native flowering plant species richness while achieving the goal of a stable, compatible plant community type under electric transmission line rights-of-way.

TREE Fund Webinar Series Presentation: Integrated Vegetation Management on Electric Transmission Lines Rights-of-Way: Effects on Ground Beetles, Vegetation, and Native Birds. State Game Lands 33 research update. April 2025

Year: 2021-2024

Funding Duration: 3 year

Grant Program: Sponsored Grant

Grant Title: Long term effects of electrical right-of-way vegetation management on floral and faunal communities

Researcher: Dr. Carolyn G. Mahan