Plant Community Research

Key Findings in Plant Communities: Post-2016

In 2016, native plant species richness and non-compatible tree density was calculated within the wire zone area of research plots at SGL 33. Instead of examining these variables according to treatment type, we examined these variables in relation to the amount of herbicide used to treat the sites in 2012. In addition, we compared mechanical to chemical treatments in general. Like earlier studies, we found that herbicides significantly reduced the number of non-compatible tree species in the wire zone when compared to mechanical (mowing or handcutting) treatments. We also focused our analysis on compatible, native species of plants and found that species richness did not differ among plots that were mechanically or chemically treated. These recent findings further support the use of integrated vegetation management to control non-compatible tree species while maintaining native plant species richness in rights-of-way.

Findings: Pre-2016

When a transmission right-of-way is initially cleared, a short-term decrease in total vegetative cover occurs. Following tree canopy removal, plants that tolerate high levels of sunlight increase in dominance, and tree seeds present in the soil germinate and grow. Thus, follow-up management is necessary to maintain a low-growing plant community to optimize safe and reliable transmission of electricity.

Data collected from SGL33 and GLR&D sites indicate that herbicide treatments to remove incompatible species (e.g., tall-statured trees) produce a distinct change in the plant community. Post-treatment vegetative cover ranges from grasses, to herbicide-tolerant wildflowers, shrubs and small trees. These new plant communities are relatively stable and have diversity that equals or exceeds non-treated areas.

The data also shows that right-of-way vegetation managers can predict cover types and develop the kind of vegetation desired in a particular situation by prescribing appropriate maintenance. Management units that were treated with herbicides alone or in combination with mowing had fewer incompatible trees per acre within the wire zone compared to units with mowing alone or hand-cutting treatments Table 3. The diverse plant community created within the right-of-way as the result of vegetation management practices Table 1 produces a variety of native species important for wildlife food and cover Table 2 and Table 4.

Key Findings

1. Plant communities can be changed with the use of an appropriate herbicide and application method. 23618202425262734
2. Vegetation management practices that include the use of selective herbicides result in diverse vegetation that provides forage and habitat for wildlife on rights-of-way. 2141820
3. Plant communities can be created that inhibit tree establishment, thereby reducing maintenance costs for utility companies and mitigating the potential for power outage. 5
4. Integrated vegetation management that combines a variety of application methods (e.g., low volume basal bark, high volume foliar) and herbicides is more effective at limiting non-compatible woody vegetation than mechanical methods (e.g., hand-cutting, mowing).
5. Over 120 species of plants have been documented on the right-of-way project area with plant species richness as high on herbicide-treated as mechanically-treated sites.

Table 4

Number of plant species present in the wire and border zones with various integrated vegetation management practices on the State Game Lands 33 Project Area.

References

2Bramble WC and WR Byrnes. 1983. Thirty years of research on development of plant cover on an electric transmission right-of-way. J. Arboric. 9(3):67-74.⤴

3Bramble WC and WR Byrnes. 1996. Integrated vegetation management of an electric utility right-of-way ecosystem. Down to Earth 51(1):29-34.⤴

5Bramble WC, WR Byrnes, and RJ Hutnik. 1990. Resistance of plant cover types to tree seedlings invasion on an electric transmission right-of-way. J. Arboric. 16(5):130-135. ⤴

6Bramble WC, WR Byrnes, RJ Hutnik, and SA Liscinsky. 1991. Prediction of cover type on rights-of-way after maintenance treatments. J. Arboric. 17(2):38-43.⤴

14Geier RL, S Guggenmoos, and N Theissen. 1992. Ecological aspects of herbicide usage on power line rights-of-way. J. Arboriculture 18(4). 209-215. ⤴

18Yahner RH. 2004. Wildlife response to more than 50 years of vegetation maintenance on a Pennsylvania, U.S., right-of-way. J. Arboric. 30 (2):123-126. ⤴

20Yahner RH. 2006. Wildlife habitat, herbicides, and rights-of-way maintenance-integrated vegetation management and the wire-border zone method. Natural Areas Journal 26:114-115. ⤴

24Yahner RH, WC Bramble, and WR Byrnes. 2001. Response of amphibian and reptile populations to vegetation maintenance of an electric transmission line right-of-way. J. Arboric. 27(4):215-221. ⤴

25Yahner RH and RJ Hutnik. 2005. Integrated vegetation management on an electric transmission right-of-way in southeastern Pennsylvania, U.S. J. Arboric. 31(5): 263-268. ⤴

26Yahner RH and RJ Hutnik. 2005. A 15-year follow-up to vegetation on an electric transmission right-of-way in southeastern Pennsylvania. J. of the Pennsylvania Academy of Science 79:72-74. ⤴

27Yahner RH and RJ Hutnik. 2005. Plant species richness on an electric transmission right-of-way using integrated vegetation management. J. Arboric. 31(3):124-130. ⤴

34Yahner RH, RT Yahner, and BD Ross. 2008. Plant species richness at the Green Lane Research and Demonstration Project Pennsylvania,U.S. J. Arboric. & Urban Forestry 34(4):238-244. ⤴