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Research ArticleArticles

Plant Species Richness on an Electric Transmission Right-Of–Way Using Integrated Vegetation Management

Richard H. Yahner and Russell J. Hutnik
Arboriculture & Urban Forestry (AUF) May 2005, 31 (3) 124-130; DOI: https://doi.org/10.48044/jauf.2005.31.3.124
Richard H. Yahner
*School of Forest Resources, The Pennsylvania State University, University Park, PA, 16802, U.S.
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Russell J. Hutnik
*School of Forest Resources, The Pennsylvania State University, University Park, PA, 16802, U.S.
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Abstract

The State Game Lands (SGL) 33 Research and Demonstration Area, Centre County, Pennsylvania, U.S., has been studied each year since 1953, making this 52-year old project extremely valuable as a source of information on the effects of mechanical and herbicidal maintenance on flora and fauna along an electric transmission right-of-way (ROW). A desired objective of integrated vegetation management on the SGL 33 Research and Demonstration Area is to create a diversity of plant species. In this paper, our objective was to document plant species richness among treatment units and in relation to wire and border zones on the SGL 33 Research and Demonstration Area. We noted the presence of plant species from late May through mid-August in both 2003 and 2004 and observed 125 vascular plant species in the 15 treatment units. The total number of species per unit ranged from a low of 35 species in a mowing unit to a high of 63 species in a basal low-volume spray unit. Of the total number of plant species found on the right-of-way, 95 (76%) and 110 (88%) occurred in wire and border zones, respectively. In wire zones, the average number of plant species ranged from 31 in mowing units to 41 in stem–foliage spray units. In border zones, the average number of plant species varied from a low of 34 in mowing units to a high of 41 in handcut units. The proportion of exotic species did not vary appreciably between wire and border zones (19% and 22% of total, respectively) on the ROW. However, the three units adjacent to unpaved state forest roads with high rates vehicular traffic not only had the highest number of total species in the unit (55 to 63 species) but also the highest number of exotic species (13 to 16 species). Hence, vehicular traffic and roadside management may be responsible in part for the invasion of seeds or other means of plant dispersal to these units. Because units relatively isolated from state forest roads tended to have fewer exotic species, these sections of the ROW can serve as refugia for native flora.

Key Words
  • Exotic species
  • herbicides
  • integrated vegetation management
  • rights-of-way
  • species richness
  • tree control
  • vegetation

A major goal of the State Game Lands (SGL) 33 Research and Demonstration Project in central Pennsylvania, U.S., since 1987 has been to determine the use of Integrated Vegetation Management (IVM) for maintenance of an electric utility transmission right-of-way (ROW) (Bramble and Byrnes 1996; Yahner and Hutnik 2004a). The response of vegetation to IVM is important because plant communities can change within a relatively short time as a result of natural plant succession.

The IVM technique for vegetation along a ROW involves two phases: (1) the use of a herbicidal spray or mechanical treatment to initially control the density of target (undesirable) trees (i.e., those that have the potential of growing to a height that is not compatible with safe ROW maintenance) and (2) the development of a tree-resistant plant cover type to reduce target tree invasion of the ROW (Bramble and Byrnes 1996; Yahner and Hutnik 2004a). The wire–border zone method was used on all treatment units of the SGL 33 Research and Demonstration Project as a means of achieving this goal (Figure 1).

Figure 1.
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Figure 1.

Diagram of a 230-kV electric transmission line, showing wire and border zone. A combination of a low-growing, forb–shrub–grass cover type develops in the wire zone, and a tall shrub cover type occurs in the border zone. Adjacent to the border zone is mature forest.

The SGL 33 Research and Demonstration Area has been studied each year since 1953, making this 52-year-old project extremely valuable as a source of information on the effects of mechanical and herbicidal maintenance on flora and fauna along an electric transmission ROW (Yahner and Hutnik 2004a, 2004b). A desired objective of IVM on the SGL 33 Research and Demonstration Area is to create a diversity of plant species, which in turn provides a diverse wildlife habitat (Yahner and Hutnik 2004a). On a broad scale, habitat diversity on the ROW is achieved by herbicidal and mechanical maintenance of treatment units via the wire–border zone method. However, on a smaller scale, plant species diversity also is achieved by the presence of different combinations of shrub, forb, and grass cover types.

In this paper, our objective was to document plant species richness among treatment units and in relation to wire and border zones on the SGL 33 Research and Demonstration Area. Species richness is a simple, yet important, measurement of species diversity and can be defined as the total number of different species in a given area (Yahner 2000).

STUDY AREA AND METHODS

The study area consists of 15 units, each of which was given a major treatment (mowing, mowing plus herbicide; stem–foliage spray; foliage spray; basal low-volume spray; and handcut) (Table 1) in 1987, 1993, 1996, and 2000 (see Yahner and Hutnik 2004a, 2004b for details of the treatments). Each treatment unit is rectangular in shape, ranges from 0.8 to 1.7 ha (2 to 4.2 ac), and spans the width of the ROW.

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Table 1.

The total number of plant species in wire and border zones of 15 treatment units at the State Game Lands 33 Research and Demonstration Area from late May through mid-August 2003 and 2004. The number of exotic species is given in parentheses.

As part of the vegetation assessment of treatment units of plant species from late May through mid-August in both 2003 and 2004, the presence of each plant species was noted relative to wire versus border zone in each treatment unit. Only plants located at least 3 m (10 ft) from a forest access road arbitrarily were surveyed, thereby eliminating the counting of species immediately on the road edge.

RESULTS AND DISCUSSION

We observed 125 vascular plant species in the 15 treatment units on the SGL 33 Research and Demonstration Area during the 2 years (Table 1 and appendix). The total number of species per unit ranged from 35 species in a mowing unit (M-1) to 63 species in a basal low-volume unit (BLV-3) (Figure 2).

Figure 2.
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Figure 2.

A basal low-volume spray unit (BLV-3). Note the diversity of plant species in this unit (photo credit: R. Yahner, July 2003).

Another unit with a high number of plant species was a handcut unit (HC-2), which also was quite heterogeneous in plant structure (Table 1 and appendix). Two reasons for this heterogeneity is that this unit was originally a mowing unit and is in the process of being converted to a handcut unit (Yahner and Hutnik 2004b). Hence, it has mowed areas on one portion and woody areas on another portion of the wire zone, which was quite rocky and difficult for a mower to treat the unit. Furthermore, the southern portion of this unit was once traversed by an unimproved dirt road, which likely facilitated dispersal of seeds into this area.

Of the total number of plant species found on the ROW, 95 (76%) and 110 (88%) occurred in wire and border zones, respectively (Table 1 and appendix). In wire zones, the average number of plant species ranged from 31 in mowing units to 41 in stem–foliage spray units. In border zones, the average number of plant species varied from a low of 34 in mowing units to a high of 41 in handcut units. Fourteen species were found only in wire zones, whereas 27 species were exclusive to border zones. Only five species occurred in all 15 units.

Of the total number of plant species, 23% were exotic species (Table 1 and appendix). This number is similar to 20% exotic plant species noted in unfragmented forest stands in Wisconsin (Rooney et al. 2004).

The proportion of exotic species did not vary appreciably between wire and border zones (19% and 22% of total, respectively) on the ROW (Table 1 and appendix). However, the three units adjacent to unpaved state forest roads with high rates of vehicular traffic (SF-2 and MH-3 adjacent to Hannah Furnace Road, BLV-3 bisected by Strawband Beaver Road) not only had the highest number of total species in the unit (55 to 63 species) but also the highest number of exotic species (13 to 16 species). Hence, vehicular traffic and roadside management (and perhaps disposal of unwanted landscape clippings and plants along the roadside) may be responsible in part for the invasion of seeds or other means of plant dispersal to these units. Other studies have found that exotic species were more common in forests and grassland near habitat edges, such as those at a road interface (Brothers and Spingarn 1992; Tyser and Worley 1992; Watkins et al. 2003; Pauchard and Alaback 2004). If forest roads in our study were paved, the number of exotic plant species could have been higher (Lundgren et al. 2004). Because units relatively isolated from state forest roads tended to have fewer exotic species, these sections of the ROW can serve as refugia for native flora (after Strittholt and DellaSalla 2001).

Acknowledgments

Cooperators were Asplundh Expert Tree Company, Dow AgroSciences, FirstEnergy (Penelec), and the Pennsylvania Game Commission. Thanks to R.T. Yahner for field assistance and to E. Hill for assistance in preparing the manuscript.

APPENDIX

The table on the following pages contains a list plant species (in phylogenetic order) noted in wire zones (W), border zones (B), in both zones (WB), or absent (——) in 15 treatment units on the State Game Lands 33 Research and Demonstration Area from late May through mid-August 2003 and 2004. The replication of each treatment is given after each unit, where treatments are mowing (M), mowing plus herbicide (MH), stem–foliage spray (SF), foliage spray (F), basal low-volume (BLV), and handcut (HC). Scientific names are taken from Rhoades and Klein (1993).

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  • © 2005, International Society of Arboriculture. All rights reserved.

LITERATURE CITED

  1. ↵
    1. Bramble, W.C., and
    2. W.R. Byrnes
    . 1996. Integrated vegetation management of an electric utility right-of-way ecosystem. Down to Earth 51(1): 29–34.
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    1. Brothers, T.S., and
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    . 1992. Forest fragmentation and alien plant invasion of central Indiana old-growth forests. Conserv. Biol. 6: 91–100.
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    1. Lundgren, M.R.,
    2. C.J. Small, and
    3. G.D. Dreyer
    . 2004. Influence of land use and site characteristics on invasive plant abundance in the Quinebaug Highlands of southern New England. Northeast. Nat. 11: 313–322.
    OpenUrl
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    1. Pauchard, A., and
    2. P.B. Alaback
    . 2004. Influence of elevation, land use, and landscape context on patterns of alien plant invasions along roadsides in protected areas of south-central Chile. Conserv. Biol. 18: 238–248.
    OpenUrlCrossRef
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    1. Rhoads, A.F., and
    2. W.M. Klein, Jr.
    . 1993. The Vascular Flora of Pennsylvania: Annotated Checklist and Atlas. American Philosophical Society, Philadelphia, PA. 636 pp.
  6. ↵
    1. Rooney, T.P,
    2. S.M. Wiegmann,
    3. D.A. Rogers, and
    4. D.M. Waller
    . 2004. Biotic impoverishment and homogenization in unfragmented forest understory communities. Conserv. Biol. 18: 787–798.
    OpenUrlCrossRef
  7. ↵
    1. Strittholt, J.R., and
    2. D.A. DellaSalla
    . 2001. Importance of roadless areas in biodiversity conservation in forested ecosystems: Case study of the Klamath-Siskiyou ecoregion of the United States. Conserv. Biol. 15: 1742–1754.
    OpenUrl
  8. ↵
    1. Tyser, R.W., and
    2. C.A. Worley
    . 1992. Alien flora in grasslands adjacent to road and trail corridors in Glacier National Park, Montana (USA). Conserv. Biol. 6: 253–262.
    OpenUrlCrossRef
  9. ↵
    1. Watkins, R.Z.,
    2. J. Chen,
    3. J. Pickens, and
    4. K.D. Brosofske
    . 2003. Effects of forest roads on understory plants in a managed forested landscape. Conserv. Biol. 17: 411–419.
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  10. ↵
    1. Yahner, R.H.
    2000. Eastern Deciduous Forest: Ecology and Wildlife Conservation (2nd ed.). University of Minnesota Press, St. Paul, MN. 295 pp.
  11. ↵
    1. Yahner, R.H., and
    2. R.J. Hutnik
    . 2004a. Integrated vegetation management on an electric transmission right-of-way in Pennsylvania, U.S. J. Arboric. 30: 295–300.
    OpenUrl
  12. ↵
    1. Yahner, R.H., and
    2. R.J. Hutnik
    . 2004b. State Game Lands 33 Research and Demonstration Project—52 Years of Continuous Study. Annual Report to Cooperators. 33 pp.
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Arboriculture & Urban Forestry (AUF): 31 (3)
Arboriculture & Urban Forestry (AUF)
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May 2005
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Plant Species Richness on an Electric Transmission Right-Of–Way Using Integrated Vegetation Management
Richard H. Yahner, Russell J. Hutnik
Arboriculture & Urban Forestry (AUF) May 2005, 31 (3) 124-130; DOI: 10.48044/jauf.2005.31.3.124

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Plant Species Richness on an Electric Transmission Right-Of–Way Using Integrated Vegetation Management
Richard H. Yahner, Russell J. Hutnik
Arboriculture & Urban Forestry (AUF) May 2005, 31 (3) 124-130; DOI: 10.48044/jauf.2005.31.3.124
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Keywords

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