Plant Species Richness On An Electric Transmission Right-Of-Way Using Integrated Vegetation Management

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 stem­foliage 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.