Response of Amphibian And Reptile Populations to Vegetation Maintenance of An Electric Transmission Line Right-Of-Way

Diversity and Relative Abundance on ROW Versus Adjacent Forest

Eight species of amphibians and reptiles were observed during the study (Table 1). All eight species were found on the ROW, whereas only two species occurred in the adjacent forest. These included 123 observations of one toad species, three salamander species, three snake species, and one turtle species. Because animals observed were not permanently marked for individual recognition, the same individual may have been observed more than once, but sampling periods were spaced at least 2 to 3 weeks to minimize recounting the same individual.

The four most common species in decreasing order of relative abundance were Jefferson salamanders (Ambystoma jeffersonianum) (n = 77 observations, or 62.6% of total) (Figure 3), redback salamanders (Plethodon cinereus) (n — 33, 26.8%), northern ringneck snakes (Diadophis punctatus eduwardsii) and eastern box turtles (Terrapene Carolina Carolina) (n = 3 each, 2.4%) (Table 1). In the study of amphibian and reptile populations on the State Game Lands 33 ROW in central Pennsylvania (Yahner et al. 2001) and in other studies of terrestrial salamander populations throughout the northeastern United States (e.g., DeGraaf and Yamasaki 1992; Rodewald and Yahner 1999), the redback salamander was the most abundant species. However, the Green Lane ROW was characterized by relatively flat terrain and had numerous standing pools of water, so it was a very suitable habitat for Jefferson salamanders.

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Figure 3.

Two Jefferson salamanders beneath a large coverboard in the wire zone of a foliage spray unit. The Jefferson salamander was the most common salamander found on the ROW and in the adjacent forest. This is a large salamander, which is usually at least 10 cm (4 in.) long. It typically prefers damp woods near water and feeds on a variety of insects, grubs, and earthworms (photo taken by RHY in March 2000).

A relatively similar number of salamanders were observed on the ROW (n = 58, 51.8%) and in the adjacent forest (n = 54, 48.2%) (Table 1). Based on the number of coverboards on the ROW versus in the forest (30 versus 10, respectively), only 28 individual salamanders would be expected in the forest. More salamanders occurred in the forest than on the ROW because they require moist microclimatic conditions for foraging and breeding (Shaffer 1991). In contrast, snakes were found exclusively on the ROW, which provided a combination of shrubby and grassy habitat for these species. Similarly, snakes were noted only on the State Game Lands 33 ROW and not in the adjacent forest in central Pennsylvania (Yahner et al. 2001).

In contrast to State Game Lands 33 ROW (Yahner et al. 2001), three species did not occur on the Green Lane ROW These included the eastern smooth green snake (Opheodrys vernalis vernalis), mountain earth snake (Virginia valeriae pulchra), and northern redbelly snake (Storeria occipitomaculata occipitomaculata). The mountain earth snake is restricted to the mountainous areas of Pennsylvania (Shaffer 1991) and, therefore, is not expected to be found on the Green Lane ROW. Moreover, eastern box turtles were absent from the mountainous areas of the state (Shaffer 1991) and, hence, did not occur on the State Game Lands 33 ROW

Diversity and Relative Abundance per Treatment Unit

Sixty-nine observations of amphibians and reptiles were recorded in the five treatment units on the Green Lane ROW (Table 2). The most common species was the Jefferson salamander (n = 38 observations, 55.1% of total), followed by the redback salamander (n = 19, 27.5% of total) and the eastern box turtle and northern ringneck snake (n = 3 each, 4.3%). Of these 69 observations, only six were made prior to treatment in June 1999: one American toad (Bufo americanus americanus), one eastern garter snake (Thamnopnis sirtalis sirtalis), one ringneck snake, and three box turtles. Thus, the remaining 63 individuals were observed subsequent to the treatments.

The number of species per treatment unit varied from six species in the mowing plus herbicide unit to three each in the stem—foliage and foliage spray units (Table 2). Eighteen and 17 observations of amphibians and reptiles were found in the handcutting and stem-foliage spray units, respectively; 11 to 12 observations were found in mowing, mowing plus herbicide, and foliage spray units. All units, including handcutting, were relatively heterogeneous in cover types, thereby providing a diversity of habitat for amphibian and reptile species. In contrast, the handcutting unit on the State Game Lands ROW was relatively homogeneous (tree cover type), which was similar to young, even-aged stands that are of little value to amphibian and reptiles as habitat (Rodewald and Yahner 1999;Yahner et al. 2001).

Diversity and Relative Abundance in Wire Versus Border Zones

Eight and five species of amphibians and reptiles, respectively, were recorded in wire and border zones on the ROW (Table 3). These include 38 (55.1%) observations in wire zones and 31 (44.9%) in border zones. Furthermore, a slightly greater number of salamander observations was noted in wire zones (n = 31, 53.4%) than in border zones (n = 27, 46.6%).This may be attributed in part to relatively wet conditions created throughout wire zones of the ROW after rains. In contrast, salamanders were less common in wire zones compared to border zones on the State Game Lands 33 ROW (Yahner et al. 2001).