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1 March 2011 Effects of Power-Line Maintenance on Forest Structure in a Fragmented Urban Forest, Raleigh, NC
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With the increase in urban development, forest fragments are becoming more prevalent. In urban areas, there is a tendency to hide power-lines within or on the edges of these fragmented forests; however, it is unknown how the maintenance of vegetation under and along power-lines impacts the forest composition and structure of an adjacent fragmented, urban forest. An urban, fragmented maple-oak-hickory forest is located on the Meredith College campus, Raleigh, NC. A 1-ha plot with a hundred 10- × 10-m subplots was established in 2007 to initiate a long-term project supporting undergraduate research. An adjacent meadow is cut and maintained regularly up to the forest and plot edge for power-line clearance and access. We identified, tagged, and measured all of the trees with a diameter at breast height (DBH) ≥ 5 cm in this permanent plot, and compared the tree species richness (S), Shannon-Weiner diversity index (H), Sorenson's similarity index (Ss), DBH, stem density, and basal area along the 100-m gradient from the forest edge. We also used a non-metric multidimensional scaling (NMS) analysis to describe how species composition changed along the gradient. Our findings showed that S, H, and Ss did not change along the 100-m gradient. The NMS confirmed that species composition was not different in the edge subplots (0–10 m from edge) compared to all other subplots and therefore was not impacted by continual, local disturbance along forest edges. However, we found that forest structure changed along the gradient with the exception of mean DBH; stem density and total basal area varied along the 100-m gradient. There was greater stem density along the edge of the forest (0–5 m and 10–20 m from edge) compared to the other interior subplots. Some of the interior subplots (10–20 m and 60–70 m from the edge) had a higher total basal area than the remaining plots. As expected, we also found that there was a negative linear relationship between DBH and stem density for all subplots. Our results confirm trends found in previous studies that community structure parameters (stand density and basal area) differ between forest edges and their respective forest interiors, but did not agree with previous research, which found species composition to be affected by edges. We believe the regular pruning of the forest edge adjacent to the power-lines explains our observed differences in forest structure, but tree species richness, diversity, similarity, and composition may be determined by the disturbance of larger-scale ecological processes. Our results show how power-line placement within a fragmented urban forest can affect the structure of the adjacent forest, and we recommend that the ecological effects of power-line corridors should be further investigated and incorporated into the larger body of literature on forest fragmentation.

Amanda S. Powell and Erin S. Lindquist "Effects of Power-Line Maintenance on Forest Structure in a Fragmented Urban Forest, Raleigh, NC," Southeastern Naturalist 10(1), 25-38, (1 March 2011).
Published: 1 March 2011

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