An Assessment of Eastern Hemlock Crown Dynamics 10-years After Thinning on the Allegheny Plateau, Pennsylvania
| Authors: | Mary Ann Fajvan, Andrea T. Hille |
| Year: | 2023 |
| Type: | Proceedings - Paper |
| Station: | Northern Research Station |
| DOI: | https://doi.org/10.2737/NRS-GTR-P-211-paper28 |
| Source: | In: Kern, Christel C.; Dickinson, Yvette L., eds. Proceedings of the first biennial Northern Hardwood Conference 2021: Bridging science and management for the future. Gen. Tech. Rep. NRS-P-211. Madison, WI: U.S. Department of Agriculture, Forest Service, Northern Research Station: 136–146. |
Abstract
Hemlock woolly adelgid (HWA) threatens the existence of eastern hemlock trees and associated ecosystems. We propose that increasing canopy light exposure via silvicultural thinning can reduce hemlock’s vulnerability to HWA. Four, overstocked stands on the Allegheny National Forest were selected for thinning. There was no HWA infestation and half of each stand was thinned. Thirty circular plots per stand were established surrounding a hemlock targeted for crown release on 3 to 4 sides. Similar criteria were used to select hemlocks in 30 untreated plots. We visited subject trees prethinning, and 5 and 10 years post thinning; diameter, total height, live crown ratio, and crown area were measured on 246 trees. Temporal changes in diameter were not significant between treatments but trees in thinned plots averaged 5 cm larger after 10 years. Live crown ratio was maintained in thinned stands and decreased after year 5 in controls. Crown area increased in thinned plots and decreased in controls.