Hemlock Seedling Survival and Growth across Silvicultural Light Gradients: Implications for Forest Restoration

The invasive hemlock woolly adelgid (Adelges tsugae Annand) continues to threaten the survival of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) in eastern North America. Effective restoration efforts will require an integrated understanding of how these species respond to management interventions under current environmental pressures. This study examined the early growth, survival, and pest resilience of eastern and Carolina hemlock seedlings planted under varying competition control, insecticide treatment, and light availability regimes. Seedlings planted along canopy gap transects (northern edge, center, southern edge) exhibited consistently greater height (99.78 ± 0.85 cm) and basal diameter growth (15.50 ± 0.15 mm) compared to those in adjacent forest interior plots (57.84 ± 0.93 cm and 9.60 ± 0.16 mm, respectively), highlighting the positive influence of increased light availability on early performance. Growth and survival were highest along the northern edge of gaps, likely due to favorable light conditions combined with reduced competition from surrounding vegetation. Together, the results underscore the importance of targeted competition management, localized site assessments, and integrated pest management strategies in supporting hemlock restoration.