Succession and disturbance in an endangered red spruce−Fraser fir forest in the southern Appalachian Mountains, North Carolina, USA

Abstract

Red spruce-Fraser fir forests are geographically limited to high elevations in the Appalachian Mountains (USA) and are considered to be endangered in the USA. We investigated the successional status and radial growth patterns in the heavily disturbed red spruce Picea rubens Sarg. and Fraser fir Abies fraseri (Pursh) Poir. forest of Roan Mountain, Tennessee and North Carolina. This study elucidates the complexity of second-growth red spruce development after logging and disturbances by balsam woolly adelgid Adelges piceae Ratz. We documented precise temporal information of stand age, disturbance regimes, recruitment patterns, and the successional trajectory of the spruce-fir forest community. We used radial growth patterns of red spruce samples to detect the frequency and magnitude of disturbance. Red spruce was the oldest dominant canopy species, although Fraser fir had high recruitment rates over the past 80 yr. Changes in forest structure and species richness coincided with stand-wide disturbance events such as balsam woolly adelgid infestation and widespread early twentieth-century logging. The competitive advantage of Fraser fir over red spruce has resulted in an even-aged Fraser fir-dominant forest that occupies a relatively early stage of successional development. This study provides a 130 yr environmental history to assist land managers in the southern Appalachian Mountains as they develop long-term restoration plans for this unique ecosystem.