Canopy Disturbance Patterns in Secondary Hardwood Stands on the Highland Rim of Alabama


Justin L. Hart

Additional Authors:

Arvind A.R. Bhuta, Rebecca M. Schneider


March 2011


ABSTRACT Disturbance regimes of many hardwood forests of the eastern United States in the complex stage of development are characterized by localized canopy disturbance events that change fine-scale biophysical conditions. Recently, research has demonstrated the importance of gap-scale disturbance processes in secondary hardwood stands of the southern Appalachian Highlands. However, information on canopy disturbance patterns during early developmental stages is required from the broader geographic region for a comprehensive understanding of stand dynamics. The goal of this study was to reconstruct canopy disturbance history for mixed hardwood stands on the Highland Rim of Alabama to elucidate disturbance patterns during early development. We analyzed radial growth from 46 Quercus individuals to reconstruct canopy disturbance history. The majority (67%) of the trees analyzed exhibited release events. In total, 42 releases were detected and some trees experienced multiple events. Of these releases, 28 (67%) were classed as minor and 14 (33%) were classed as major. Mean release duration was 4.00 years 6 0.21 (SE) and the longest release was sustained for eight years. Based on mean release duration, we speculate that most of the canopy gaps were filled by lateral crown expansion rather than subcanopy height growth. We did not document any forest-wide disturbance events; a pattern that may be a regional phenomenon or may be related to forest age. Canopy disturbances became common after ca. 40 years of development. We propose that the frequency of canopy gaps will decrease and the size and magnitude of individual gaps will increase as the stands mature.