Influence of Historic Upland Silviculture on the Composition of Ravine Forests along the Apalachicola River, Florida, USA

摘要

The ravines along the Apalachicola River are recognized for their species-rich mixed hardwood forests. Although steep slopes may have limited logging, much of the surrounding sandhill and scrub uplands were extensively modified for silviculture in the late 1950's. We examined how contrasts in the intensity of historic upland silviculture have influenced present-day woody species composition in ravine slope forests. To maximize ravine differences due to upland silvicultural intensities while concurrently minimizing the potentially confounding influences of aspect and slope angle, ravine sampling areas were delineated using a combination of historical air photos, field reconnaissance, and a digital elevation model. Ordination (principal coordinates analysis) and permutation-based tests of group differences (multiple response permutation procedures) confirmed that where uplands were selectively-cut longleaf pinelands, tree composition on neighboring ravine slopes was dominated by three species: Quercus hemisphaerica Bartr., Pinus glabra Walt., and Quercus alba L. By contrast, where the uplands had undergone intensive mechanical site preparation for slash pine cultivation, only one species, Quercus hemisphaerica, was dominant. Intensive upland silviculture was also correlated with a decreased importance of Fagus grandifolia, a species identified as a major constituent of presettlement ravine forests. We discuss how fire suppression, geomorphic disturbance, and logging along upper ravine slopes may explain these compositional differences.