Presettlement forests and fire in southern Alabama

Abstract

Although the loss of Pinus palustris P. Mill. (longleaf pine) dominated communities and the alteration of the presettlement fire regimes have been documented, there is little information on the ecology of the presettlement lower Coastal Plain forests of the southeastern United States. We used 12 637 witness trees, which were recorded by General Land Office surveyors between 1820 and 1846, to identify presettlement witness tree associations and to explore witness tree – environmental variable relationships. Detrended correspondence analysis (DCA) was used to identify three witness tree associations including a Pinus spp. – Quercus marilandica (L.) Muenchh. association, a Quercus spp. – Carya spp. association, and a Persea spp. – Fagus grandifolia Ehrh. association. Canonical correspondence analysis and contingency tables were used to describe and test witness tree relationships with slope, elevation, and soil drainage. Additionally, bearing distances, used as an indicator of forest density, were compared among the witness tree associations. Species orientation shown by the DCA ordination diagram was interpreted as a gradient of fire frequency. This interpretation of a fire gradient was supported through the analysis of bearing distances, which showed high bearing distances associated with witness trees located on the high fire frequency end of the gradient. The relationships between witness trees and environmental variables as well as relationships between witness trees and bearing distances suggest that fire-dependent longleaf communities dominated the presettlement study area.