Forests of Small Stream Bottoms in the Coastal Plain of Southwestern Alabama

Abstract

Overstory and understory data were collected from 49 forest stands in 27 small stream bottoms in the Gulf Coastal Plain region of southwestern Alabama. The stands were arranged in a single—dimensioned ordination on the basis of the importance values of the persistent species in the overstories. Leading dominant species, from the dry end to the wet end of the ordination gradient, were Cornus florida, Pinus palustris, Quercus nigra, Liquidambar styraciflua, Nyssa sylvatica v. sylvatica, Magnolia virginiana, and N. sylvatica v. biflora. Two important seral species, most prominent at the middle of the ordination gradient and of relatively little importance at either end, were Pinus elliottii and Liriodendron tulipifera. The stand position on the ordination gradient, referred to as the moisture—regime index, was significantly related to water—table depth, soil—surface gradient, and soil pH at 63.5 cm. Failure to obtain significant relationship with other soil variables was attributed to the high frequency of fresh soil deposition in the small stream bottoms. As a check on the ordination analysis, species—present data were used to construct a species—correlation diagram. When species moisture—regime numbers from the ordination analysis were inserted in this diagram, good agreement was revealed in the results of the two independent analyses.