Edaphic Factors and Forest Vegetation in the Piedmont of Virginia

Abstract

FARRELL, J. D. AND S. WARE (Department of Biology, College of William and Mary, Williamsburg, VA 23185). Edaphic factors and forest vegetation in the Piedmont of Virginia. Bull. Torrey Bot. Club 118: 161-169. 1991.-To determine tree species distribution and abundance and possible edaphic factors correlated with these in Piedmont forests, we examined 51 upland hardwood stands in the northern, central, and southern Piedmont of Virginia. Soil Ca, Mg, and pH (but not soil texture) were positively correlated with the first axis of a detrended correspondence analysis (DECORANA) ordination, and % clay, Ca, and Mg were positively correlated with the second axis. Quercus alba was the most abundant species, important in stands all across the ordination and providing the background against which the abundance of other species varied. Quercus prinus, Q. coccinea, Nyssa sylvatica, Liriodendron tulipifera, Q. velutina, Q. rubra, Carya spp., and Fraxinus americana/Ulmus rubra were sequentially arranged along the first axis. Acer rubrum and the much less abundant species Q. falcata and Q. stellata were important at the high percent clay end of the second axis, while Q. coccinea was most important at the low percent clay portion of that axis. In an ordination of the understory layer of the 25 northern Piedmont stands, Liriodendron tulipifera, Acer rubrum, and Nyssa sylvatica were abundant only on the low Ca, low Mg, low pH end of the first axis, and Ulmus rubra, Fraxinus americana, and Cercis canadensis were found at the opposite end of the first axis. Cornusflorida and Carya spp. were spread broadly across the understory ordination, but were most important in its center, with Carya spp. most abundant on Triassic sites. None of the Quercus spp. which were dominant in the overstory were well represented in the understory. In both overstory and understory ordinations the stands at the high Ca, high Mg, high pH end of the first axis were northern Piedmont stands on Triassic formations, a geological substrate uncommon in most of the rest of the Virginia Piedmont. Since the forests of the non-Triassic portions of the Virginia Piedmont have traditionally been classified as oak-(pine)-hickory forests, the high importance of Carya spp. on the more restricted, Ca- and Mg-rich less acid Triassic substrates and their low importance in the areally extensive non-Triassic formations were unexpected.