Land Use History Effects In Mixed Pine - Hardwood Forests at Fort Benning1

Abstract

Over decades, and especially on public lands subject to multiple uses, land use activities can affect forest composition or structure. We asked if current ground layer vegetation composition or stand structure (canopy openness, tree density, plus depth of the soil A layer) in 32 mixed pine-hardwood forest stands at Fort Benning, GA, reflects military use or fire frequency over the last 20 years. The 32 stands, half on sandy and half on clayey soil, were assigned to two military use categories (heavier, open to tracked vehicles, or lighter, with dismounted infantry training) and three fire frequency (# fires/20 yr) categories [low (0–2 fires), medium (3–4 fires), and high (5–6 fires)]. Ordination reflected abundance of grass and legume species, the proportion of pine in the canopy, canopy openness, and tree density and age; it revealed a relatively stronger influence of military land use and canopy composition, and weaker influence of fire frequency (over the past 20 years), on ground layer vegetation differences among the stands. Soil A-horizon depth, abundance of disturbance features, and tree density differed between lighter and heavier military use categories, but not among fire frequency categories. Our results suggest that mechanized military training has led to a loss of topsoil and convergence on abundant pines, grasses, and legumes, while a range of fire frequencies has led to an array of ground layer composition in stands with lighter military use. Under all land use scenarios examined, 70% pine canopy may be favorable for abundant grasses and legumes in ground layer vegetation.