Tree Species Response to Clear-cutting a Southern Appalachian Watershed

Abstract

A 16. 1-ha watershed was experimentally clear-cut in 1939 and again in 1962. All material over 1 cm in diam was cut and left in place, thereby minimizing soil disturbance. Density data collected on permanent quadrats before cutting, 13 years after the first cut and 15 years following the second cut, indicate vegetation response varies by species and physiographic position. There was also a difference in response between the two clear-cuts. There was little change in number of tree species found per unit area following the two clear-cuts. However, certain species such as Liriodendron tulipifera became much more abundant while others decreased in abundance especially on lower slope to cove and mid to upper N and E physiographic positions following the second cut. INTRODUCTION Disturbances, such as clear-cut harvesting, in the eastern deciduous forest ecosystem change the relative composition of tree species (Oliver, 1980). For example, Liriodendron tulipifera has been shown to increase in density relative to other species following clear-cutting throughout most of the eastern United States (Swank and Helvey, 1970; Kovner, 1957; Merz and Boyce, 1958; Potzger and Friesner, 1934). Seed source, vegetative and advanced reproduction, site characteristics and time of year are important factors determining compositional changes of forest stands following disturbance. Many tree species regenerate by stump or root sprouts or from seedlings already on the ground while others originate from stored seed pools (McGee and Hooper, 1970; Roach, 1962; Marks, 1974). Autumn and winter clear-cut harvesting has been shown to increase establishment of Liriodendron tulipifera seedlings (Trimble and Tryon, 1969). The degree of disturbance appears to be more important in influencing species change than either topography or aspect for much of the eastern United States (Merz and Boyce, 1958; Roach, 1962). Liriodendron tulipifera has been observed to spread across the moisture gradient from stream valleys to dry ridges in southern Indiana following clear-cut harvests on the Hoosier National Forest. This apparently is not true for central and northern hardwood forests of the Appalachian Mountains (Trimble and Hart, 1961). The length of time these composition changes remain for various positions along the moisture gradient has not been fully studied (Collins, 1962; Cristofolini and Cristofolini, 1967; Levering, 1968). One of the first experimental clear-cuts in the eastern deciduous forest occurred at Coweeta Hydrologic Laboratory in the southern Appalachians. A 16.1-ha watershed (WS13) was clear-cut in 1939 and again in 1962. These cuts are different from a commercial clear-cut because no material was removed from the site, thereby eliminating skid trails and logging roads. 1 Contribution from Purdue Univ. Agr. Expt. Sta. Paper No. 6851. Research supported in part by the Southeastern Forest Experiment Station, USDA and in part by National Science Foundation Grant No. DEB-8012093.