Structure and Dynamics of an Old-Growth Pine-Oak Community in the Southern Appalachian Mountains, Georgia, U.S.A.

Investigating the composition and structure of old-growth forests provides information about the spatial and temporal variability of processes responsible for stand development, succession, and biogeographic patterns of forests. This study quantifies stand structure in the Marshall Forest Preserve, an old-growth forest remnant located in northwest Georgia. We established forest inventory plots to quantify species composition, stand structure, and successional dynamics. We also analyzed the radial growth patterns of trees to document stand age, recruitment, and the frequency of canopy disturbance within the preserve. The forest was dominated by shortleaf pine (Pinus echinata Mill.) and chestnut oak (Quercus montana Willd.), while red maple (Acer rubrum L.) and mockernut hickory (Carya tomentosa Nutt.) were abundant in the understory. Shortleaf pine was the oldest tree species in the preserve, with the oldest individuals exceeding 220 years in age. A clear successional pattern developed over the 20th century with the establishment of hickory and maple after pine and oak. The major agent of 20th century canopy isturbance was ice storms, which generally resulted in suppression of radial growth in pines and increased radial growth in oaks. Additionally, pulses of understory establishment coincided with major ice storms. The lack of understory disturbance such as fire may be allowing the establishment of shade tolerant understory species while limiting the establishment of pine and oak. Canopy disturbance from ice storms may be accelerating the pace of this compositional shift. Under the current disturbance regime, composition of the preserve is likely to change, leading to an increase in red maple and mockernut hickory and a decline in pine and oak species.