Shortleaf Pine-Hardwood Mixture Establishment and Release in Two Physiographic Regions of Tennessee

Shortleaf pine (Pinus echinata Mill.)-hardwood forest types have been declining in area across shortleaf pine’s native range for at least forty years. Interest in restoring this forest type has increased in recent years, yet knowledge on restoration of mixed shortleaf pine-hardwood forests is limited. The objectives of this study were to investigate five site preparation or release treatments at two sites using different silvicultural systems and their effects on artificially regenerated shortleaf pine (due to the lack of a seed source) and naturally regenerated woody species. The first study investigated establishment and development of even-aged, mixed shortleaf pine-hardwood forests on the Highland Rim physiographic province of Tennessee, whereas the second study investigated establishment and development of two-aged mixed shortleaf pine-hardwood forests after a partial harvest in the Cumberland Mountains physiographic province of Tennessee. At the Highland Rim Site, shortleaf pine was planted at two wide spacings (12x12 and 18x18 ft.) to allow natural regeneration development among the planted pines. Treatments tested included: herbicide and burn (brown-and-burn), burn, herbicide, strip-burn, and a control. Three years after study establishment, statistical differences among treatments occurred for shortleaf pine survival, basal diameter, and height. Survival was greatest in the herbicide treatment and height and basal diameter growth were greatest in the brown-and-burn treatment. Natural regeneration stem densities reflected the intensity of the treatment, and no differences in height were detected. Invasive species such as privet and callery pear were prevalent in most treatments. At the Cumberland Mountains site, shortleaf pine was planted in clusters within canopy gaps at narrow spacings. Treatments investigated at this site included: brown-and-burn, burn, herbicide, scarification, and a control. Two years after planting, no treatment differences were observed for shortleaf pine survival or basal diameter growth, yet seedlings in the scarification treatment were significantly taller than those in the other treatments. Statistical differences for natural regeneration stem densities among treatments were found for cluster interiors, yet not for cluster exteriors. Woody shrubs were prevalent in the regeneration with a minor component of desirable oak species. Both management scenarios offer promise for reintroducing shortleaf pine as a component of mixed stands.