Exploring natural and artificial regeneration techniques for developing high-quality bottomland oak stands

Abstract

Bottomland hardwood forests of the southeastern United States are among the most diverse and productive in the country. In the past, many of these areas were not managed soundly for timber production and, as a result, are currently stocked with a variety of species that are commercially less valuable than oak. Naturally regenerating oak in bottomland forests is problematic because large advance reproduction is absent in the understory, and the silvicultural techniques that favor oak development encourage the growth of problematic species such as Rubus spp., Vitis spp., Smilax spp., and Arundinaria spp. These and other shade-tolerant woody and herbaceous species deprive oak of light during critical periods of establishment, often causing them to die. This study examines the impacts of pre-harvest treatments applied one year in advance of vi overstory removal to determine if this is a sufficient amount of time to establish natural oak reproduction when there is a good acorn crop, or if this is enough time to allow artificially regenerated seedlings to overcome transplant shock such that they can be competitive once the overstory is removed. Also examined were various types of browse protection and fertilization on the growth and establishment of seedlings planted after a commercial clearcut. Our findings indicate that preharvest treatments to increase understory light levels and decrease the abundance of vines prior to overstory removal is essential for increasing the stocking and competitive stature of naturally regenerated oak seedlings. Underplanting oak prior to overstory removal is a viable option to increase stocking and/or control spatial distribution of desirable stems. Where pre-harvest regeneration planning is not a viable option, the site should be clearcut and some measure of site preparation employed. Planted seedlings should be fertilized and protected using plastic tree shelters. Not only do seedlings become established more rapidly, but their form is far superior to those open-grown or in wire tree shelters. Initial planting costs are higher for such cultural treatments, but the cost per established seedling is less than those unprotected or encircled by wire shelters and will result in shorter rotations.