Crop tree release impacts both the understory and overstory in mixed oak stands of the southern Appalachian Mountains.

Abstract

Crop tree release (CTR) is an intermediate silvicultural treatment that can be used by woodland owners to achieve multiple management goals. Our study addresses a knowledge gap regarding the understory response to CTR in the Appalachian Mountains of southwest Virginia. An increase in understory species composition and abundance is expected, as CTR increases the availability of light and nutrients to the understory. Increased understory growth and abundance can improve habitat for some wildlife species. However, the magnitude of change, longevity and composition of any increase in understory vegetation is unknown. We sampled locations on the George Washington and Jefferson National Forests that had received CTR treatments over the past ten years (between 2014 and 2024). Understory data were collected within one-meter square sampling areas near released and non-released trees to determine woody plant species abundance and composition. Crown widths, diameter at breast height, crown height and total height of crop trees were measured, and epicormic branching was ranked. Understory vegetation was dominated by five species: teaberry (Gaultheria procumbens), greenbrier species (Smilax spp.), red maple (Acer rubrum), eastern white pine (Pinus strobus), and blueberry species (Vaccinium spp.). We found that at two, three, five, and seven years post-release there was a significantly more understory stems surrounding released trees compared to non-released trees. Moreover, we found species richness to be greater around release trees one, five, and seven-years post-release, while species diversity was only greater around released trees one-year post-release. We also found that the crowns of released trees were significantly wider than that of non-released trees and that epicormic branching did not differ between released and non-released trees.