Effects of Timber Stand Improvement Treatments on Tree Growth in Southwestern Virginia

Non-industrial private forestlands (NIPF) have often been subjected to logging practices that remove the highest quality trees of the highest value species, leaving behind less-desirable stems and species; a practice termed high-grading or selective harvesting. Timber stand improvement (TSI) can be used to correct high-grading practices by removing poorly-formed or low-value tree species in order to promote the growth of higher value trees and species. The felled trees may be removed for biomass fuel or left in place. At study sites in southwestern Virginia, we monitored tree growth across experimental TSI with biomass removal, TSI cut-and-leave felled stems, and control plots in mixed-pine hardwood forests from 2012–2025, measuring diameter at breast height (DBH) for multiple species. Scarlet Oak (Quercus coccinea) and Yellow Poplar (Liriodendron tulipifera) had the largest growth increments during the study period, while Black Gum (Nyssa sylvatica) and Hickory species (Carya spp.) showed consistently low growth. Larger trees tended to grow at faster rates, consistent with allometric expectations. The two TSI treatments had similar growth increments and were 60%–100% higher than control plots over the tree blocks of treatments in this study. Mortality at the longest-term measured block was more than twice as high as TSI plots. These results suggest that TSI can reduce competition for light and nutrients promoting diameter growth, whereas untreated plots may experience resource limitations that suppress growth and increase mortality. The study provides a baseline for understanding forest dynamics and highlights the importance of management interventions in maintaining productivity and structural diversity in selectively-logged forests.