Crown Class Dynamics of Oaks after Commercial Thinning in West Virginia: 30-Year Results

by

Gary W. Miller, Jamie L. Schuler, and James S. Rentch

Research Forester (GWM), USDA Forest Service, Northern Research Station, 180 Canfield Street, Morgantown, WV 26505; Assistant Professor (JLS) and Research Assistant Professor (JSR), Division of Forestry and Natural Resources, West Virginia University, Morgantown, WV. GWM is corresponding author: to contact, call 304-285-1521 or email at gwmiller@fs.fed.us.

Abstract – Commercial thinning in hardwood stands is generally applied to reduce overcrowding and to favor the development of desired residual species until the stand is mature. In mixed hardwood stands, commercial thinning also provides an opportunity to promote vigorous overstory oaks (Quercus spp.) that will serve as sources of acorns and advanced seedlings needed to regenerate oaks in the next stand. Forest managers need information on sustaining and increasing the number of overstory oaks at mid-rotation, when the stand is still several decades from maturity. In this study, crown class dynamics of 897 northern red, chestnut, and scarlet oaks were monitored for 30 years after commercial thinning in 53-year-old central Appalachian mixed hardwoods. Twenty 3-acre treatment plots were included in the study, and individual trees were examined immediately after thinning in 1983 and again in 2013. Fisher’s exact test was used to compare the distributions of ending canopy position for thinned and control plots. In general, thinning enhanced crown class stability and survival rates of oaks that began in the upper canopy. For oaks that began in the intermediate crown class, the transition rates to the upper canopy after thinning were 33, 25, and 0 percent for northern red oak, chestnut oak, and scarlet oak, respectively. In control plots, oaks that began in the lower canopy had greater mortality rates and very few trees ascended to the upper canopy. Forest managers can use this information to plan mid-rotation thinning treatments to enhance upper canopy species composition in the latter stages of stand development.