Evaluation of cleanings to maintain oak forests on the Allegheny National Forest

Abstract

Ten-year results for an administrative study on the Allegheny National Forest (ANF) that examined their cleaning (precommercial thinning) prescriptions and standards for success in maintaining oak (Quercus spp.) composition in young stands and maintaining oak stems in a competitive position are presented. Two studies were installed. One study was in a 25- to 30-year-old stand where we released intermediate and suppressed oak species, in particular white oak (Quercus alba), to see if they would survive and improve in crown class. The other study was installed in two 16-year-old stands where cleanings using crown-touching crop-tree release treatments were done, with untreated control plots reserved. A total of eight treated and eight control plots in two stands were examined. In the first study, mortality of white oaks in the lower canopy (intermediate or overtopped) was 83 and 39% in control versus treated areas, respectively. The cleaning treatments were successful in keeping trees alive, but crown vigor declined and no trees increased in crown class. In the second study, the mortality of crop trees was 15 and 2% in control versus treated stands, respectively. The proportion (number of stems) of crop trees of all species in the upper canopy (dominant or codominant) dropped 22% versus 1% for control versus treated trees over the 10 years. Stand-level oak composition in control stands was 11.3% of basal area after 10 years (11.7% initially). In treated stands, it was 18.3% of basal area after 10 years (10.7% initially), a 71% increase in oak. The treatments successfully increased survival, growth, and composition of oak.