Factors affecting self-pruning in Northern Red Oak : (Quercus rubra L.) /

by Jenniges, Stephanie M.

Northern red oak (Quercus rubra L) is an important timber species in the United States, and especially in Wisconsin, where the 1996 growing stock was over 2.7 billion cubic feet. Northern red oak is the highest valued timber in Wisconsin. Defects in stem quality lower timber value, but thinning and pruning regimes can be used to reduce these defects, at a cost. Northern red oak is a self-pruning species, and this characteristic may be used to reduce the cost of producing high-quality wood. The objectives of the study were to 1) determine how forest stand density affects tree characteristics and self-pruning in northern red oak, and 2) to recommend practices, which incorporate the regulation of stand density, to encourage self-pruning in northern red oak. Fifty trees were sampled from ten stands in northern and central Wisconsin. Data collected included stand density and density around the sample trees, dbh, total height, height, length, and diameter of the lowest living and dead branches, and crown area. Predictive models were developed to describe the tree characteristics. BA/acre was found to be a significant variable in the models for percent clear bole and rate of crown recession (two descriptors of self-pruning), but the models themselves were not good predictors. A secondary study included in this research sought to determine the genetic make-up of the sample trees. Northern red oak and northern pin oak (Quercus ellipsoidalis) hybridize in the wild and both are located in Wisconsin. Northern pin oak is not a self-pruning species. Past studies have been unable to find a strong method for determining if a tree is a northern red iii oak, a northern pin oak, or a hybrid of the two. For the purposes of the study, true northern red oak were required. The secondary study used RAPDs (Random Amplified Polymorphic DNA) in an attempt to first find a genetic marker to distinguish between the two species and then to determine if the sample trees were true northern red oak. Several primers were tested. The genetic study was inconclusive and more research is needed to find a distinct northern red oak genetic marker. iv