EPICORMIC BRANCHING OF CALIFORNIA BLACK OAK - EFFECT OF STAND AND TREE CHARACTERISTICS

Young California black oak (Quercus kelloggii Newb.) stands usually re quire thinning to increase production of acorns and wood products, but epicormic branches, which yield no acorns and constitute a serious lu mber degrade. often result. A crown thinning in 60-year-old hardwood s tands on a south exposure at the Challenge Experimental Forest in the northern Sierra Nevada of California created basal areas that ranged f rom 20 to 35 m2 per ha. Trees in a control and bordering small opening s expanded the basal area range. In 1976 or 6 to 9 years after thinnin g, 2069 living and dead epicormic branches on 189 California black oak trees were observed. Statistically significant (alpha = 0.05) predict ors of epicormic branching were position in stand, cardinal direction of bole face, and bole segment-variables that generally affected epico rmic branching on eastern species of deciduous oaks. Number of epicorm ic branches increased with decreasing stand density, proximity to open ings, on south and east bole faces. and with increasing distance above the stump. These findings, together with silvicultural recommendation s for enhancing crown development and lessening epicormic branching of California black oak, are discussed.