Applications of Growth and Survival Equations for Oregon White Oak in the Pacific Northwest

Urban and agricultural development has greatly reduced the area of Oregon white oak (Quercus garryana; also known as Garry oak) woodlands and savannas in the Pacific Northwest, and much of the remainder is succeeding, or has already succeeded, to coniferdominated forests. Conifer encroachment and, in some cases, the development of dense oak stands present significant management challenges. In this paper, new equations, now available in ORGANON, are used to predict oak growth and survival with and without management in three stands: a single-storied conifer-oak stand, a two-storied conifer-oak stand where conifers were overtopping the oaks, and a dense pure oak stand. Without conifer removal, oak basal area was projected to decline in the single-storied stand and oak mortality was projected to accelerate. Very high oak mortality (90 percent over the 50-yr projection period) was projected in the two-storied stand. Conifer removal was projected to greatly reduce mortality and increase the diameter growth of oaks in both stands. Thinning in the pure oak stand was projected to nearly triple the average diameter growth of surviving trees. The three examples indicate that management can have a dramatic effect on Oregon white oaks under stand conditions that are now common throughout the species’ range.