General Ecology–Structure — Abstract of Paper


Coast Live Oak Long-term Thinning Study—Twelve-Year Results
Norman H. Pillsbury,¹ Lawrence E. Bonner,² and Richard P. Thompson¹


Age structure and growth of California black oak (Quercus kelloggii) was determined from tagged trees at four 26.1-acre study stands in Placer County, California. Stands were dominated by large diameter (>20 inch dbh) California black oak and ponderosa pine (Pinus ponderosa). Randomly selected trees were tagged in June-August 1998 and harvested under a group selection timber harvest in October-November 1998 and May-June 1999. Trees averaged 148 years of age (range = 58 to 356 years, n = 108), and ages differed among the four stands (P < 0.006). Stands had uneven distributions of tree ages, diameters, and heights. A nonlinear regression model was developed that predicted tree age based on diameter (R² = 0.74). The average 10-year increment of radial growth was 0.72 inches (range = 0.14-2.26 inches, n = 122), and radial growth decreased as basal area increased (nonlinear regression, R² = 0.34). If average growth rates are desired, basal area retention should average around 100-115 ft²/acre and 200-225 ft²/acre for California black oak and all trees, respectively, for stands in the central Sierra Nevada with attributes that are similar to our study stands.