Crown Class Transition Rates of Maturing Northern Red Oak (Quercus rubra L.)

Abstract

Crown classes and diameters of 704 northern red oaks on medium quality sites were measured at 10-yr intervals between 1927-1987. Nominal age of northern red oaks at the beginning of the study was 25 yr. Mortality rates between ages 25-55 and between ages 55-85 decreased with each increase in crown class (i.e., mortality of dominant is < codominant is < intermediate is < suppressed). Ascension rates into higher crown classes increased with each increase in crown class between ages 25-55 and between ages 55-85. Mortality rates of dominant, codominant, and intermediate trees were higher between ages 55-85 than between ages 25-55. The cause of the increased mortality was likely periodic episodes of defoliation which began after age 55. Within several diameter classes at age 25, survival through age 55 and the proportion found in upper canopy at age 55 increased with crown class. Mortality rates between ages 25-55 were lower for the largest northern red oak in a sprout clump than for lesser sprouts and for those trees which were not part of a sprout clump. There was no significant difference in canopy position transition rates between ages 55-85 for the largest red oaks in a sprout clump and those trees which were not part of a sprout clump. However, mortality rates between ages 55-85 of lesser trees in a sprout clump were significantly higher than for either the largest sprout in a clump or for those trees which were not part of a sprout clump. Survival of suppressed and intermediate 25-yr-old red oak was negatively related to the number of oaks in dominant and codominant crown classes. Crown class can be a powerful tool for determining the future status of maturing northern red oaks in southern New England. For. Sci. 40(2): 221-237.