Structure of Quercus gambelii communities in the Lincoln National Forest, New Mexico, USA

Abstract

The structure of eight Quercus gambelii (Gambel's oak) communities in the Lincoln National Forest, New Mexico, USA were examined. Belt transects were used to estimate the density and basal area of the trees and the density of juvenile woody plants. In addition, diameter size-class distributions of Q. gambelii were examined to determine community development. The communities were estimated to be 109–137 years old and mid to late-successional. Total tree density was 3586–6480 plants/ha, with Q. gambelii having a relative density of 94–100%. Total basal area was 20.1–42.0 m 2/ha, with Q. gambelii relative basal area 82–100%. The density and basal area of all other species present was low. Quercus gambelii juvenile density ranged from 1760 to 9160 plants/ha. Juveniles of all other species found were zero to 847 plants/ha. Based on Weibull analyses, all of the diameter size-class distributions of Q. gambelii were unimodal. There were few or no individuals in the smallest (1–5 cm) diameter size-classes, suggesting that recruitment of small Q. gambelii plants into the adult population may be below the replacement rate for these stands. Pooled size-class distributions for the other species were non-normal with most individuals in the smallest diameter size-classes. Low light levels below the canopy, a lack of canopy gaps, or browsing by Cervus elaphus (elk = red deer) may be the primary causes of poor recruitment because there were large numbers of Q. gambelii juveniles, but these individuals are not entering the small-tree size-class in any of the communities.