- Hofmeyer, Philip V.
University of Maine Graduate School
Northern white-cedar (Thuja occidentalis L.) management has been hindered throughout is native range in part because of a lack of fundamental ecology and silviculture research. Efforts to tend and regenerate northern white-cedar stands fi'equently yield inconsistent and unpredictable results due to disagreement regarding of its ecology. In the present study, two breast-height cores were extracted from 625 outwardly sound sample trees at 60 sites in northern Maine. Northern white-cedar annual basal area growth predicted from breast height sapwood area was compared to that red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) along site class and light exposure gradients. A subsample of 25 sound northern white-cedar trees was stem analyzed to develop allometric leaf area equations and test for differences in growth efficiency by site and light exposure. An additional 59 sound northern white-cedar trees were stem-analyzed to reconstruct early height and diameter development. Results suggest that northern white-cedar growth is not strongly affected by site class or light exposure class. Central decay from heart rot fungi occurred in nearly 80% of the northern white-cedar trees sampled. Incidence of decay and proportion of basal area centrally decayed increased as soil drainage improved. Projected leaf area and crown foliage mass were estimated with a nonlinear basal area and live crown ratio model. Volume increment per unit leaf area was modeled with a two-parameter nonlinear power function. Growth efficiency was not strongly influenced by site class, canopy position, breast height age, or presence of central decay. Early stem data suggest that many of the sound cedar trees sampled had a history as advance regeneration. Early height and diameter growth were slow, though most trees had a period of release in their ring chronology coinciding with known spruce budworm (Choristoneura fumiferana) epidemics. Managers are recommended to favor individuals with large crowns as residuals in partial harvests regardless of site class. Northern white-cedar could likely be managed successfully with uneven-aged silviculture or variants of the shelterwood system. Caution should be taken to avoid residual stand damage to seedlings and saplings during harvesting operations.