Evaluating elevated levels of crown dieback among northern white-cedar (Thuja occidentalis L.) trees in Maine and Michigan: a summary of evaluation monitoringThis article is part of a larger document. View the larger document here.
Analysis of crown condition data for the 2006 national technical report of the Forest Health Monitoring (FHM) Program of the Forest Service, U.S. Department of Agriculture, exposed clusters of phase 3 plots (by the Forest Inventory and Analysis [FIA] Program of the Forest Service) with northern white-cedar (Thuja occidentalis L.) crown dieback averages of 10 percent or more in Maine and northern Michigan (Randolph 2009). Such elevated levels of dieback were of concern because unlike hardwood trees, conifers often do not exhibit crown dieback unless the tree, and in particular its root system, is under serious stress (Millers and others 1992). An examination of the plots with elevated dieback showed that the high dieback averages for northern whitecedar (NWC) were not necessarily accompanied by elevated average dieback levels among the other tree species on the same plots. Plot-level condition and disturbance information, the NWC literature, and local experts were consulted to ascertain potential causes of the elevated levels of crown dieback. When no specific causes were evident, we initiated an Evaluation Monitoring (EM) project in order to verify the apparently elevated levels of crown dieback (Randolph 2008).