Determining year of death of logs and snags of Thuja plicata in southwestern coastal British Columbia

The years of death of Thuja plicata (Donn ex D. Don in Lamb.) logs and snags from cool mesothermal forests of southwestern coastal British Columbia are reported. We sampled 15 logs in decay classes I(recent) to IV (old) and 17 snags in decay classes III (recent) to VI (old). Stages of decay were determined from the physical structure of each bole using published methods. Decay class IV logs, aged by radiocarbon dating, were from trees that died approximately 550-1200 years ago. Year of death of class I, II, and III logs and all snags was obtained by dendrochronological techniques. Crossdating of increment cores indicated that the trees from which they came died 1-279 years ago for logs and 2-276 years ago for snags. Crossdating results were compared with dates of scars, reaction wood, and releases of neighbouring trees and with the ages of seedlings and saplings growing on logs. These indirect methods could not be relied on to estimate the time of tree death, based on the crossdating estimates. There were no statistically significant differences in the times of tree death for class II and III logs or for class IV, V, and VI snags. Although Thuja plicata logs and snags can be placed into different decay classes based on physical appearance, only a four-class decay classification appears appropriate for logs, and no classification system appears appropriate for snags, based on times of tree death. Snags may remain standing for over 270 years.