Northern White-Cedar Regeneration Dynamics on the Penobscot Experimental Forest in Maine: 40-Year Results

Abstract

Abstract The objective of this study was to assess the long-term dynamics of northern white-cedar (Thuja occidentalis L.) seedling and sapling growth and mortality on the Penobscot Experimental Forest in Maine. Data collected between 1965 and 2005 in four twice-replicated partial cutting treatments were analyzed. White-cedar seedlings established in all treatments despite relatively high white tailed-deer (Odocoileus virginianus Zimmerman) population densities. However, although it appears that regeneration cohorts of associated softwoods increased in size over time, the white-cedar cohort did not. Ingrowth of white-cedar from the seedling to sapling stage was lower than the combined rates of sapling mortality and recruitment to the pole stage; sapling density of this species in 2005 was >80% less than it was at the start of the measurement period. Sapling mortality was high, and recruitment to larger size classes was low, although mortality decreased and recruitment increased as sapling size increased. Browsing was prolific; 90% of white-cedar seedlings and small saplings showed signs of browse in 2005. Overall, white-cedar sapling growth was slow, with an estimated 100 years needed to grow from small sapling to merchantable size in the study stands. Efforts to release white-cedar saplings through precommercial treatment and control of browsing pressure are recommended.