Dynamics of dead wood over 20 years in a New England oak forest

Trees and snags with diameter at breast height (dbh)=>5 cm were measured in 1983, 1993, and 2003 on 117 plots, each having an area of 200-m^2, in an 80year-old forest in western Massachusetts. In 2003 we measured dead stumps and coarse woody debris (CWD) with diameter =>10 cm using the line intercept method. Decadal mortality rates were 9.4% and 9.0% per decade (7.1 and 5.0 m^3.ha^-1, respectively). Mortality rates were highest (32%) in low-vigor suppressed trees. Snags with dbh > 10 cm occurred on 72% and 62% of plots, respectively, in 1983 and 2003. Snag volume decreased from 13.2 to 8.7 m^3.ha^-1 over the 20-year period. From 1983 to 2003, 88% of a cohort of oak (Quercus spp.) snags, probably killed by gypsy moths (Lymantria dispar L.), had fallen. Decadal fall rates of snags averaged 61% and 66% (6.8 and 4.5 m^3.ha^-1, respectively). CWD logs were measured on 55% of plots and averaged 10.1 m^3.ha^-1. Stumps were on 62% of plots and averaged 0.7 m^3.ha^-1. Seventy percent of stumps, but only 38% of logs, were in the two most decayed classes. Trees cut the previous decade contributed 6% of CWD logs measured. Few snags were cut (1.6 and 0.4 m3·ha-1, respectively, in 1983-1993 and 1993-2003). Snag production and fall rates were higher than in other forests, but CWD volume was lower.