Accumulation and decay of woody detritus in a humid subtropical secondary pine forest

The contribution of coarse woody detritus (CWD) to forest C budgets is poorly quantified in general, and especially so for secondary forests. This study quantifies C and N storage in logs and snags and compares the decomposition of this aboveground CWD with that of dead taproots in a 50-year-old secondary pine forest in a humid subtropical climate. We estimated rates of CWD input due to tree mortality over 50 years of forest development and conducted a field inventory of aboveground CWD of four decay classes. Belowground CWD was characterized by excavating 13 taproots of three decay classes. We found that aboveground CWD in this warm and humid climate decays relatively rapidly, with an exponential decay constant of 0.122 and mean time to decomposition of 50% and 95% log mass of 5.6 and 24.3 years, respectively. Our data suggest that most dead trees proceed through the earliest stage of decomposition as standing snags before falling to the ground. We found that changes in wood chemistry during decomposition were similar above and below ground. After 50 years of forest development, logs, snags, and dead taproots comprised 13% of total forest ecosystem C in this secondary pine forest.