Soil carbon and coarse woody debris pools across a clearcut and burned chronosequence.

Abstract

The size of both the CWD and soil C pools can drive the net ecosystem productivity (NEP) of a forest, losing C to the atmosphere through heterotrophic respiration and accruing C when the inputs have increased. Disturbance needs to be taken into account when modeling C storage. We estimated the mass of soil carbon (C) and coarse woody debris (CWD) C pools in clearcut and burned chronosequence stands (7-, 25-, 51-, and 69-yrs-old) in northern lower Michigan. The CWD-C mass in the 7-yr-old stand (8.40 +- 0.90 Mg C/ha) was signficantly greater than the four older stands (p<0.05), which were not significantly different from each other. The temporal pattern of CWD-C mass generally to follow the U-shaped pattern observed in other studies. We sampled mineral soil C pool at three depths (0-20, 20-40, 40-80 cm). The temporal patterns of the three depths were signficantly different, with the top (0-20 cm) layer exhibiting a U-shape distribution of C over time and the lower two (20-40 and 40-80 cm)not differing across stand age. The 7-yr-old stand had signficantly more C in the 0-20 cm layer of soil than the reference stand (11.95 +-0.87 and 6.47 +- 0.38 Mg C/ha, respectively). These results suggest that disturbance has a large effect on both pools through the input of legacy C.