The carbon budget of coarse woody debris in a temperate broad-leaved secondary forest in Japan.

We evaluated the carbon budget of coarse woody debris (CWD) in a temperate broad-leaved secondary forest. On the basis of a field survey conducted in 2003, the mass of CWD was estimated at 9.30 tC ha⁻¹, with snags amounting to 60% of the total mass. Mean annual CWD input mass was estimated to be 0.61 tC ha⁻¹ yr⁻¹ by monitoring tree mortality in the forest from 1999 to 2004. We evaluated the CWD decomposition rate as the CO₂ evolution rate from CWD by measuring CO₂ emissions from 91 CWD samples ( R_CWD) with a closed dynamic chamber and infrared gas analysis system. The relationships between R_CWD and temperature in the chamber, water content of the CWD, and other CWD characteristics were determined. By scaling the measured R_CWD to the ecosystem, we estimated that the annual R_CWD in the forest in 2003 was 0.50 tC ha⁻¹ yr⁻¹ or 10%–16% of the total heterotrophic respiration. Therefore, 0.11 tC ha⁻¹ yr⁻¹ or 7% of the forest net ecosystem production was sequestered by CWD. In a young forest, in which CWD input and decomposition are not balanced, the CWD carbon budget needs to be quantified for accurate evaluation of the forest carbon cycle and NEP. [ABSTRACT FROM AUTHOR]