Tree bark represents an important but rather poorly investigated component of coarse woody debris (CWD). We applied the component integration method to partition CO₂ flux from the surface of CWD into tree bark respiration and exposed wood surface respiration. Twelve large fragments of spruce (Picea abies (L). Karst), birch (Betula pubescens Ehrh and B. pendula Roth), and aspen (Populus tremula L.) logs at various times since tree death (TTD) were collected in middle taiga old-growth forest and transported to the laboratory. CO₂ fluxes were measured by a closed chamber method using a portable infrared gas analyser. During the first hours after the removal of bark from the logs, we observed a pronounced increase in CO₂ fluxes (i.e. a respiration burst) from the exposed wood surface and cutaway bark. The TTD had an important influence on the time required for stabilization of CO₂ emission rates from the tree bark and exposed wood surface. The mean rate of CO₂ flux from undisturbed surfaces of log fragments (R_{log surface}) varied from 23 ± 1 to 45 ± 2 mg С m^-2 h^-1, depending on the TTD. The bark respiration rate was significantly lower than the respiration rate of exposed wood. Tree bark of fresh logs (i.e. 0–1 y TTD) contributed a larger portion (40%) to the total CO₂ flux from CWD than tree bark of slightly and moderately decayed logs (15–16%). We suggest using this methodological approach for partitioning CO₂ fluxes from fresh and moderately decomposed CWD in both field and laboratory studies.

Keywords: deadwood; middle taiga; decay, carbon, tree bark, wood, respiration.