Partitioning of CO2 Fluxes from Coarse Woody Debris: Adaptation of the Component Integration Method

Abstract

Tree bark represents an important but the most poorly investigated component of coarse woody debris (CWD). We applied the ‘component integration method’ to partition the CO₂ flux from CWD surface into the respiration of tree bark and exposed wood surface. Twelve large fragments of spruce, birch, and aspen logs of various times since tree death (TTD) were collected in the middle taiga old-growth forest and transported to the laboratory. The CO₂ fluxes were measured by a closed chamber method using a portable infrared gas analyzer.

Throughout the first hours after the removal of bark from logs, we observed a pronounced increase of CO₂ fluxes, or ‘respiration burst’ from the exposed wood surface and cutaway bark. The longest time periods required for the stabilization of the CO₂ flux from birch wood belonging to 0–8 years of TTD (3.33 h). The spruce bark of TTD of 10 years demonstrated the shortest stabilization time (0.17 h). The mean rate of CO₂ fluxes from an undisturbed surface of log fragments was 30.9 mg С m^–2 h^–1. Bark respiration rate was in most cases lower than the respiration rate of exposed wood. Bark contribution to the total CO₂ flux from the log surface varied between 6 and 50% depending on log species identity and TTD. We suggest using this methodological approach for partitioning CO₂ fluxes from CWD of 1–3 decay class in both field and laboratory studies.

Keywords: deadwood; middle taiga; decay; carbon; tree bark; respiration