Tipping the carbon balance? Woody debris production and respiration following moderate disturbance.

Abstract

Coarse woody debris (CWD) is a significant and growing component in forest ecosystems, especially those undergoing succession or withstanding disturbances. We combined CWD census data and in situ chamber respiration measurement to quantify the amount and carbon stored by CWD in an experimentally disturbed early successional aspen and birch forest. CWD was found to be 35.2 Mg C ha-1 of which was 29.3 Mg C ha-1 standing and 5.9 Mg C ha-1 was downed. Downed CWD respiration averaged 1.1 μm CO2 kg-1 s-1, but significant differences were found based on orientation, side or end. A statistical multi-variate linear combination model that related orientation, decay class, and CWD temperature to instantaneous efflux was used to model ecosystem level respiration for the month of July 2013. Total respiration was found to be 276.9 ± 223.1 kg C ha-1 mo-1. When compared to net ecosystem productivity and pre-disturbance CWD respiration rates, the our July 2013 respiration total represents a significant increase in respiration rates with the potential to limit the forest’s ability to act as an effective carbon sink in the future.