Temperature and moisture effects on respiration rate of decomposing logs in a Sitka spruce plantation in Ireland.

摘要

In this study, a dynamic chamber method was used to measure respiration rates ( RCWD) of logs in five decay classes (DCs) (ranging from freshly felled logs in DC 0 to highly decomposed logs in DC 4) in a Sitka spruce ( Picea sitchensis (Bong) Carr.) forest stand. The effects of change in temperature ( Tc) and log moisture content (MC t) on RCWD were determined and annual decay rates estimated. The decay rates were used to estimate annual carbon (C) flux from logs resident in six managed Sitka spruce forest stands of different ages (23-45 years). The highest mean RCWD was recorded for DC 3 logs (40.43 mg CO 2 kg -1 h -1) and the lowest for freshly felled DC 0 logs (10.16 mg CO 2 kg -1 h -1). Tc accounted for 62-85 per cent of the variation in RCWD from logs in different DCs, whereas MC t accounted for 0.07-74 per cent. Together, Tc and MC t accounted for 78-87 per cent of the variation in RCWD. Decay rates for all DCs ranged from 0.007 to 0.063 year -1, and the C flux ranged from 0.011 to 0.504 Mg C ha -1 year -1 and was not dependent on forest age or the number of thinnings. Knowledge of the contribution of coarse woody debris (CWD) fluxes to total forest ecosystem respiration will improve the accuracy of forest C accounting and assist in CWD management.