Dynamics of temperature normalized stem CO2 efflux in Norway spruce stand

Abstract

Respiration of stems contributes approximately 8 to 13 % to the total respiration of forest ecosystem, which is not negligible, and it has to be included in carbon flux estimates. The aim of this study was to determine dynamics of stem CO2 efflux during the growing season in Norway spruce stand and factors affecting this efflux. Continuous measurements of stem CO2 efflux were carried out by an automated system during the growing season in 2006–2009. Further measured characteristics were stem temperature, stem increment and precipitations. Stem CO2 efflux was in tight relationship with changes in temperature with the mean coefficient of determination of 0.76. This infers that temperature was the main factor driving changes in CO2 efflux during the season. To eliminate effect of temperature and determine other factors influencing stem CO2 efflux, CO2 efflux was normalized for temperature of 10 °C (R10). Basic seasonal course of R10 followed the pattern of stem growth rate with its maxima in June and July. The other factor effect, which was possible to determine, was presence of rainfall. Rainfall strong enough caused mostly increase in R10. This effect was the most significant when the R10 course had a decreasing trend in the second part of the growing season.

Keywords

• soil CO₂ efflux
• R₁₀
• <i>Picea abies</i>
• precipitations
• stem growth