The dependence of soil CO2 efflux on temperature

Assessing the global C budget requires a better understanding of the effect of temperature on soil CO2 efflux both from experiments and developments in theory. Intact soil cores (ca. 31 cm in diameter and 45 cm in depth) were collected from a farmland and a sitka spruce site near Edinburgh, Scotland, and incubated in a growth chamber with varying temperature and soil moisture contents. There was no influence of incubation time on the measured soil respiration rate found in this study and this is different from previous studies that commonly use a re-constructed soil sample. Both soils showed an exponential increase in respiration rate with temperature. No optimal temperature for soil respiration was found with soil temperature up to 32°C. The influence of soil moisture content, varying between 20 and 50 vol%, on soil respiration and its response to temperature was not obvious. Most equations describing the relationship between soil respiration and temperature fitted the observed data well. However, based on model and Q10 analysis, the Arrhenius model may be better than the others in its performance and theoretical basis, despite a tendency to underestimate somewhat the response of soil respiration at low temperature. A simple empirical equation, Rs=a(T−Tmin)b, is presented, which is more responsive at low temperature than the Arrhenius and exponential models.