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 i n 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 moist ure contents. There was no influence of incubation time on the measured soi l respiration rate found in this study and this is different from previous studies that commonly use a reconstructed soil sample. Both soils showed an exponential increase in respiration rate with temperature. No optimal temp erature for soil respiration was found with soil temperature up to 32 degre esC. 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 tempera ture fitted the observed data well. However, based on model and Q(10) analy sis, the Arrhenius model may be better than the others in its performance a nd theoretical basis, despite a tendency to underestimate somewhat the resp onse of soil respiration at low temperature. A simple empirical equation, R -s = a(T - T-min)(b), is presented, which is more responsive at low tempera ture than the Arrhenius and exponential models. (C) 2001 Elsevier Science L td. All rights reserved.