ON THE TEMPERATURE-DEPENDENCE OF SOIL RESPIRATION

1. From previously published measurements of soil respiration rate (R) and temperature (T) the goodness of fit of various R vs T relationships was evaluated. 2. Exponential (Q10) and conventional Arrhenius relationships between T and R cannot provide an unbiased estimate of respiration rate. Nor is a simple linear relationship appropriate. 3. The relationship between R and T can, however, be accurately represented by an Arrhenius type equation where the effective activation energy for respiration varies inversely with temperature. An empirical equation is presented which yields an unbiased estimator of respiration rates over a wide range of temperatures. 4. When combined with seasonal estimates of Gross Primary Productivity (GPP) the empirical relationship derived provides representative estimates of the seasonal cycle of net ecosystem productivity and its effects on atmospheric CO2. The predicted seasonal cycle of net ecosystem productivity is very sensitive to the assumed respiration vs temperature relationship. 5. For biomes in areas where soil temperatures are low, soil respiration rate is relatively more sensitive to fluctuations in temperature. Nevertheless, more information is required before any predictions can be made about changes in soil carbon pools in response to future temperature changes.