| Previous theoretical analyses based on Arrhenius kinetics and thermodynamics have shown
that the temperature sensitivity of low-quality substrate is higher than that of high-quality
substrate. Because soils store large amounts of low-quality carbon, understanding its response
to increasing temperatures will help to predict the response of atmospheric CO2 to climate
change. However, the empirical evidence available does not provide conclusive evidence to
corroborate this theoretical argument. Although there are various possible reasons for this
disagreement, the theory behind this argument has not been scrutinized carefully. Based on a
simple mathematical analysis it is shown in this study that low-quality substrates
are less temperature sensitive when analyzed in absolute rather than in relative
terms, a result that may seem counterintuitive to previous theory. However, this
is a paradox intrinsic to the Arrhenius equation and it is often ignored within the
‘quality-temperature’ debate. In fact, different measures commonly used to analyze the
temperature sensitivity of different substrates can provide apparently different and
contradictory results even though they are based on the same basic principles. Distinguishing
between absolute and relative measures of sensitivity is essential for understanding the
sensitivity of respiration to environmental change. An analysis of the available
empirical evidence on this topic shows that most studies actually agree with the
Arrhenius and thermodynamics theory, with less disagreement than previously
thought. |