Kirschbaum, M.U.F. (2004).
Soil respiration under prolonged soil warming: are rate reductions caused by
acclimation or substrate loss? Global Change Biology 10: 1870-1877.
The world’s soils
contain a large amount of carbon so that even a fractionally small loss or gain
could have a quantitatively important feedback-effect on net CO2
emissions to the atmosphere. It is therefore important to fully understand the
temperature dependence of soil carbon decomposition. Evidence from various
observations can be used to quantify the temperature dependence of carbon
efflux, but it is important to ensure that confounding factors, such as
changing water relations or availability of readily decomposable substrate, are
fully considered in inferring an underlying temperature response from observed
response patterns.
A number of recent
findings from soil-warming experiments have led to the suggestion that
stimulation of soil carbon efflux by increasing temperature is only transitory
before acclimation takes place and carbon efflux rates return to similar rates
as before the increase in temperature. It is shown here that this response
pattern can be explained through a simple two-pool soil-carbon model with no
acclimation response needing to be invoked. The temporal pattern is instead due
to depletion of readily decomposable substrate. It shows that findings of
reduced respiration rate in soil-warming experiments are consistent with
unchanged high temperature sensitivity of organic carbon decomposition and
affirms that there is, indeed, a danger of positive feedback between global
warming and the release of soil organic carbon that can lead to further
warming.