M. Reichstein et al., Temperature dependence of carbon mineralisation: conclusions from a long-term incubation of subalpine soil samples, SOIL BIOL B, 32(7), 2000, pp. 947-958
Carbon mineralisation from soil samples was analysed during a 104-day labor
atory incubation at 5, 15 and 25 degrees C. The samples were taken from the
upper horizon of each of two topographically different micro-sites (gully:
A-horizon; ridge: Oe/Oa-layer) at the Stillberg Alp close to Davos in the
Swiss Central Alps. On both the soils, carbon mineralisation rates decrease
d substantially with incubation time (e.g. from 0.3 to 0.18 mg CO2-C d(-1)
g(-1) organic carbon in the Oe-Oa-layer and from 0.6 to 0.2 mg CO2-C d(-1)
g(-1) organic carbon at 25 degrees C in the A-horizon). Carbon mineralisati
on was well described by a first-order kinetic two-compartment model and a
functional temperature dependence of the rate constants. Both temperature m
odels, the exponential pro-function and a quadratic function described the
cumulative C-mineralisation correctly within one standard error of estimate
(SE) of the measured values. However, the Q(10) model gave a slightly bett
er fit to the data, and Q(10)-values of 2.5 and 2.8 were computed for the r
ate constants of the organic layer and the A-horizon, respectively. While t
he temperature dependence of the (time independent) rate constants of miner
alisation appeared to be well-defined, this was not the case for Q(10) of t
he instantaneous respiration rates, which were a non-linear function of inc
ubation time. The general pattern of fluctuation of the instantaneous Q(10)
-values was in accordance with the results computed by the models, and can
be explained by the parallel decomposition of two different soil organic ma
tter pools. To avoid the effects of the time of the respiration measurement
on the calculated Q(10), it is recommended to analyse the whole time serie
s in order to infer the temperature dependence of respiration, or at least
to standardise the time at which soil respiration is measured. In a second
part of the study, our laboratory results temperature effects were extrapol
ated to the field, using measurements of soil temperature as driving variab
les to a recently developed carbon balance model. Carbon mineralisation was
roughly estimated to be 52-84 g C m(-2) year(-1) for the gullies and 70-12
5 g C m(-2) year(-1) for the ridges. Unexpectedly, the choice of the temper
ature model had a great influence on the estimate of annual carbon minerali
sation, even though models differed only little concerning the fit to the l
aboratory incubation data. However, it could be shown that winter-time mine
ralisation probably accounted for at least 22 and 40% of the whole-year min
eralisation on the ridges and the gullies, respectively, and therefore, sho
uld not be neglected in carbon-balance studies. (C) 2000 Elsevier Science L
td. All rights reserved.