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| Couteaux, MM; Bottner, P; Anderson, JM; Berg, B; Bolger, T; Casals, P; Romanya, J; Thiery, JM; Vallejo, RV: Decomposition of 13C-labelled standard plant material in a latitudinal transect of European coniferous forests: Differential impact of climate on the decomposition of soil organic matter compartments, Biogeochemistry, 54, 147-170 (2001) | |
Abstract:
13C labelled plant material was incubated in situ over 2 to 3 years in 8 conifer forest
soils located on acid and limestone parent material along a north-south climatic transect from
boreal to dry Mediterranean regions in western Europe. The objectives of the experiment were
to evaluate the effects of climate and the soil environment on decomposition and soil organic
matter dynamics. Changes in climate were simulated using a north-to-south cascade procedure
involving the relocation of labelled soil columns to the next warmer site along the transect.
Double exponential, decay-rate functions (for labile and recalcitrant SOM compartments)
vs time showed that the thermosensitivity of microbial processes depended on the latitude from
which the soil was translocated. Cumulative response functions for air temperature, and for
combined temperature and moisture were used as independent variables in first order kinetic
models fitted to the decomposition data. In the situations where climatic response functions
explained most of the variations in decomposition rates when the soils were translocated, the
climate optimised decomposition rates for the local and the translocated soil should be similar.
Differences between these two rates indicated that there was either no single climatic response
function for one or both compartments, and/or other edaphic factors influenced the translocation
effect. The most northern boreal soil showed a high thermosensitivity for recalcitrant
organic matter compartment, whereas the labile fraction was less sensitive to climate changes
for soils from more southern locations. Hence there was no single climatic function which
describe the decay rates for all compartments. At the end of the incubation period it was found
that the heat sum to achieve the same carbon losses was lower for soils in the north of the
transect than in the south. In the long term, therefore, for a given heat input, decomposition
rates would show larger increases in boreal northern sites than in warm temperate regions.
The changes in climate produced by soil translocation were more clearly reflected by
decomposition rates in the acid soils than for calcareous soils. This indicates that the physicochemical
environment can have important differential effects on microbial decomposition of
the labile and recalcitrant components of SOM. |
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