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Abstract

Aims The partitioning of the total soil CO2 efflux into
its two main components: respiration from roots (and
root-associated organisms) and microbial respiration
(by means of soil organic matter (SOM) and litter
decomposition), is a major need in soil carbon dynamics
studies in order to understand if a soil is a net sink or
source of carbon.
Methods The heterotrophic component of the CO2
efflux was estimated for 11 forest sites as the ratio
between the carbon stocks of different SOM pools and
previously published (Δ14C derived) turnover times. The autotrophic component, including root and rootassociated respiration, was calculated the heterotrophic component from total soil chamber
measured CO2 efflux.
Results Results suggested that, on average, 50.4 % of
total soil CO2 efflux was derived from the respiration
of the living roots, 42.4 % from decomposition of the
litter layers and less than 10 % from decomposition of
belowground SOM.
Conclusions The Δ14C method proved to be an efficient
tool by which to partition soil CO2 efflux and
quantify the contribution of the different components
of soil respiration. However the average calculated
heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO2 efflux partitioning (one performed in the same study by subtracting area; the other a meta-analysis of soil respiration partitioning).
These differences were probably due to the
heterogeneity of the SOM fraction and to a suboptimal choice of the litter sampling period.