Stable C isotope for partitioning ecosystem CO2 fluxes: from the theoretical background, the laboratory and methodological implementation to field study cases in Mediterranean ecosystems

Comparisons of forest stands of different age classes along a chronosequence have been used to investigate the effects of management on forest carbon cycling. We have estimated the soil CO2 efflux (soil respiration) in two stands of different ages (0 and 20 years) along a chronosequence of Quercus cerris L. in Central Italy. The age sequence of the forest stands is the result of coppicing, a typical Italian forest management practice. Although coppicing is a well-known silvicultural practice, very little is known about the response of the belowground forest component and, consequently, about the implications of coppicing for carbon sequestration in forests. We have measured soil respiration, temperature and moisture during two 24 hour¬campaigns in June and July by comparing a recently coppiced stand with a 20 year old stand. We found slightly lower soil respiration rates in the coppiced stand, probably due to the scarcer water availability. There were small differences in the isotopic composition of soil derived CO2 between the two stands and a high variability within the time series. Our data indicate that soil C loss is not significantly reduced immediately after coppicing and given the obvious decrease in C assimilation in this phase of forest growth; a significant loss from the system is expected during the early stages of forest re-growth