Authors: Yann Nouvellon Daniel Epron Claire Marsden Antoine Kinana Guerric Le Maire Philippe Deleporte Laurent SaintAndré JeanPierre Bouillet JeanPaul Laclau
Publish Date: 2011/11/30
Volume: 111, Issue: 1-3, Pages: 515-533
Abstract
Land use changes such as savannah afforestation with eucalypts impact the soil carbon C balance therefore affecting soil CO2 efflux F s a major flux in the global C cycle We tested the hypothesis that F s increases with stand age after afforestation due to an increasing input of fresh organic matter to the forest floor In a Eucalyptus plantation established on coastal savannahs in Congo bimonthly measurements of F s were carried out for 1 year on three adjacent stands aged 09 44 and 137 years and presenting similar growth patterns Litterfall and litter accumulation on the forest floor were quantified over a chronosequence Equations were derived to estimate the contribution of litter decomposition to F s throughout the rotation Litterfall increased with stand age after savannah afforestation F s that was strongly correlated on a seasonal basis with soil water content SWC in all stands decreased between ages 09 year and 44 years due to savannah residue depletion and increased between ages 44 years and 137 years mainly because of an increasing amount of decomposing eucalypt litter The aboveground litter layer therefore appeared as a major source of CO2 whose contribution to F s in old stands was estimated to be about four times higher than that of the eucalyptderived soil organic C pool The high litter contribution to F s in older stands might explain why 137 yearsold stand F s was limited by moisture all year round whereas SWC did not limit F s for large parts of the year in the youngest stands
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