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The manipulation of organic residues affects tree growth and heterotrophic CO2 efflux inatropical Eucalyptus plantation

Versini A., Nouvellon Y., Laclau J.P., Kinana A., Mareschal L., Zeller B., Ranger J., Epron D.. 2013. Forest Ecology and Management, 301 : p. 79-88.

DOI: 10.1016/j.foreco.2012.07.045

Fast-growing plantationsareincreasinglybeingestablishedontropicalsoils,wherefertilityislargely supported bysoilorganicmatter(SOM)andwheredifferentmanagementoptionsofharvestorganicres- idues isthoughttoimpactthelong-termsustainabilityoftheseplantations.Theobjectivesofthisstudy were: (1)toquantifytheeffectofcontrastingmethodsoforganicresiduemanagementontreegrowth and soilCO2 effluxes inthefirst2yearsafterplantingand(2)toevaluatetheimpactoforganicresidue manipulations onthemineralizationofsoilorganicmatteroverthelengthoftheexperiment.Threetreat- ments weresetupin0.125haplotsandreplicatedinthreeblocksattheharvestingofaCongolese Euca-lyptus stand, resultinginanabovegroundorganicresiduemassrangingfrom0to6.3kgm_2. The mineralization ofSOMwasdeducedineachtreatmentbypartitioningsourcesofsoilCO2 effluxes using decomposition experimentsandbyupscalingspecificrootrespiration.SoilCO2 effluxes weregreatly affected byseasonsandorganicresiduemanipulation,althoughtherewerenosignificantchangesintop- soil watercontentandtopsoiltemperatureovermostofthestudyperiod.Abovegroundorganicresidue was thefirstcontributortosoilCO2 efflux inthetwotreatmentswithalitterlayer.Organicresidueman- agement didnotsignificantlyinfluencethemineralizationofSOMinourstudy,probablyduetothelow quality of Eucalyptus litter, ortothehypotheticallackofdissolvedorganiccarbontransfersfromlitterto soil. AstrongrelationshipwasfoundbetweencumulativeheterotrophicCO2 efflux andtreegrowth,sup- porting thehypothesisthattheearlygrowthof Eucalyptus trees inasandytropicalsoilislargelydepen- dent onthenutrientsreleasedbythedecompositionoforganicresidues.

Mots-clés : eucalyptus; résidu de récolte; croissance; respiration du sol; minéralisation; matière organique du sol; congo

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