Agriculture, Ecosystems and Environment 148 (2012) 102–110 Contents lists available at SciVerse ScienceDirect Agriculture, Ecosystems and Environment jo u r n al hom ep age: www.elsevier.com/locate/agee Changes in carbon stock and greenhouse gas balance in a coffee (Coffea arabica) monoculture versus an agroforestry system with Inga densiflora, in Costa Rica Kristell Hergoualc’h a,b,c,∗ , Eric Blanchart d , Ute Skiba e , Catherine Hénault f , Jean-Michel Harmand a a CIRAD (Centre de coopération International en Recherche Agronomique pour le Développement), UMR Eco&Sols – Ecologie Fonctionnelle & Biogéochimie des Sols & Agroécosystèmes, Place Viala, F34060 Montpellier, France b CATIE (Centro Agronómico Tropical de Investigación y Ense˜ nanza), Departamento de Agricultura y Agroforestería, 7170 Turrialba, Costa Rica c CIFOR (Center for International Forestry Research), Jl. CIFOR, Situ Gede, Bogor 16115, Indonesia d IRD (Institut de Recherche pour le Développement), UMR Eco&Sols – Ecologie Fonctionnelle & Biogéochimie des Sols & Agroécosystèmes, Place Viala, F34060 Montpellier, France e CEH (Center of Ecology and Hydrology), Bush Estate, Penicuik EH26 0QB, Scotland, UK f INRA (Institut National de Recherche en Agronomie), UMR Microbiologie et Géochimie des Sols, 17 rue de Sully – BP 86510, 21065 Dijon Cedex, France a r t i c l e i n f o Article history: Received 12 May 2011 Received in revised form 25 November 2011 Accepted 26 November 2011 Keywords: Andosol Carbon sequestration Central America Global warming potential Leguminous tree Soil organic matter a b s t r a c t Agroforestry represents an opportunity to reduce CO 2 concentrations in the atmosphere by increasing carbon (C) stocks in agricultural lands. Agroforestry practices may also promote mineral N fertilization and the use of N 2 -fixing legumes that favor the emission of non-CO 2 greenhouse gases (GHG) (N 2 O and CH 4 ). The present study evaluates the net GHG balance in two adjacent coffee plantations, both highly fertilized (250 kg N ha -1 year -1 ): a monoculture (CM) and a culture shaded by the N 2 -fixing legume tree species Inga densiflora (CIn). C stocks, soil N 2 O emissions and CH 4 uptakes were measured during the first cycle of both plantations. During a 3-year period (6–9 years after the establishment of the sys- tems), soil C in the upper 10 cm remained constant in the CIn plantation (+0.09 ± 0.58 Mg C ha -1 year -1 ) and decreased slightly but not significantly in the CM plantation (-0.43 ± 0.53 Mg C ha -1 year -1 ). Above- ground carbon stocks in the coffee monoculture and the agroforestry system amounted to 9.8 ± 0.4 and 25.2 ± 0.6 Mg C ha -1 , respectively, at 7 years after establishment. C storage rate in the phytomass was more than twice as large in the CIn compared to the CM system (4.6 ± 0.1 and 2.0 ± 0.1 Mg C ha -1 year -1 , respectively). Annual soil N 2 O emissions were 1.3 times larger in the CIn than in the CM plantation (5.8 ± 0.5 and 4.3 ± 0.3 kg N-N 2 O ha -1 year -1 , respectively). The net GHG balance at the soil scale calcu- lated from the changes in soil C stocks and N 2 O emissions, expressed in CO 2 equivalent, was negative in both coffee plantations indicating that the soil was a net source of GHG. Nevertheless this bal- ance was in favor of the agroforestry system. The net GHG balance at the plantation scale, which includes additionally C storage in the phytomass, was positive and about 4 times larger in the CIn (14.59 ± 2.20 Mg CO 2 eq ha -1 year -1 ) than in the CM plantation (3.83 ± 1.98 Mg CO 2 eq ha -1 year -1 ). Thus converting the coffee monoculture to the coffee agroforestry plantation shaded by the N 2 -fixing tree species I. densiflora would increase net atmospheric GHG removals by 10.76 ± 2.96 Mg CO 2 eq ha -1 year -1 during the first cycle of 8–9 years. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The concentration of CO 2 and other greenhouse gases (GHG) in the atmosphere has increased considerably over the last four decades (Rogner et al., 2007). This increase is mainly a result of the burning of fossil fuels and the conversion of tropical forests to agricultural production, which have caused negative changes in the global climate (Rogner et al., 2007). Reduction of GHG ∗ Corresponding author at: CIFOR ENV, PO Box 0113 BOCBD, Bogor 16000, Indonesia. Tel.: +62 251 8622100; fax: +62 251 8622622. E-mail address: k.hergoualch@cgiar.org (K. Hergoualc’h). concentrations in the atmosphere in order to mitigate climate change can be achieved through two major processes: (1) reducing anthropogenic emissions; and (2) creating and/or enhancing GHG sinks in the biosphere (Albrecht and Kandji, 2003; Oelbermann et al., 2004). By including trees in agricultural production systems, agroforestry offers a potential as biomass energy provider and thus presents interesting opportunities for CO 2 mitigation through the substitution of fossil fuel by wood energy and the protection of existing forests (Verchot et al., 2005). Moreover, agroforestry can increase the amount of carbon (C) stored in agricultural systems while still allowing for the growing of food crops (Montagnini and Nair, 2004). Tree components in agroforestry systems can be significant sinks of atmospheric C (De Miguel Maga ˜ na et al., 0167-8809/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2011.11.018