title: Root biomass, turnover and net primary productivity of a coffee agroforestry system in Costa Rica: effects of soil depth, shade trees, distance to row and coffee age.
abstract: Background and Aims In Costa Rica, coffee (Coffea arabica) plants are often grown in agroforests. However, it is not known if shade-inducing trees reduce coffee plant biomass through root competition, and hence alter overall net primary productivity (NPP). We estimated biomass and NPP at the stand level, taking into account deep roots and the position of plants with regard to trees. Methods Stem growth and root biomass, turnover and decomposition were measured in mixed coffee/tree (Erythrina poeppigiana) plantations. Growth ring width and number at the stem base were estimated along with stem basal area on a range of plant sizes. Root biomass and fine root density were measured in trenches to a depth of 4 m. To take into account the below-ground heterogeneity of the agroforestry system, fine root turnover was measured by sequential soil coring (to a depth of 30 cm) over 1 year and at different locations (in full sun or under trees and in rows/inter-rows). Allometric relationships were used to calculate NPP of perennial components, which was then scaled up to the stand level. Key Results Annual ring width at the stem base increased up to 2·5 mm yr-1 with plant age (over a 44-year period). Nearly all (92 %) coffee root biomass was located in the top 1·5 m, and only 8 % from 1·5 m to a depth of 4 m. Perennial woody root biomass was 16 t ha-1 and NPP of perennial roots was 1·3 t ha-1 yr-1. Fine root biomass (0-30 cm) was two-fold higher in the row compared with between rows. Fine root biomass was 2·29 t ha-1 (12 % of total root biomass) and NPP of fine roots was 2·96 t ha-1 yr-1 (69 % of total root NPP). Fine root turnover was 1·3 yr-1 and lifespan was 0·8 years. Conclusions Coffee root systems comprised 49 % of the total plant biomass; such a high ratio is possibly a consequence of shoot pruning. There was no significant effect of trees on coffee fine root biomass, suggesting that coffee root systems are very competitive in the topsoil.
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.|CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.
authors.forename: Elsa
authors.initials: E
authors.lastname: Defrenet
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.|CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.
authors.forename: Olivier
authors.initials: O
authors.lastname: Roupsard
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.|CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.
authors.forename: Karel
authors.initials: K
authors.lastname: Van den Meersche
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.|El Colegio de la Frontera Sur, Departamento Agricultura, Sociedad y Ambiente, Unidad San Cristobal de Las Casas, Chiapas, México.|Consejo Nacional de Ciencia y Tecnologia, Ciudad de México, D.F., México.
authors.forename: Fabien
authors.initials: F
authors.lastname: Charbonnier
authors.affiliation: CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.
authors.forename: Junior
authors.initials: J
authors.lastname: Pastor Pérez-Molina
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Khac
authors.affiliation: CNRS, Centre d'Ecologie Fonctionnelle et Evolutive (CEFE, UMR 5175 CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
authors.forename: Iván
authors.initials: I
authors.lastname: Prieto
authors.affiliation: INRA - Botanique et bioinformatique de l'architecture des plantes (AMAP), Bd de la Lironde, TA A-51 / PS2, 34398 Montpellier cedex 5, France.
authors.forename: Alexia
authors.initials: A
authors.lastname: Stokes
authors.affiliation: CNRS, Centre d'Ecologie Fonctionnelle et Evolutive (CEFE, UMR 5175 CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Roumet
authors.affiliation: CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.|CIRAD, UMR SYSTEM, 2 Place Viala, Montpellier, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Rapidel
authors.affiliation: CATIE (Tropical Agricultural Centre for Research and Higher Education), 7170 Turrialba, Costa Rica.
authors.forename: Elias
authors.initials: E
authors.lastname: de Melo Virginio Filho
authors.affiliation: ICAFE, Produccion Sostenible, Unidad de investigacion, CICAFE, Costa Rica.
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Vargas
authors.affiliation: CNRS, Centre d'Ecologie Fonctionnelle et Evolutive (CEFE, UMR 5175 CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE), 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
authors.forename: Diego
authors.initials: D
authors.lastname: Robelo
authors.affiliation: Cafetalera Aquiares S.A., PO Box 362-7150 Turrialba, Costa Rica.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Barquero
authors.affiliation: CIRAD, UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 2, place Viala, 34060 Montpellier cedex 2, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Jourdan
keywords: 
            Coffea arabica
          ; 
            Erythrina poeppigiana
          ; Allometry; NPP; agroforestry; fine root decomposition; growth rings; sequential coring