Mixing Eucalyptus and Acacia trees leads to fine root over-yielding and vertical segregation between species
2013
Laclau, Jean-Paul | Nouvellon, Yann | Reine, Caroline | de Moraes Goncalves, Jose Leonardo | Krushe, Alex Vladimir | Jourdan, Christophe | Le Maire, Guerric | Bouillet, Jean-Pierre | Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | UNESP, Dept Recursos Nat ; Universidade Estadual Paulista Júlio de Mesquita Filho = São Paulo State University (UNESP) | Instituto de Astronomia, Geofísica e Ciências Atmosféricas [São Paulo] (IAG) ; Universidade de São Paulo = University of São Paulo (USP) | Laboratoire Sols et Environnement (LSE) ; Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL) | Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ) ; Universidade de São Paulo = University of São Paulo (USP) | Centro de Energia Nuclear na Agricultura (CENA) ; Universidade de São Paulo = University of São Paulo (USP) | Agence Nationale de la Recherche (Intensfix) [ANR-2010-STRA-004]; FAPESP Thematic Project [2010/16623-9]; CIRAD (ATP Neucapalm); USP-COFECUB project [22193PA]; European Integrated Project Ultra Low CO2 Steelmaking (ULCOS) [n515960]
The consequences of diversity on belowground processes are still poorly known in tropical forests. The distributions of very fine roots (diameter < 1 mm) and fine roots (diameter < 3 mm) were studied in a randomized block design close to the harvest age of fast-growing plantations. A replacement series was set up in Brazil with mono-specific Eucalyptus grandis (100E) and Acacia mangium (100A) stands and a mixture with the same stocking density and 50 % of each species (50A:50E). The total fine root (FR) biomass down to a depth of 2 m was about 27 % higher in 50A:50E than in 100A and 100E. Fine root over-yielding in 50A:50E resulted from a 72 % rise in E. grandis fine root biomass per tree relative to 100E, whereas A. mangium FR biomass per tree was 17 % lower than in 100A. Mixing A. mangium with E. grandis trees led to a drop in A. mangium FR biomass in the upper 50 cm of soil relative to 100A, partially balanced by a rise in deep soil layers. Our results highlight similarities in the effects of directional resources on leaf and FR distributions in the mixture, with A. mangium leaves below the E. grandis canopy and a low density of A. mangium fine roots in the resource-rich soil layers relative to monospecific stands. The vertical segregation of resource-absorbing organs did not lead to niche complementarity expected to increase the total biomass production.
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