Competition with winter crops induces deeper rooting of walnut trees in a Mediterranean alley cropping agroforestry system
2015
Cardinael, Rémi | Mao, Zhun | Prieto, Ivan | Stokes, Alexia | Dupraz, Christian | Kim, John | Jourdan, Christophe | Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS) ; Institut National de la Recherche Agronomique (INRA)-AgroParisTech | Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [Occitanie]) | Centre d’Ecologie Fonctionnelle et Evolutive (CEFE) ; Université Paul-Valéry - Montpellier 3 (UPVM)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École Pratique des Hautes Études (EPHE) ; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [Occitanie])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | Fonctionnement et conduite des systèmes de culture tropicaux et méditerranéens (UMR SYSTEM) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre International de Hautes Etudes Agronomiques Méditerranéennes - Institut Agronomique Méditerranéen de Montpellier (CIHEAM-IAMM) ; Centre International de Hautes Études Agronomiques Méditerranéennes (CIHEAM)-Centre International de Hautes Études Agronomiques Méditerranéennes (CIHEAM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | 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) | French ANR : ANR-2010-STRA-003-01. ADEME | ANR-10-STRA-0003,ECOSFIX,Services écosystémiques des racines – redistribution hydrique, séquestration du carbone et fixation du sol(2010)
[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN
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Show more [+] Less [-]English. Background and Aims: Characterising the spatial distribution of tree fine roots (diameter ≤ 2 mm) is fundamental for a better understanding of tree functioning in agroforestry ecosystems. The absorptive function of fine roots is closely associated to aboveground tree performance and the amount of competition experienced by a tree partly depends on how root spatial distribution varies with soil depth in mixed systems. We therefore compared root interception densities (RID) and fine root orientation of trees grown in an alley cropping agroforestry stand (AF) with those in a monocropped (M) tree stand. Methods: Fieldwork was conducted in two 17 year old hybrid walnut (Juglans regia × nigra cv. NG23) stands in southern France: one was an alley cropping agroforestry stand with durum wheat (Triticum turgidum L. subsp. durum) intercropped in strips between tree rows and the second was a monocropped stand with a natural understorey. One pit was dug in each stand to a depth of 1.6 m, and an additional pit was dug in the agroforestry stand to a depth of 4.0 m to examine the tree root distribution below the crop maximum rooting depth. Root intercepts were mapped on trench walls and soil cubes were sampled to assess 3D root orientation, and to establish a predictive model of root length densities (RLD).Results: In the monocropped stand, root mapping evidenced a very high RID in the top 0.5 m and a slight decrease with increasing soil depth, whereas in the agroforestry stand, RID was much lower for the same depth, but roots occupied a higher volume of soil. In the agroforestry stand, RID and RLD were higher within the tree row than in the inter-row at deeper depths. Tree fine roots in both stands were not preferentially oriented from the soil surface until a depth of 1.5 m, beneath which fine roots in the agroforestry stand were significantly more vertically oriented.Conclusions: Fine roots of intercropped walnut trees went significantly deeper indicating strong plasticity of root distribution. Deeper root systems would reduce direct competition from the crop and enable trees to access deeper water tables not available to the crop.
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