Soil aggregate stability in Mediterranean and tropical agro-ecosystems: effect of plant roots and soil characteristics
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Our aim was to determine the effect of soil characteristics and root traits on soil aggregate stability at an inter- and intra-site scale in a range of agro-ecosystems. We also evaluated the effect of soil depth and the type of land use on aggregate stability.
Soil aggregate stability, soil physicochemical properties and fine root traits were measured along land use gradients (from monocultures to agroforestry systems and forests), at two soil depths at four sites (Mediterranean and tropical climates) with contrasting soils (Andosol, Ferralsol, Leptosol and Fluvisol).
Aggregate stability was much lower in deep than in surface soil layers, likely linked to lower soil organic carbon (SOC) and lower root mass density (RMD). Locally, and consistently in all sites, land use intensification degrades soil aggregate stability, mainly in surface soil layers. Soil organic carbon, cation exchange capacity and root traits: water-soluble compounds, lignin and medium root length proportion were the most important drivers of aggregate stability at the inter-site level, whereas SOC, root mass and root length densities (RMD, RLD) were the main drivers at the intra-site level.
Overall, the data suggest different controls on soil aggregate stability globally (soil) and locally (roots). Conversion from forests to agricultural land will likely lead to greater C losses through a loss of aggregate stability and increased soil erosion.
KeywordsAggregate stability Land use Root traits Soil depth Soil organic carbon
We are grateful to the Agence Nationale de la Recherche in France for funding this work (Ecosfix ANR-10-STRA-003-001) and the Ecosfix Consortium for helping collect the root material at the different sites. Alain Pierret (IRD), Olivier Roupsard (CIRAD) and Christian Dupraz (INRA) provided the necessary technical and human infrastructure at the different field sites in Laos, Costa Rica and Restinclières, respectively. We are grateful to Luis Merino-Martin (INRA) for helpful comments to improve the manuscript and to Jérome Pérez (INRA) who helped develop a database to store the project data. All plant trait morphological and chemical analyses were conducted at the Plateforme d’Analyses Chimiques en Ecologie (technical facilities of the Labex Centre Méditerranéen de l’Environnement et de la Biodiversité) and the soil stability aggregate analyses were conducted at LISAH in Montpellier.
AS, YLB, IP and CR planned and designed the research and all authors conducted the fieldwork. JN, JM, MV, SH and YLB measured soil variables, IP and CR measured root traits, IP compiled and analyzed the data, YLB, IP and CR wrote the manuscript and all authors contributed to the final version.
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