Species and root traits impact macroaggregation in the rhizospheric soil of a Mediterranean common garden experiment
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Background and aims
We evaluated the influence of plant species and life forms on soil aggregate distribution among size-classes, total macroaggregate mass and aggregate mean weight diameter (MWD), and examined how specific root traits were related to these aggregation variables.
We analyzed the soil attached to the roots (i.e., rhizospheric soil) under 13 Mediterranean species grown in monocultures in a common garden experiment for four years, and compared it to a bare soil. The mass distribution of aggregates in six size-classes and aggregate MWD were calculated, both on a rhizospheric soil and root biomass basis.
Compared to bare soil, macroaggregate mass increased by an average of 13% in the presence of plants, with a strong effect of species and life forms (both P < 0.0001); some species such as Sanguisorba minor showing increases of up to ~40%. Although the soil under graminoids had a greater macroaggregate mass, their MWD was lower than under non-woody dicots. Large (2000–1000 μm) and intermediate (1000–500 μm) macroaggregate mass increased with root mass and length density and decreased with root lignin concentration, while very large macroaggregate (6000–2000 μm) mass and the MWD increased with root soluble compound concentration.
Species and life forms differently influenced the distribution of macroaggregates among size-classes and aggregate MWD. Easily-decomposable roots with traits related to resource acquisition (i.e., high fine root length, high water-soluble compound concentration) are more favorable for the development of water-stable macroaggregates than roots traits related to resource conservation (high lignin concentration, thick roots).
KeywordsSoil aggregate stability Macroaggregation Plant species Plant life forms Root traits Rhizospheric soil
The authors would like to thank the Fonds de recherche du Québec – Nature et technologies for financial support through a postdoctoral fellowship awarded to Vincent Poirier, the Natural Sciences and Engineering Research Council of Canada (NSERC) for a Discovery grant awarded to Alison D. Munson., the Groupement de Recherche International “Dynamique de la biodiversité et traits d’histoire de vie” (GDRI-n°BFC 44745, CNRS, France) and the Agence Nationale de la Recherche (project O2LA, ANR-09-STRA-09) for financial support through the experiment. Thanks are due to the staff of the Plateforme d’Analyses Chimiques en Ecologie (PACE) and of the CEFE experimental field (technical facilities of the Labex Centre Méditerranean de l’Environnement et de la Biodiversité, CEMEB). We are also thankful to Étienne Laliberté, Claire Chenu and Grégoire Freschet for helpful comments and discussions.
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