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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Carbon flux from plants to soil: roots are a below-ground source of phenolic secondary compounds in an alpine ecosystem
Auteurs :	Courtney L. Meier, Auteur ; Katharine N. Suding, Auteur ; William D. Bowman, Auteur
Type de document :	Article
Dans :	Journal of Ecology (96(3) MAY 2008)
Article en page(s) :	421-430
Langues:	Anglais
Résumé :	1. Phenolics are an important, biologically reactive component of the carbon (C) pool that moves from plants to soil. Once in soil, phenolics can regulate plant-soil feedbacks because of their influence on soil nitrogen biogeochemistry. 2. Roots are a largely overlooked potential source of below-ground phenolic C. We examined phenolic fluxes from plants to soil in an alpine ecosystem, where phenolics are associated with slow rates of nutrient cycling. Using a phenolic-rich forb (Acomastylis rossii) and a grass with low tissue phenolics (Deschampsia caespitosa), we asked whether leaves, leaf litter or roots are the dominant source of soil phenolics during the growing season. We also determined whether the composition of root-derived phenolics differed from that of leaf litter. 3. Both labile low molecular weight phenolics and tannins disappeared from A. rossii leaf litter over the winter. Evidence from this study and others indicates litter phenolics are not a significant source of labile C for soil microbes throughout the growing season. 4. In the field, levels of phenolics were higher under A. rossii canopies than under D. caespitosa canopies throughout the growing season. We also estimated significantly higher phenolic fluxes into soils for A. rossii than for D. caespitosa in the glasshouse. Field and glasshouse results suggest roots are an important source of these compounds. Furthermore, the phenolic chemistry of roots was different from that of leaf litter, indicating that the effects of root phenolics on soil processes and neighbouring plant growth may differ from those associated with leaves. 5. Synthesis. Based on our results, labile phenolic inputs from roots are likely to have a more important influence on soil nutrient dynamics during the alpine growing season than phenolic inputs from leaf litter. We suggest that roots may be the dominant input of labile phenolics to soil during the growing season in other ecosystems with seasonal patterns of plant growth and senescence. These observations are critical to our understanding of how phenolic-rich species may interact with soil microbes to influence soil nutrient cycling and shape the soil resource environment.

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