A global exploration of fine-root trait variation: opening the black box

Authors: FRESCHET, GRÉGOIRE - University Of Montpellier; VALVERDE-BARRANTES, OSCAR - Kent State University; TUCKER, CAROLINE - University Of Montpellier; CRAINE, JOSEPH - Arkansas State University; MCCORMACK, LUKE - Chinese Academy Of Sciences; VIOLLE, CYRILLE - University Of Montpellier; FORT, FLORIAN - Institut National De La Recherche Agronomique (INRA); BLACKWOOD, CHRISTOPHER - Kent State University; URBAN-MEAD, KATHERINE - University Of Montpellier; IVERSEN, COLLEEN - Oak Ridge National Laboratory; BONIS, ANNE - University Of Rennes, France; Comas, Louise; CORNELLISSEN, JOHANNES - Vrije University; DONG, MING - Hangzhou Normal University; GUO, DALI - Chinese Academy Of Sciences; HOBBIE, SARAH - University Of Minnesota; HOLDAWAY, ROBERT - Landcare Research; KEMBEL, STEVEN - University Of Quebec; MAKITA, NAOKI - Kyoto University; ONIPCHENKO, VLADIMIR - Lomonosov University; PICON-COCHARD, CATHERINE - Institut National De La Recherche Agronomique (INRA); REICH, PETER - University Of Minnesota; DE LA RIVA, ENRIQUE - Universidad De Cordoba; SMITH, STUART - University Of Aberdeen; SOUDZILOVSKAIA, NADEJDA - Leiden University; TJOELKER, MARK - Western Sydney University; WARDLE, DAVID - Swedish University Of Agricultural Sciences; ROUMET, CATHERINE - University Of Montpellier

Submitted to: Journal of Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2017
Publication Date: 4/19/2017
Citation: Freschet, G.T., Valverde-Barrantes, O.J., Tucker, C.M., Craine, J.M., McCormack, L.M., Violle, C., Fort, F., Blackwood, C., Urban-Mead, K.R., Iversen, C.M., Bonis, A., Comas, L.H., Cornellissen, J.H., Dong, M., Guo, D., Hobbie, S., Holdaway, R., Kembel, S.W., Makita, N., Onipchenko, V.G., Picon-Cochard, C., Reich, P.B., De La Riva, E.G., Smith, S.W., Soudzilovskaia, N.A., Tjoelker, M., Wardle, D.A., Roumet, C. 2017. A global exploration of fine-root trait variation: opening the black box. Journal of Ecology. doi:10.1111/1365-2745.12769.

Interpretive Summary: A major part of ecosystem functioning relies on below ground processes, which are governed by fine-root traits. This study examines fine-root traits collected worldwide (>9000 observations from >1100 species on 14 traits) to determine how traits vary across environments, plant growth forms and between legumes and non-legumes. Species from cold and temperate environments exhibited root traits that allow for rapid acquisition of soil resources, in contrast to species from arid and tropical biomes, which exhibited root traits that allow plants to conserve investment in root tissues. This pattern was opposite to that observed for aboveground traits, emphasizing the need to consider leaves and roots as partly independent entities, both in ecosystem functioning and biogeochemical cycling models. Additionally, our results bring to light the critical lack of knowledge about which fine-root traits are most informative for plant and ecosystem functioning, the current need for better standardization of how fine-roots are classified and the necessary separation of data collected from unnatural versus natural growing conditions. Several future research directions are proposed. Keywords: database; fine roots; functional traits; phylogeny; climate; plant growth form; N2-fixation; root sampling

Technical Abstract: A major part of ecosystem functioning relies on processes below ground, which are governed by fine root traits. This study synthesizes published and unpublished fine-root trait data available worldwide (>9000 observations from >1100 species on 14 traits) and examines their ecological value and global representation, specifically examining trait variation across biomes, plant growth forms and between N2-fixers and non-fixers. Species from cold and temperate biomes exhibited a syndrome of root traits known to favour resource acquisition, whereas species from arid and tropical biomes showed a resource conservation syndrome; a pattern opposite to this observed for aboveground traits. Such findings suggest that leaf and fine-root functional characteristics are unlikely to be consistently mirrored worldwide, and emphasize the need to consider leaves and roots as partly independent entities, both in ecosystem functioning and biogeochemical cycling models. Additionally, our results bring to light the critical lack of knowledge about those fine-root traits most informative for plant and ecosystem functioning, the current need for better standardization of fine-root classification and the necessary discrimination of results from controlled versus natural conditions. Several future research directions are proposed. Keywords: database; fine roots; functional traits; phylogeny; climate; plant growth form; N2-fixation; root sampling