Climate, soil and plant functional types as drivers of global fine-root trait variation

TL;DR: This study reveals both the large variation in fine-root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation.

Abstract: 1.Ecosystem functioning relies heavily on belowground processes, which are largely regulated by plant fine-roots and their functional traits. However, our knowledge of fine-root trait distribution relies to date on local- and regional-scale studies with limited numbers of species, growth forms and environmental variation. 2.We compiled a worldwide fine-root trait dataset, featuring 1115 species from contrasting climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the influence of plant functional types, soil and climate variables, and the degree of manipulation of plant growing conditions on species fine-root trait variation. Most particularly, we tested the competing hypotheses that fine-root traits typical of faster return on investment would be most strongly associated with conditions of limiting versus favourable soil resource availability. We accounted for both data source and species phylogenetic relatedness. 3.We demonstrate that (1) Climate conditions promoting soil fertility relate negatively to fine-root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine-root diameter and negative effect on specific root length (SRL), and a negative effect of rainfall on root nitrogen concentration; (2) Soil bulk density strongly influences species fine-root morphology, by favouring thicker, denser fine-roots; (3) Fine-roots from herbaceous species are on average finer and have higher SRL than those of woody species, and N2-fixing capacity positively relates to root nitrogen; (4) Plants growing in pots have higher SRL than those grown in the field. 4.Synthesis. This study reveals both the large variation in fine-root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation. Climate, particularly temperature, and plant functional types were the two strongest predictors of fine-root trait variation. High trait variation occurred at local scales, suggesting that wide-ranging belowground resource economics strategies are viable within most climatic areas and soil conditions.

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Comment citer ce document :
Freschet, G., Valverde-Barrantes , O. J., Tucker, Craine, J., McCormack, M. L., Violle, Fort,
F., Blackwood, Urban-Mead, Iversen, C. M., Bonis, A., Comas , L. H., Cornelissen, J. H. C.,
Dong, Guo, D., Hobbie , S. E., Holdaway, R., Kembel, S., Makita , N., Onipchenko , V. G.,
Picon-Cochard, C., Reich, P. B., De la Riva , E. G., Smith , S. W., Soudzilovskaia, N. A., Tjoelker,
M. G., Wardle, D. A., Roumet (2017). Climate, soil and plant functional types as drivers of
global fine-root trait variation. Journal of Ecology, 105 (5), 1182-1196. , DOI : 10.1111/1365-2745.12769
Accepted Article
This article has been accepted for publication and undergone full peer review but has not
been through the copyediting, typesetting, pagination and proofreading process, which may
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doi: 10.1111/1365-2745.12769
This article is protected by copyright. All rights reserved.
DR. GRÉGOIRE THOMAS FRESCHET (Orcid ID : 0000-0002-8830-3860)
Received Date : 09-Dec-2016
Revised Date : 23-Feb-2017
Accepted Date : 28-Feb-2017
Article type : Standard Papers
Handling Editor: James Cahill
Title: Climate, soil and plant functional types as drivers of global fine-root trait variation
Type of article: Standard Papers
Short title: Global variation in fine-root traits
Authors’ names and addresses:
Grégoire T. Freschet
1*
, Oscar J. Valverde-Barrantes
2†
, Caroline M. Tucker
1
, Joseph M.
Craine
3
, M. Luke McCormack
4
, Cyrille Violle
1
, Florian Fort
1,5
, Christopher B. Blackwood
2
,
Katherine R. Urban-Mead
1
, Colleen M. Iversen
6
, Anne Bonis
7
, Louise H. Comas
8
, Johannes
H. C. Cornelissen
9
, Ming Dong
10
, Dali Guo
11
, Sarah E. Hobbie
12
, Robert J. Holdaway
13
,
Steven W. Kembel
14
, Naoki Makita
15
, Vladimir G. Onipchenko
16
, Catherine Picon-
Cochard
17
, Peter B. Reich
18, 19
, Enrique G. de la Riva
20
, Stuart W. Smith
21
, Nadejda A.
Soudzilovskaia
22
, Mark G. Tjoelker
19
, David A. Wardle
23
, Catherine Roumet
1
1
Centre d’Ecologie Fonctionnelle et Evolutive, UMR 5175 (CNRS – Université de
Montpellier – Université Paul-Valéry Montpellier – EPHE), 1919 route de Mende,
Montpellier 34293, France
2
Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
3
Jonah Ventures, Manhattan, KS 66502, USA

Version postprint
Comment citer ce document :
Freschet, G., Valverde-Barrantes , O. J., Tucker, Craine, J., McCormack, M. L., Violle, Fort,
F., Blackwood, Urban-Mead, Iversen, C. M., Bonis, A., Comas , L. H., Cornelissen, J. H. C.,
Dong, Guo, D., Hobbie , S. E., Holdaway, R., Kembel, S., Makita , N., Onipchenko , V. G.,
Picon-Cochard, C., Reich, P. B., De la Riva , E. G., Smith , S. W., Soudzilovskaia, N. A., Tjoelker,
M. G., Wardle, D. A., Roumet (2017). Climate, soil and plant functional types as drivers of
global fine-root trait variation. Journal of Ecology, 105 (5), 1182-1196. , DOI : 10.1111/1365-2745.12769
Accepted Article
This article is protected by copyright. All rights reserved.
4
Department of Plant Biology, University of Minnesota, 1445 Gortner Avenue, St. Paul, MN
55108, USA
5
INRA, UMR 1248 AGIR, Centre de recherche de Toulouse, CS 52627, 31326 Castanet-
Tolosan Cedex, France
6
Climate Change Science Institute and Environmental Sciences Division, Oak Ridge
National Laboratory, Oak Ridge, TN 37831, USA
7
UMR 6553 ECOBIO: Ecosystems, Biodiversity, Evolution, CNRS-University of Rennes 1,
OSU Rennes, France
8
USDA-ARS Water Management Research Unit, 2150 Centre Avenue, Bldg D Suite 320,
Fort Collins, CO 80526, USA
9
Systems Ecology, Department of Ecological Sciences, Vrije Universiteit, de Boelelaan
1085, Amsterdam 1081 HV, the Netherlands
10
Key Laboratory of Hangzhou City for Ecosystem Protection and Restoration, College of
Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
11
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic
Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101,
China
12
Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN
55108, USA
13
Landcare Research, PO Box 69040, Lincoln 7640, New Zealand
14
Département des sciences biologiques, Université du Québec à Montréal, Montréal,
Québec, Canada
15
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
16
Department of Geobotany, Faculty of Biology, Moscow State Lomonosov University,
119234 Moscow, Russia

Version postprint
Comment citer ce document :
Freschet, G., Valverde-Barrantes , O. J., Tucker, Craine, J., McCormack, M. L., Violle, Fort,
F., Blackwood, Urban-Mead, Iversen, C. M., Bonis, A., Comas , L. H., Cornelissen, J. H. C.,
Dong, Guo, D., Hobbie , S. E., Holdaway, R., Kembel, S., Makita , N., Onipchenko , V. G.,
Picon-Cochard, C., Reich, P. B., De la Riva , E. G., Smith , S. W., Soudzilovskaia, N. A., Tjoelker,
M. G., Wardle, D. A., Roumet (2017). Climate, soil and plant functional types as drivers of
global fine-root trait variation. Journal of Ecology, 105 (5), 1182-1196. , DOI : 10.1111/1365-2745.12769
Accepted Article
This article is protected by copyright. All rights reserved.
17
INRA, UR874, Grassland Ecosystem Research Team, 5 chemin de Beaulieu, 63039
Clermont-Ferrand, France
18
Department of Forest Resources, University of Minnesota, St. Paul, MN 55108, USA
19
Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797,
Penrith, NSW 2751, Australia
20
Área de Ecología, Facultad de Ciencias, Universidad de Córdoba, 14071 Córdoba, Spain
21
Department of Biology, Norwegian University of Science and Technology, NO-7491
Trondheim, Norway
22
Conservation Biology Department, Institute of Environmental Sciences, CML, Leiden
University, Einsteinweg 2, 2333 CC Leiden, The Netherlands
23
Department of Forest Ecology and Management, Swedish University of Agricultural
Sciences, SE901-83 Umea, Sweden
†
Present address: International Center for Tropical Botany, Department of Biological
Sciences, Florida International University, 11200 SW 8th Street, OE 243 Miami, FL 33199,
USA
* Correspondence:
Grégoire T. Freschet; Address: Centre d’Ecologie Fonctionnelle et Evolutive, 1919 route de
Mende, 34293 Montpellier cedex 5, France. Phone: 0033 (0)467613340; Fax:
0033(0)467613336; Email: gregoire.freschet@cefe.cnrs.fr

Version postprint
Comment citer ce document :
Freschet, G., Valverde-Barrantes , O. J., Tucker, Craine, J., McCormack, M. L., Violle, Fort,
F., Blackwood, Urban-Mead, Iversen, C. M., Bonis, A., Comas , L. H., Cornelissen, J. H. C.,
Dong, Guo, D., Hobbie , S. E., Holdaway, R., Kembel, S., Makita , N., Onipchenko , V. G.,
Picon-Cochard, C., Reich, P. B., De la Riva , E. G., Smith , S. W., Soudzilovskaia, N. A., Tjoelker,
M. G., Wardle, D. A., Roumet (2017). Climate, soil and plant functional types as drivers of
global fine-root trait variation. Journal of Ecology, 105 (5), 1182-1196. , DOI : 10.1111/1365-2745.12769
Accepted Article
This article is protected by copyright. All rights reserved.
ABSTRACT
1. Ecosystem functioning relies heavily on belowground processes, which are largely
regulated by plant fine-roots and their functional traits. However, our knowledge of fine-root
trait distribution relies to date on local- and regional-scale studies with limited numbers of
species, growth forms and environmental variation.
2. We compiled a worldwide fine-root trait dataset, featuring 1115 species from contrasting
climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the
influence of plant functional types, soil and climate variables, and the degree of manipulation
of plant growing conditions on species fine-root trait variation. Most particularly, we tested
the competing hypotheses that fine-root traits typical of faster return on investment would be
most strongly associated with conditions of limiting versus favourable soil resource
availability. We accounted for both data source and species phylogenetic relatedness.
3. We demonstrate that (1) Climate conditions promoting soil fertility relate negatively to
fine-root traits favouring fast soil resource acquisition, with a particularly strong positive
effect of temperature on fine-root diameter and negative effect on specific root length (SRL),
and a negative effect of rainfall on root nitrogen concentration; (2) Soil bulk density strongly
influences species fine-root morphology, by favouring thicker, denser fine-roots; (3) Fine-
roots from herbaceous species are on average finer and have higher SRL than those of woody
species, and N
2
-fixing capacity positively relates to root nitrogen; (4) Plants growing in pots
have higher SRL than those grown in the field.
4. Synthesis. This study reveals both the large variation in fine-root traits encountered
globally and the relevance of several key plant functional types and soil and climate variables
for explaining a substantial part of this variation. Climate, particularly temperature, and plant
functional types were the two strongest predictors of fine-root trait variation. High trait

Version postprint
Comment citer ce document :
Freschet, G., Valverde-Barrantes , O. J., Tucker, Craine, J., McCormack, M. L., Violle, Fort,
F., Blackwood, Urban-Mead, Iversen, C. M., Bonis, A., Comas , L. H., Cornelissen, J. H. C.,
Dong, Guo, D., Hobbie , S. E., Holdaway, R., Kembel, S., Makita , N., Onipchenko , V. G.,
Picon-Cochard, C., Reich, P. B., De la Riva , E. G., Smith , S. W., Soudzilovskaia, N. A., Tjoelker,
M. G., Wardle, D. A., Roumet (2017). Climate, soil and plant functional types as drivers of
global fine-root trait variation. Journal of Ecology, 105 (5), 1182-1196. , DOI : 10.1111/1365-2745.12769
Accepted Article
This article is protected by copyright. All rights reserved.
variation occurred at local scales, suggesting that wide-ranging belowground resource
economics strategies are viable within most climatic areas and soil conditions.
Keywords: database; fine roots; functional biogeography; functional traits; N
2
-fixation;
phylogeny; plant growth form; plant resource economics; root function; soil properties
Introduction
Fine roots perform essential functions for plants including nutrient and water acquisition
(Waisel et al. 2002) and influence a broad spectrum of ecological processes, from net primary
production (Cadotte et al. 2009) to nutrient cycling (Freschet et al. 2013b; Hobbie 2015) and
soil formation (Iversen 2010; Clemmensen et al. 2013; Bardgett et al. 2014). The influence of
fine roots on these plant and ecosystem processes is largely mediated by their morphological,
chemical and physiological traits (Bardgett et al. 2014). Similarly, differences in fine-root
traits among species are thought to represent their evolutionary history and adaptations to a
wide range of biotic and abiotic factors (Kembel & Cahill 2011; Comas et al. 2012).
As evidenced by a number of global syntheses on these topics, a considerable number of
studies have explored the variation in ecosystem root biomass (e.g. Jackson et al. 1997), their
vertical distribution in soils (Schenk & Jackson 2002), their fluctuations in productivity (Vogt
et al. 1995) and turnover (Gill & Jackson 2000). Accounts of variation in morphological or
chemical fine-root traits across ecosystems are also relatively common (e.g. Jackson et al.
1997; Iversen et al. 2015). However, to accurately determine the drivers of fine-root trait
distribution, we need to focus most particularly on their variation at the level of species and
plant individuals (e.g. Laughlin 2014; Violle et al. 2014), similar to what has been performed
for leaf traits (e.g. Wright et al. 2005b; Maire et al. 2015). Current accounts of species fine-
root trait variation are to date most often limited to the regional scale, focus either on woody