Root traits explain plant species distributions along climatic gradients yet challenge the nature of ecological trade-offs

Daniel C Laughlin (1) , Liesje Mommer (2) , Francesco Maria Sabatini (3, 4) , Helge Bruelheide (3, 4) , Thom W Kuyper (2) , M Luke Mccormack (5) , Joana Bergmann (6) , Grégoire T. Freschet (7) , Nathaly R Guerrero-Ramírez (8) , Colleen M Iversen (9) , Jens Kattge (3, 10) , Ina C Meier (11) , Hendrik Poorter (12, 13) , Catherine Roumet (14) , Marina Semchenko (15, 16) , Christopher J Sweeney (15) , Oscar J Valverde-Barrantes (17) , Fons van Der Plas (2, 18) , Jasper van Ruijven (2) , Larry M York (19) , Isabelle Aubin (20) , Olivia R Burge (21) , Chaeho Byun (22) , Renata Ćušterevska (23) , Jürgen Dengler (3, 24, 25) , Estelle Forey (26) , Greg R Guerin (27, 28) , Bruno Hérault (29, 30) , Robert B Jackson (31, 32) , Dirk Nikolaus Karger (33) , Jonathan Roger Michel Henri Lenoir (34) , Tatiana Lysenko (35) , Patrick Meir (36, 37) , Ülo Niinemets (38) , Wim A Ozinga (2) , Josep Peñuelas (39) , Peter B Reich (40, 41) , Marco Schmidt (42) , Franziska Schrodt (43) , Eduardo Velázquez (44) , Alexandra Weigelt (3, 18)

1 UW - University of Wyoming
2 WUR - Wageningen University and Research [Wageningen]
3 iDiv - German Centre for Integrative Biodiversity Research
4 Martin-Luther-University Halle-Wittenberg
5 The Morton Arboretum
6 ZALF - Leibniz-Zentrum für Agrarlandschaftsforschung = Leibniz Centre for Agricultural Landscape Research
7 SETE - Station d'Ecologie Théorique et Expérimentale
8 Georg-August-University = Georg-August-Universität Göttingen
9 ORNL - Oak Ridge National Laboratory [Oak Ridge]
10 MPI-BGC - Max Planck Institute for Biogeochemistry
11 UHH - Universität Hamburg
12 IBG-2
13 Macquarie University
14 CEFE - Centre d’Ecologie Fonctionnelle et Evolutive
15 University of Manchester [Manchester]
16 University of Tartu
17 FIU - Florida International University [Miami]
18 Leipzig University / Universität Leipzig
19 Noble Research Institute
20 GLFC - Great Lakes Forestry Centre
21 Manaaki Whenua – Landcare Research [Lincoln]
22 Andong National University
23 UKIM - Ss. Cyril and Methodius University in Skopje
24 ZHAW - Zürcher Hochschule für Angewandte Wissenschaften = Zurich University of Applied Sciences
25 University of Bayreuth
26 ECODIV - Département écologie et biodiversité des milieux forestiers, prairiaux et aquatiques
27 University of Adelaide
28 UQ [All campuses : Brisbane, Dutton Park Gatton, Herston, St Lucia and other locations] - The University of Queensland
29 UPR Forêts et Sociétés - Forêts et Sociétés
30 INP-HB - Institut National Polytechnique Félix Houphouët-Boigny [Yamoussoukro]
31 Stanford University
32 Stanford Woods Institute for the Environment
33 WSL - Institut Fédéral de Recherches sur la Forêt, la Neige et le Paysage
34 EDYSAN - Ecologie et Dynamique des Systèmes Anthropisés - UMR CNRS 7058
35 RAS - Russian Academy of Sciences [Moscow]
36 ANU - Australian National University
37 Edin. - University of Edinburgh
38 EMU - Estonian University of Life Sciences
39 CREAF - Centre for Ecological Research and Applied Forestries
40 UMN - University of Minnesota System
41 Western Sydney University
42 SBiK-F - Senckenberg Biodiversity and Climate Research Centre
43 UON - University of Nottingham, UK
44 UVa - Universidad de Valladolid [Valladolid]

Ecological theory is built on trade-offs, where trait differences among species evolved as adaptations to different environments. Trade-offs are often assumed to be bidirectional, where opposite ends of a gradient in trait values confer advantages in different environments. However, unidirectional benefits could be widespread if extreme trait values confer advantages at one end of an environmental gradient, whereas a wide range of trait values are equally beneficial at the other end. Here, we show that root traits explain species occurrences along broad gradients of temperature and water availability, but model predictions only resembled trade-offs in two out of 24 models. Forest species with low specific root length and high root tissue density (RTD) were more likely to occur in warm climates but species with high specific root length and low RTD were more likely to occur in cold climates. Unidirectional benefits were more prevalent than trade-offs: for example, species with large-diameter roots and high RTD were more commonly associated with dry climates, but species with the opposite trait values were not associated with wet climates. Directional selection for traits consistently occurred in cold or dry climates, whereas a diversity of root trait values were equally viable in warm or wet climates. Explicit integration of unidirectional benefits into ecological theory is needed to advance our understanding of the consequences of trait variation on species responses to environmental change.

Mots clés: Biogeography; Community ecology; Ecophysiology; Natural variation in plants

Domaines: Sciences de l'environnement

Daniel C Laughlin, Liesje Mommer, Francesco Maria Sabatini, Helge Bruelheide, Thom W Kuyper, et al.. Root traits explain plant species distributions along climatic gradients yet challenge the nature of ecological trade-offs. Nature Ecology & Evolution, 2021, 5 (8), pp.1123-1134. ⟨10.1038/s41559-021-01471-7⟩. ⟨hal-03260203⟩