Many scientific disciplines are currently experiencing a 'reproducibility crisis' because numerous scientific findings cannot be repeated consistently. A novel but controversial hypothesis postulates that stringent levels of environmental and biotic standardization in experimental studies reduce reproducibility by amplifying the impacts of laboratory-specific environmental factors not accounted for in study designs. A corollary to this hypothesis is that a deliberate introduction of controlled systematic variability (CSV) in experimental designs may lead to increased reproducibility. To test this hypothesis, we had 14 European laboratories run a simple microcosm experiment using grass (Brachypodium distachyon L.) monocultures and grass and legume (Medicago truncatula Gaertn.) mixtures. Each laboratory introduced environmental and genotypic CSV within and among replicated microcosms established in either growth chambers (with stringent control of environmental conditions) or glasshouses (with more variable environmental conditions). The introduction of genotypic CSV led to 18% lower among-laboratory variability in growth chambers, indicating increased reproducibility, but had no significant effect in glasshouses where reproducibility was generally lower. Environmental CSV had little effect on reproducibility. Although there are multiple causes for the 'reproducibility crisis', deliberately including genetic variability may be a simple solution for increasing the reproducibility of ecological studies performed under stringently controlled environmental conditions.

Agroécologie AgroSup Dijon Institut National de la Recherche Agronomique Université Bourgogne Franche Comté Dijon France

Centre d'Ecologie Fonctionnelle et Evolutive Centre National de la Recherche Scientifique Unité Mixte de Recherche 5175 Université de Montpellier Université Paul Valéry École Pratique des Hautes Études Montpellier France

Cluster of Excellence on Plant Sciences Terrestrial Ecology Group Institute for Zoology University of Cologne Cologne Germany

Département de Biologie Ecole Normale Supérieure Université de recherche Paris Sciences and Lettres Research University Centre National de la Recherche Scientifique Unité Mixte de Service 3194 Saint Pierre lès Nemours France

Department of Agricultural Forest and Food Sciences University of Turin Grugliasco Italy

Department of Geobotany Faculty of Biology University of Freiburg Freiburg Germany

Department of Soil and Water Systems University of Idaho Moscow ID USA

Ecotron Centre National de la Recherche Scientifique Campus Baillarguet Montferrier sur Lez France

Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Czech Republic

German Centre for Integrative Biodiversity Research Halle Jena Leipzig Leipzig Germany

Harvard Forest Harvard University Petersham MA USA

Institut de l'Ecologie et des Sciences de l'Environnement de Paris Sorbonne Universités Paris France

Institut de l'Ecologie et des Sciences de l'Environnement de Paris Université Paris Est Créteil Créteil France

Institut de Recherche pour le Développement Institut de l'Ecologie et des Sciences de l'Environnement de Paris Université Pierre et Marie Curie Paris France

Institut Jean Pierre Bourgin INRA AgroParisTech Centre National de la Recherche Scientifique Université Paris Saclay Versailles France

Institute of Agricultural Sciences ETH Zurich Zurich Switzerland

Institute of Biology Leipzig University Leipzig Germany

Johann Friedrich Blumenbach Institute for Zoology and Anthropology Georg August University Göttingen Göttingen Germany

Leibniz Centre for Agricultural Landscape Research Institute of Landscape Biogeochemistry Müncheberg Germany

Max Planck Institute for Biogeochemistry Postfach 100164 Jena Germany

School of Agriculture Policy and Development University of Reading Reading UK

Senckenberg Biodiversität und Klima Forschungszentrum Frankfurt Germany

Swiss Federal Research Institute Zürcherstrasse 111 Birmensdorf Switzerland

Tropical Forests and People Research Centre University of the Sunshine Coast Maroochydore DC Queensland Australia

References provided by Crossref.org

A starting guide to root ecology: strengthening ecological concepts and standardising root classification, sampling, processing and trait measurements