Assessing the reliability of predicted plant trait distributions at the global scale

Coline C.F. Boonman , Ana Benítez-López , Aafke M. Schipper , Wilfried Thuiller (1) , Madhur Anand , Bruno E.L. Cerabolini , Johannes Hc Cornelissen , Andrés González-Melo , Wesley Hattingh , Pedro Higuchi , Daniel C. Laughlin , Vladimir G. Onipchenko , Joseph Penuelas , Lourens Poorter , Nadejda A. Soudzilovskaia , Mark A.J. Huijbregts , Luca Santini

1 LECA - Laboratoire d'Ecologie Alpine

Abstract Aim: Predictions of plant traits over space and time are increasingly used to improve our understanding of plant community responses to global environmental change. A necessary step forward is to assess the reliability of global trait predictions. In this study, we predict community mean plant traits at the global scale and present a sys- tematic evaluation of their reliability in terms of the accuracy of the models, ecologi- cal realism and various sources of uncertainty. Location: Global. Time period: Present. Major taxa studied: Vascular plants. Methods: We predicted global distributions of community mean specific leaf area, leaf nitrogen concentration, plant height and wood density with an ensemble model- ling approach based on georeferenced, locally measured trait data representative of the plant community. We assessed the predictive performance of the models, the plausibility of predicted trait combinations, the influence of data quality, and the un- certainty across geographical space attributed to spatial extrapolation and diverging model predictions. Results: Ensemble predictions of community mean plant height, specific leaf area and wood density resulted in ecologically plausible trait–environment relationships and trait–trait combinations. Leaf nitrogen concentration, however, could not be predicted reliably. The ensemble approach was better at predicting community trait means than any of the individual modelling techniques, which varied greatly in pre- dictive performance and led to divergent predictions, mostly in African deserts and the Arctic, where predictions were also extrapolated. High data quality (i.e., including intraspecific variability and a representative species sample) increased model perfor- mance by 28%. Main conclusions: Plant community traits can be predicted reliably at the global scale when using an ensemble approach and high-quality data for traits that mostly re- spond to large-scale environmental factors. We recommend applying ensemble fore- casting to account for model uncertainty, using representative trait data, and more routinely assessing the reliability of trait predictions.

Mots clés: ensemble forecasting; environmental filtering; intraspecific trait variation; leaf nitrogen concentration; plant height; specific leaf area; trait–environment relationships; trait model; wood density

Domaines: Sciences de l'environnement; Sciences du Vivant [q-bio]

Coline C.F. Boonman, Ana Benítez-López, Aafke M. Schipper, Wilfried Thuiller, Madhur Anand, et al.. Assessing the reliability of predicted plant trait distributions at the global scale. Global Ecology and Biogeography, 2020, 29 (6), pp.1034-1051. ⟨10.1111/geb.13086⟩. ⟨hal-02960113⟩