Intense solar radiation constrains plant species richness in global grasslands

Authors

Marie Spohn, Sveriges lantbruksuniversitet
Carlos Alberto Arnillas, University of Toronto
Jonathan D. Bakker, College of the Environment
Elizabeth T. Borer, University of Minnesota Twin Cities
Kari Anne Bråthen, UiT Norges Arktiske Universitet
Marc W. Cadotte, University of Toronto
Erika I. Hersch-Green, Michigan Technological University
et al.

Document Type

Article

Publication Date

2-5-2026

Department

Department of Biological Sciences

Abstract

The search for predictors of plant diversity has challenged scientists for decades. Here we identify intense photosynthetically active radiation (PAR) as a major factor constraining plant species richness in global grasslands. We show that the strength of the negative relationship between species richness and PAR increases with increasing elevation and that species richness is more strongly correlated with intense PAR than with UV-B radiation, climate variables, and atmospheric nitrogen deposition. In addition to species richness, plant biomass was also negatively correlated with PAR at higher elevations, indicating that intense PAR also constrains plant biomass in montane grasslands. Furthermore, we show that the decrease in plant species richness with increasing PAR is mainly caused by a decrease in species richness of forbs, sedges, and rushes. In contrast, species richness of grasses was only negatively correlated with PAR at high elevations, and species richness of legumes was not significantly correlated with PAR. Our results suggest that PAR constrains plant species richness in global grasslands and limits the extent to which plant species of specific functional groups can migrate uphill in response to climate warming.

Publisher's Statement

Copyright © 2026 the Author(s). Published by PNAS. Publisher’s version of record: https://doi.org/10.1073/pnas.2527128123

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Recommended Citation

Spohn, M., Arnillas, C., Bakker, J., Borer, E., Bråthen, K., Cadotte, M., Hersch-Green, E., & et al. (2026). Intense solar radiation constrains plant species richness in global grasslands. Proceedings of the National Academy of Sciences of the United States of America, 123(6). http://doi.org/10.1073/pnas.2527128123
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/2382

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.

Version

Publisher's PDF