Linking fine root lifespan to root chemical and morphological traits - a global analysis

Authors: HOU, JIAWEN - Chinese Academy Of Sciences; MCCORMACK, LUKE - Morton Arboretum; REICH, PETER - University Of Minnesota; SUN, TAO - Chinese Academy Of Sciences; PHILLIPS, RICHARD - Indiana University; LAMBERS, HANS - University Of Western Australia; CHEN, HAN Y - Lakehead University; DING, YIYANG - Helsinki University; Comas, Louise; VALVERDE-BARRANTES, OSCAR - Florida International University; SOLLY, EMILY - Helmholtz Centre For Environmental Research; FRESCHET, GREGOIRE - Centre National De La Recherche Scientifique

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2024
Publication Date: 4/12/2024
Citation: Hou, J., McCormack, L.M., Reich, P.B., Sun, T., Phillips, R.P., Lambers, H., Chen, H.H., Ding, Y., Comas, L.H., Valverde-Barrantes, O.J., Solly, E.F., Freschet, G.T. 2024. Linking fine root lifespan to root chemical and morphological traits - a global analysis. Proceedings of the National Academy of Sciences (PNAS). 121(16). Article e2320623121. https://doi.org/10.1073/pnas.2320623121.
DOI: https://doi.org/10.1073/pnas.2320623121

Interpretive Summary: Fine root lifespan is a critical trait related to plant strategies of resource acquisition and defenses. Yet how root lifespan fits with trait networks and tradeoffs among traits is largely uncertain. Here, we compiled the most comprehensive dataset of root lifespan data to date with 98 observations from 79 woody species across 40 sites, and linked root lifespan to other traits to address questions of what governs root lifespan at large spatial scales. We demonstrate that root lifespan not only decreases with plant investment in more metabolically active compounds, but also increases with the plant reliance on symbionts. Although theories linking organ structure and function suggest that root traits should play a role in modulating root lifespan, we found little association between root lifespan and tissue structure. Finally, fine root and leaf lifespan were globally unrelated, except among evergreen species, suggesting contrasting evolutionary selection between leaves and roots facing contrasting environmental influences above versus belowground. At large geographic scales, root lifespan was typically longer at sites with lower mean annual temperature and higher mean annual precipitation. Overall, this synthesis points to new avenues for incorporating root lifespan data in global biogeochemical models and the understanding of ecosystem response to a changing climate.

Technical Abstract: Fine root lifespan is a critical trait associated with contrasting root life strategies of resource acquisition and protection. Yet, its position within the multidimensional ‘root economics space’ synthetizing global root economics strategies is largely uncertain, and it is rarely represented in frameworks integrating plant trait variations. Here, we compiled the most comprehensive dataset of absorptive median root lifespan (MRL) data including 98 observations from 79 woody species using (mini-)rhizotrons across 40 sites, and linked MRL to other plant traits to address questions of the regulators of MRL at large spatial scales. We demonstrate that MRL does not only decrease with plant investment in more metabolically active compounds (root nitrogen), but also increases with the plant reliance on mycorrhizal symbionts (root diameter), thereby redefining current interpretation of the global ‘root economics space’. Although theories linking organ structure and function suggest that root traits should play a role in modulating MRL, we found no correlation between root traits associated to structural defense (root tissue density and specific root length) and MRL. Moreover, fine root and leaf lifespan were globally unrelated, except among evergreen species, suggesting contrasting evolutionary selection between leaves and roots facing contrasting environmental influences above versus belowground. At large geographic scales, MRL was typically longer at sites with lower mean annual temperature and higher mean annual precipitation. Overall, this synthesis uncovered several key ecophysiological covariates and environmental drivers of MRL, highlighting new avenues for accurate parametrization of global biogeochemical models and the understanding of ecosystem response to global climate change.