ForestGEO scientists assessed multiple tree-level conditions across six tropical forests to provide a ranking of importance of tree mortality risks.
The rate at which trees are dying is increasing worldwide. Yet, little is known about what kills trees in natural forests. This is particularly difficult to study in diverse tropical forests, where species vary widely in their responses to different conditions. Forest ecologists assessed trees of 1,900 species in six tropical forests to provide the first ranking of importance of mortality risk factors. Among 19 mortality risk factors evaluated, researchers found that those related to tree-level damage were the dominant risks associated with tree mortality.
This study provides the basis to prioritize next-generation experiments on tropical tree mortality. Future research should focus on the links between damage related risks, their climatic drivers, and the physiological processes to enable mechanistic predictions of tree mortality.
Carbon losses due to tree mortality in tropical forests constitute a significant source of uncertainty in vegetation models. Yet, the relative importance of mortality risk factors remains poorly understood. In this study, researchers recorded data on a broad suite of observations of living trees and monitor their subsequent survival to provide a ranking of importance of tree mortality risk factors in tropical forests. The researchers presented a new framework for quantifying the importance of mortality risk factors and applied it to compare 19 risks on 31 203 trees (1977 species) in 14 one-year periods in six tropical forests. They found that factors related to tree-level damage such as crown loss or trunk loss were the most impactful in terms of their contribution to total mortality. Leaning, defoliation and lower elevation ranked next in importance, whereas other risks expected to be important such as those associated with lianas, stranglers, trunk deformities and trunk rot were not impactful in this study. This ranking should inform research priorities and model experiments to improve predictions of the fate of forests in global dynamic vegetation models.
Features. This study was highlighted by Nature Plants in their “Year in Review.” The feature can be found by following this link.
This project and DZ were supported as part of the Next Generation Ecosystem Experiments-Tropics, funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research. Data collection was supported by the Forest Global Earth Observatory (ForestGEO) of the Smithsonian Institution.
Zuleta, D., Arellano, G., Muller-Landau, H.C., McMahon, S.M., Aguilar, S., Bunyavejchewin, S., Cárdenas, D., Chang-Yang, C.-H., Duque, A., Mitre, D., Nasardin, M., Pérez, R., Sun, I.-F., Yao, T.L. and Davies, S.J. “Individual tree damage dominates mortality risk factors across six tropical forests.” New Phytologist (2021). [DOI: 10.1111/nph.17832]