Measuring Tree Death and Damage in Tropical Forests

New field protocol enables rapid, repeatable, and inexpensive assessment of tree mortality and damage.

Measuring Tree Death and Damage in Tropical Forests

A goal of this protocol is to characterize the multiple conditions trees have before death to improve predictions of tropical forest mortality.
[Image Credit: Courtesy Daniel Zuleta]

The Science

Although tropical forests play a critical role in the global carbon cycle, there is a high level of uncertainty on how they will respond to ongoing global environmental changes. This uncertainty is partially attributed to the poor representation of tree mortality in vegetation demographic models. To improve the mechanistic inclusion of mortality in vegetation models, researchers designed a standardized field protocol to evaluate tree vigor, biomass loss, and factors likely to be associated with future tree death. Improving tree mortality representation in models is a research priority that will enable more accurate estimates of terrestrial carbon budgets and predictions of future carbon cycle–climate feedbacks.

The Impact

Although tree mortality is key to predicting forest response to global changes, much uncertainty remains regarding its causes and consequences in tropical trees. This study proposes a rapid, repeatable, and inexpensive assessment of individual tree death and damage. A new field protocol minimizes the effort required at each tree, enabling frequent assessments of more trees. A comprehensive assessment of tree damage coupled with the identification of factors associated with tree death will lead to an improved understanding of the causes of tree mortality and estimates of biomass fluxes in tropical forests.

Summary

Tree mortality drives changes in forest structure and dynamics, community composition, and carbon and nutrient cycles. Since tropical forests store a large fraction of terrestrial biomass and tree diversity, improved understanding of changing tree mortality and biomass loss rates is critical. Tropical tree mortality rates have been challenging to estimate due to low background rates of tree death and high spatial and temporal heterogeneity. Furthermore, the causes of mortality remain unclear because many factors may be involved in individual tree death, and the rapid decomposition of wood in the tropics obscures evidence of possible causes of tree mortality. To assess tree mortality in tropical forests, researchers developed a field protocol that focuses on the rapid, repeatable, and inexpensive assessment of individual tree death and damage. They successfully tested the protocol, conducting annual assessments of >62,000 stems in several ForestGEO plots in Asia and the Neotropics. Standardized methods for assessing tree death and biomass loss will advance understanding of the underlying causes and consequences of tree mortality.

Principal Investigator

Daniel Zuleta
Smithsonian Tropical Research Institute
dfzuleta@gmail.com

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This research was supported by ForestGEO as part of the Next-Generation Ecosystem Experiments–Tropics (NGEE-Tropics) project funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research.

Related Links

References

Arellano, G., D. Zuleta, and S. J. Davies. "Tree death and damage: A standardized protocol for frequent surveys in tropical forests". Journal of Vegetation Science 32 (1), e12981  (2021). https://doi.org/10.1111/jvs.12981.