Patterns in Root:Shoot Ratios in Tropical Forests Across the Globe

Identifying climatic and ecological controls on a critical—but understudied—ecosystem carbon stock.

The Science

A meta-analysis was conducted to identify the main drivers of root:shoot biomass ratios in tropical ecosystems worldwide. Mean annual precipitation and forest age were the best predictors of root:shoot ratios in the tropical forest biome.

The Impact

Although root biomass is a critical component of an ecosystem’s carbon stock, it is very difficult to measure, especially in tropical forests where plant biomass reaches its maximum. Therefore, the relationships uncovered by this meta-analysis will be extremely useful for predicting total plant carbon stocks in tropical forests across the globe, especially in those systems where root excavation is not feasible.

Summary

Plant biomass reaches its maximum in the tropical forest biome, but a critical component of this pool—root biomass—has rarely been quantified. Some 195 observations of root:shoot ratios in forested tropical ecosystems were collected from multiple independent databases and synthesized in a meta-analysis to identify potential controls on the magnitude of belowground root stocks. Root:shoot ratios were found to be larger in drier tropical forests, in older stands, and in unmanaged forests versus plantations. These data can help constrain the magnitude of the root biomass stock across tropical forests and provide an important roadmap for future empirical studies focusing on root biomass distributions at a global scale.

Principal Investigator

Jennifer Powers
University of Minnesota
powers@umn.edu

Program Manager

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

Funding

The Terrestrial Ecosystem Science (TES) program of the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, award number DESC0014363.

References

Waring, B.G., and J. S. Powers. "Overlooking what is underground: Root:shoot ratios and coarse root allometric equations for tropical forests". Forest Ecology and Management 385 10–15  (2017). https://doi.org/10.1016/j.foreco.2016.11.007.