July 13, 2021

How Common Trees of Tropical Puerto Rico Get Their Phosphorus

Trade-offs in fine-root traits indicate alternative strategies to acquire phosphorus.

Root trait adjustments among the five tropical trees studied. Spathodea campanulata and Cecropia schreberiana are pioneer species, and Calophyllum calaba, Dacryodes excelsa, and Prestoea montana are non-pioneer species. Specific root length (SRL) is the length of root per gram of root mass, and AM is arbuscular mycorrhizal fungi.

[Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0) from Yaffar, D., et al. “Trade-Offs in Phosphorus Acquisition Strategies of Five Common Tree Species in a Tropical Forest of Puerto Rico.” Frontiers in Forests and Global Change 4, 698191 (2021). DOI: 10.3389/ffgc.2021.698191]

The Science

This study measured a combination of root traits for acquiring soil phosphorus from five tropical tree species before and after two hurricanes in Puerto Rico. Pioneer tree species had a strategy of high phosphatase activity and fungal colonization, whereas species with a non-pioneer life history strategy relied on high root branching to explore the soil. There was no change in root trait strategies after the hurricanes, but root phosphatase activity decreased.

The Impact

How plants adjust their root traits to better obtain nutrients is relevant for understanding their distribution and can help predict their response to future climate scenarios. Most root trait adjustments are either overly generalized or unrepresented in predictive models, and tropical plants are less studied than temperate plants. This study highlights negative relationships between root architectural and physiological/symbiotic traits, and differences between pioneer and non-pioneer tree species in relationship to their root strategies to acquire phosphorus. No change in most root traits after hurricanes shows the stability of nutrient acquisition strategies. These results can help better understand root adjustments of some tropical trees under soils with low phosphorus availability.

Summary

Trees have the ability to adjust their root traits to better obtain soil phosphorus. For example, they can adjust structural traits like root length or root branching, or physiological and symbiotic traits like root phosphatase activity and mycorrhizal colonization. It is still not clear which combination of adjustments tropical trees might use to better obtain soil phosphorus. This study measured seven root traits of five common tropical trees in Puerto Rico to describe their trait adjustments, as well as their changes after the forest was impacted by two hurricanes. Roots with high colonization of fungi and high phosphatase activity were found to present less branching. This strategy was mostly shown in pioneer trees, while the opposite occurred in non-pioneers. Furthermore, root traits adjustments showed no change before and after the hurricanes, except for root phosphatase activity, which strongly decreased following the hurricanes. These results showed a combination of root trait adjustments for better obtaining soil phosphorus in tropical trees and stability of most root traits adjustments after hurricane disturbances.

Principal Investigator

Daniela Yaffar
Oak Ridge National Laboratory
danielayaffar@gmail.com

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
brian.benscoter@science.doe.gov

Funding

This research was supported as part of the Next Generation Ecosystem Experiments–Tropics (NGEE–Tropics), funded by the U.S. Department of Energy’s (DOE) Office of Science Biological and Environmental Research (BER) Program.

References

Yaffar, D., et al. "Trade-Offs in Phosphorus Acquisition Strategies of Five Common Tree Species in a Tropical Forest of Puerto Rico." Frontiers in Forests and Global Change 4 698191 (2021). https://doi.org/10.3389/ffgc.2021.698191.