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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Root and rhizosphere bacterial phosphatase activity varies with tree species and soil phosphorus availability in Puerto Rico tropical forest

Richard J. Norby
Oak Ridge National Laboratory

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10 October 2017

Understanding the role of roots and bacteria in the phosphorus cycle

The Science 
Phosphorus is an important nutrient for plant growth, but its availability is often limited in tropical forests. While most studies focus on either roots or bacteria, scientists from Oak Ridge National Laboratory studied an important enzyme (phosphatase) in both roots and bacteria, showing that phosphatase release varies with tree species and soil phosphorus availability.

The Impact
Earth System Models poorly represent tropical forests in part due to a lack data on both the phosphorus cycle and the belowground processes that influence them. The results can be used to improve how models represent the influence that roots and microbes have on the phosphorus cycle in tropical forests.

Summary
Earth System Models simulate the global carbon cycle to predict how our world responds to and changes with perturbations to the carbon cycle. Tropical forests absorb a large amount of carbon in the atmosphere, which makes it important to understand how they grow and are influenced by environmental factors such as phosphorus. Roots and microbes interact to access nutrients and water from the soil environment. In tropical forests, roots and microbes must release phosphatase, an enzyme that breaks down phosphorus locked into organic material.  Plant growth in future climates may be highly influenced by whether plants can release enough phosphatase to continue growing. Scientists from ORNL studied phosphatase activity in roots and bacteria collected from different tree species and soil phosphorus availabilities in tropical forests of Puerto Rico to better understand phosphatase activity. The influence of roots and bacteria on the phosphorus cycle are not usually included in Earth System Models. The study’s results can be used to help improve Earth System Models.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

Dorothy Koch
SC-23.1
Dorothy.koch@science.doe.gov

(PI Contact)
Richard J. Norby
Oak Ridge National Laboratory
Environmental Sciences Division
Climate Change Science Institute
norbyrj@ornl.gov (865-576-5261)

Funding
This research was supported as part of the Next Generation Ecosystem Experiments — Tropics, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research.

Publications
K. Cabugao; C. Timm; A. Carrell, J. Childs, T. Lu, D. Pelletier, D. Weston, R. Norby (2017), “Root and rhizosphere bacterial phosphatase activity varies with tree species and soil phosphorus availability in Puerto Rico tropical forest.” Frontiers in Plant Science 8:1834 (2017). [doi: 10.3389/fpls.2017.01834].

Related Links
http://ngee-tropics.lbl.gov

Kristine Grace Cabugao, Dr. David J. Weston, and Dr. Richard J. Norby designed the study.

Kristine Grace Cabugao, Joanne Childs, and Dr. Richard J. Norby conducted the field studies.

Kristine Grace Cabugao, Dr. Collin Timm, Dr. Alyssa A. Carrell, Tse-Yuan Lu, Dr. Dale A. Pelletier, and Dr. David J. Weston isolated bacteria, extracted bacterial DNA, and prepared them for sequencing.

Kristine Grace Cabugao, Dr. Collin Timm, Dr. Alyssa A. Carrell, and Dr. David J. Weston analyzed microbial community sequences.

Kristine Grace Cabugao, Dr. Collin Timm and Dr. Alyssa A. Carrell conducted root and microbial enzyme analysis.

Joanne Childs anayzed P content of collected soils.

Kristine Grace Cabugao drafted the manuscript.

Funding source: U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research.

Facility: Oak Ridge National Laboratory

Field site: El Verde Field Station, Puerto Rico

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