Facilitating the tropical forest carbon sink: The evolution and function of symbiotic N2 fixation

Lead Research Organisation: University of Leeds
Department Name: Sch of Geography

Abstract

Trees with the ability to access nitrogen fertilizer from the atmosphere (N2 fixers) fill a critical role in supporting tropical forest growth and carbon storage and may become increasingly important as climate changes. Whether N2 fixers will help tropical forests store additional CO2 in the future-thereby offsetting human CO2 emissions-may depend on what controls their function and evolution in ecosystems. To better understand the future role of fixers as climate changes, we can learn by examining how fixers responded to major past global change, deducing why fixers evolved and what factors caused their diversification and spread across forests and other ecosystems. I will address this previously-unposed question using a combination of approaches: 1) establishing a large-scale, long-term fertilization experiment in Panamanian tropical forests to test how nutrients limit forest recovery from disturbance and the ability of N2-fixing trees to facilitate carbon storage; 2) utilizing the largest dataset of fixer prevalence and biodiversity across the Amazon Basin to analyze how nutrients control fixers; 3) combining a recent reconstruction of the evolutionary history (phylogeny) of fixers with a dataset of fixer prevalence and biodiversity across tropical regions globally to determine how nutrients govern the evolution and geographical spread of fixers; and, 4) pairing the fixer phylogeny with a review of ancient geological and climatic events to determine what precipitated the major evolutionary events that led to the modern-day distribution of fixers. This approach is expected to lead a new understanding of the function of fixers throughout earth's history and a better ability to predict how their role may change into the future. New findings will inform policy-makers and the public about the reliability of tropical forests to buffer our CO2 emissions, scientists about the importance of biodiversity and plant function, and practitioners about how to protect and restore ecosystems.

Planned Impact

The research contained within this proposal will produce a number of societal and economic impacts. Determining the role of N2-fixing trees in tropical biogeochemical cycles, both past and present, will help to identify how their functional role will change in the future and how they will support a carbon sink in tropical forests as climate changes. The new information will support public policy making, inform conservation and restoration efforts, improve quality of life and health and impact economic activity.

Decision makers about public policy will benefit from our improved understanding of whether mechanisms exist to facilitate a tropical forest CO2 sink. The proposed research will help to determine whether we can count on N2-fixing trees to supply the nitrogen needed for tropical forests to grow more and store more carbon in response to rising CO2 levels. If we positively identify this mechanism, then scientists will be able to improve predictions about the size of the terrestrial CO2 sink, which will reduce uncertainty about the environmental and social costs of carbon that humans emit. This will in turn help to reduce the uncertainty about setting a price on carbon. In addition, policy-makers will be better informed about the importance of protecting forests and biodiversity, through policies such as REDD+.

The findings will inform conservation and restoration efforts by providing evidence of the role of N2 fixers in forests, including their role in supporting forests from recovery and response to climate change. Conservationists will make improved decisions about what forests to conserve and about the importance of protecting biodiversity and ensuring the presence of N2 fixers. People restoring degraded ecosystems will select species (e.g., particular species of N2 fixers) for a particular environment based on scientific evidence to improve restoration efforts and the quality of the restored habitat.

Human quality of life and health will also be improved because the findings will help us to understand what the future environment will be like with regards to climate change. This could lead to improved social welfare and national security because there will be less uncertainty about what the future climate will be like and what our options are with regards to protecting our future and reducing potential future conflicts.

Finally, this research will have economic impacts because understanding the basic mechanisms of how N2 fixers function within biogeochemical cycles can help improve agricultural production, particularly in developing countries where agricultural practices are currently sub-optimal. By understanding when and why N2-fixing trees bring in additional nitrogen fertilizer from the atmosphere can inform farmers about improving agricultural practices such as through intercropping with N2-fixing trees or crops, and improving agricultural efficiency and minimizing agricultural damage via fertilizer application by rotating crops and using N2 fixers as an alternative source of nitrogen.

Publications

10 25 50
 
Description I have discovered that biodiversity is critical for the functioning of tropical forests because nitrogen-fixing tree species from across the nitrogen fixer phylogeny function in different ways within tropical forests. I have also found that the nature of the relationship between plants and their microbial partners can have large and distinct impacts on the global environment.
Exploitation Route I am in the process of partnering with people to incorporate my findings into climate change models. By incorporating my findings about the evolution of nitrogen fixation, I will help to improve our predictions of how nitrogen fixer evolution affected the global environment in the past, and how it will affect climate and the environment in the future.
Sectors Energy,Environment,Other

 
Description My findings are being utilized in training courses for practitioners who make decisions about land use and the environment in Central and South American tropical forests.
First Year Of Impact 2013
Sector Agriculture, Food and Drink,Environment,Government, Democracy and Justice
Impact Types Societal

 
Description Climate Research Bursary Fund to Barker
Amount £2,000 (GBP)
Organisation University of Leeds 
Sector Academic/University
Country United Kingdom
Start 06/2018 
End 09/2018
 
Description Leeds Anniversary Research Scholarship to Barker
Amount £75,000 (GBP)
Organisation University of Leeds 
Sector Academic/University
Country United Kingdom
Start 10/2016 
End 09/2019
 
Description Leeds-China Scholarship
Amount £60,000 (GBP)
Organisation University of Leeds 
Sector Academic/University
Country United Kingdom
Start 10/2018 
End 09/2021
 
Description STRI short term fellowship to Barker
Amount $4,500 (USD)
Organisation Smithsonian Institution 
Department Smithsonian Tropical Research Institute
Sector Public
Country Panama
Start 10/2017 
End 01/2018
 
Description Society for Experimental Biology to Barker
Amount £500 (GBP)
Organisation Society for Experimental Biology (SEB) 
Sector Learned Society
Country United Kingdom
Start 06/2017 
End 09/2017
 
Title Nitrogen fixation and phosphatase traits in Panamanian trees 
Description This data includes information about nitrogen fixation, phosphatase activity, plant nitrogen and phosphorus demand and soil nitrogen and phosphorus availability of nitrogen-fixing and non-fixing trees from seven species grown in an experimental plantation at the Agua Salud Native Species Plantation, El Giral, Panama (9°12'50.15''N, 79°43'26''W). Data were collected by the Smithsonian Tropical Research Institute and Princeton University and were analysed by the University of Leeds. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Dataset made available to the public 
URL https://catalogue.ceh.ac.uk/documents/3578bae2-4b88-4b2e-93e1-6965dfe1348c
 
Description Collaboration with Ben Hur Marimon and Bia Marimon 
Organisation UNEMAT - Nova Xavantina
Country Brazil 
Sector Academic/University 
PI Contribution Designed research and trained masters students.
Collaborator Contribution Provided facilities, collected data, analyzed data and trained masters students.
Impact collaboration is ongoing
Start Year 2016
 
Description Collaboration with Ben Mills 
Organisation University of Leeds
Department School of Biology
Country United Kingdom 
Sector Academic/University 
PI Contribution I provided a major contribution to identifying the research question, designing the study and writing the manuscript.
Collaborator Contribution Ben Mills provided a major contribution to identifying the research question, designing the study and writing the manuscript. Ben Mills did the modeling.
Impact Manuscript in review at Philosophical Transactions: Mills, B., Batterman, S.A., Field, K. Nutrient acquisition by symbiotic fungi governs Palaeozoic climate transition. This research is interdisciplinary, with Ben Mills coming from earth and environment and modeling, Katie Fields coming from biology, and me coming from geography and ecology.
Start Year 2016
 
Description Collaboration with Efrat Sheffer 
Organisation Hebrew University of Jerusalem
Country Israel 
Sector Academic/University 
PI Contribution I helped to formulate and design the study on evolution of nitrogen fixation strategies across latitudinal gradients. I helped to write the paper.
Collaborator Contribution Efrat Sheffer led the development and analysis of the theoretical model and took the lead on writing the paper (Sheffer, Batterman et al. 2015, Nature Plants).
Impact Sheffer E, Batterman S, Levin S, Hedin L. (2015). Biome-scale nitrogen fixation strategies selected by climatic constraints on nitrogen cycle. Nature Plants, 1 (12), pp. 15182 (Commentary) Houlton, B. Z. NITROGEN FIXATION Fixing evolution in global forests. Nature Plants 1, doi:Artn 15205 10.1038/Nplants.2015.205 (2015). https://www.princeton.edu/main/news/archive/S44/88/96G13/index.xml?section=newsreleases
Start Year 2015
 
Description Collaboration with Joe Wright 
Organisation Smithsonian Institution
Department Smithsonian Tropical Research Institute
Country Panama 
Sector Public 
PI Contribution Leading effort to evaluate how fixation rates across the fixer phylogeny are governed by soil nutrients by collecting data on fixation across the fertilization experiment at the Gigante site, to pair with the new experiment in young forests developed as part of the NERC fellowship
Collaborator Contribution Provided dataset collected over 20 years, access to sites, assistance from field technician, guidance on experimental design
Impact No outputs yet
Start Year 2017
 
Description Collaboration with Joice Ferreira, Erika Berenguer, Jos Barlow, Rodrigo Oliveira 
Organisation Brazilian Agricultural Research Corporation
Country Brazil 
Sector Public 
PI Contribution Developing project, supervision of masters student, training
Collaborator Contribution Data collection, analysis and synthesis
Impact No research outcomes yet
Start Year 2016
 
Description Collaboration with Joice Ferreira, Erika Berenguer, Jos Barlow, Rodrigo Oliveira 
Organisation Lancaster University
Country United Kingdom 
Sector Academic/University 
PI Contribution Developing project, supervision of masters student, training
Collaborator Contribution Data collection, analysis and synthesis
Impact No research outcomes yet
Start Year 2016
 
Description Collaboration with Joice Ferreira, Erika Berenguer, Jos Barlow, Rodrigo Oliveira 
Organisation University of Oxford
Country United Kingdom 
Sector Academic/University 
PI Contribution Developing project, supervision of masters student, training
Collaborator Contribution Data collection, analysis and synthesis
Impact No research outcomes yet
Start Year 2016
 
Description Collaboration with Katie Field 
Organisation University of Leeds
Department Sustainability Service
Country United Kingdom 
Sector Academic/University 
PI Contribution I provided a major contribution to identifying the research question, designing the study and writing the manuscript.
Collaborator Contribution Katie Field provided a major contribution to identifying the research question, designing the study and writing the manuscript. Katie Field provided experimental data.
Impact Manuscript in review at Philosophical Transactions: Mills, B., Batterman, S.A., Field, K. Nutrient acquisition by symbiotic fungi governs Palaeozoic climate transition. This collaboration is multi-disciplinary with Katie Field coming from biology, Ben Mills coming from earth and environment, and me coming from geography and ecology.
Start Year 2016
 
Description Collaboration with Klaus Winter 
Organisation Smithsonian Institution
Department Smithsonian Tropical Research Institute
Country Panama 
Sector Public 
PI Contribution Our team designed and conducted an experiment to evaluate the constraints by herbivory or symbiotic nitrogen fixation
Collaborator Contribution Winter provided guidance in experimental design, conduct and analysis, and the facilities and technician help for the experiment
Impact No outputs yet
Start Year 2017
 
Description Collaboration with Liza Comita and Steve Hubbell 
Organisation University of California, Los Angeles (UCLA)
Country United States 
Sector Academic/University 
PI Contribution My team is leading the analysis of a large dataset collected and maintained by Comita and Hubbell to understand the evolution of fixation in tropical forests and the role of herbivory.
Collaborator Contribution They have provided the data, and Comita has provided code and assistance in the data analysis.
Impact The collaboration is in its early stages, so there are no outputs yet.
Start Year 2017
 
Description Collaboration with Liza Comita and Steve Hubbell 
Organisation Yale University
Country United States 
Sector Academic/University 
PI Contribution My team is leading the analysis of a large dataset collected and maintained by Comita and Hubbell to understand the evolution of fixation in tropical forests and the role of herbivory.
Collaborator Contribution They have provided the data, and Comita has provided code and assistance in the data analysis.
Impact The collaboration is in its early stages, so there are no outputs yet.
Start Year 2017
 
Description Contribution to ELTI course 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Assisted with training course for practitioners and politicians surrounding the importance of tropical forests for the environment and best practices for reforestation. The training course actively engaged students who went on to implement best practice recommendations for reforestation generated from my research into their own reforestation projects and government policy.
Year(s) Of Engagement Activity 2016
 
Description Press release for Nature Plant study 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Our Nature Plant study was highlighted in press releases and the media:

http://blog.pnas.org/2015/12/journal-club-model-shows-why-trees-to-fix-nitrogen-where-they-do-offering-insights-with-big-implications-for-the-biosphere/

https://www.princeton.edu/main/news/archive/S44/88/96G13/index.xml?section=topstories

http://www.nature.com/articles/nplants2015205?WT.feed_name=subjects_plant-symbiosis
Year(s) Of Engagement Activity 2015
URL http://blog.pnas.org/2015/12/journal-club-model-shows-why-trees-to-fix-nitrogen-where-they-do-offeri...
 
Description Public press coverage of Batterman et al 2018 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press release for Ecology Letters study
Year(s) Of Engagement Activity 2018
 
Description Public press coverage of Mills et al 2018 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press coverage (BBC, Guardian, Botany One, etc.) of Mills et al. 2018
Year(s) Of Engagement Activity 2018