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School of Geography

Will Barker Will Barker

Contact details

School of Geography
University of Leeds
University Road
Leeds LS2 9JT   UK



Project title

Do natural enemies constrain nitrogen-fixing tree abundance in tropical rainforests?

Project overview

The potential of tropical rainforests to act as terrestrial carbon sinks is limited by bioavailable soil nitrogen (Vitousek et al., 2013; Huntgate et al., 2003). Tropical nitrogen-fixing trees may be able to increase soil nitrogen via biological nitrogen fixation (BNF) (Batterman et al., 2013) under rising atmospheric CO2, reducing nitrogen limitation (Vitousek et al., 2013). However, nitrogen-fixing trees comprise a small component of tropical forest communities, around 10% of basal area, despite the advantages of the nitrogen fixation trait (Menge and Chazdon, 2016; Menge et al., 2014). Previous studies suggest that preferential targeting by natural enemies, such as herbivores and pathogens, may offset the benefit of nitrogen fixation (Costa et al., 2016, in prep; Kursar and Coley, 1991). This project seeks to understand why nitrogen fixer abundance is constrained in tropical forest, looking at the role of herbivores and pathogens in particular, and to examine how these constraints may change under future climate scenarios.


In this project I will test alternate hypotheses concerning the role herbivory may play in limiting nitrogen fixing tree abundance. These hypotheses include preferential herbivory driving defence trade-offs, or density/distance dependent effects, variations in seed strategy, and a temporal-spatial biogeochemical niche hypothesis. These hypotheses will be tested using factorial herbivore and pathogen exclusion experiments and surveys in the field, in Panama, and by using numerical models. Findings will then be compared to data in the RAINFOR data set, to see if they can be generalized to tropical forest throughout Central and South America. Findings from this project will increase the accuracy of modelling future carbon and nitrogen sequestration in tropical rainforests, and contribute to a greater understanding of tropical ecology and biogeochemical cycles.


Research Affiliations


LARS Scholarship

Short Curriculum Vitae


2012 to 2016 – First Class BSc (Hons) Plant Science with Industrial Experience, The University of Manchester.

Biologically Relevant Work Experience:

2015 – Student Volunteer, Orchid propagation laboratory, University of Manchester:

  • Carried out sowing and replanting of Orchids and fungal isolations under varying experimental conditions. Became familiar with sterile technique.

2014-2015- Research Assistant, Timburi Cocha Research Station, Ecuador:

  • 10 months working as a full time researcher on site.
  • Conducting research into mutualistic interactions in myrmecophytic plants, mammal camera trapping and primate conservation.
  • Facilitating research from multinational universities in the field.
  • Securing positive relations with government bodies, academic staff and local people.