Tropical forest soil microbial carbon dynamics

Background: 

Tropical forests play a dominant role in the terrestrial carbon cycle. They cycle more carbon between the land and the atmosphere than any other terrestrial ecosystem, and contain huge stores of carbon in their plants and soils. However, this vital ecosystem service is under threat in a warming world. Climate warming is predicted to destabilise large stocks of soil carbon in terrestrial ecosystems by increasing rates of decomposition in soil. Consequently, this could significantly accelerate climate change through increased emissions of carbon dioxide to the atmosphere.

Models and experiments performed outside the tropics show that the size of this feedback is strongly affected by the response of microbial communities and their carbon-use. Despite this, we have scarce information on the nature of these responses in tropical forests.

 

Objectives: 

In this PhD project, the student will investigate how microbial carbon-use determines the vulnerability of soil carbon stocks to warming in tropical forests. Microbial carbon-use has a huge influence on soil carbon stabilisation and on the magnitude of carbon release under warming. However, our understanding is limited by lack of critical assessment of the methods used for its quantification.

 

The student will address the following specific research questions: i) How does soil microbial community functioning and metabolism in tropical forests change under warming? ii) Are these changes linear or non-linear across ranges of warming and over time? iii) How are these functional responses related to the composition of the microbial community? iv) How do changes in microbial nitrogen and phosphorus use under warming affect carbon processing? v) How is soil microbial ‘carbon-use efficiency’ related to the isotopic and molecular methods used to describe it? The student will address these questions by using existing soil-warming experiments in lowland and montane tropical forests, laboratory experiments and biogeochemical and stable isotope techniques.

The project provides a timely opportunity to address critical questions on the relationships between soil microbial ecology and biogeochemical cycling in tropical forests. A major strength of the project is the combination of analytical training and expertise in molecular analytical methods at The University of Vienna and the UK Centre for Ecology & Hydrology, and novel experimental study systems in tropical forest (SWELTR, situated at the Smithsonian Tropical Research Institute). The work will deliver new understanding on soil microbial carbon cycle feedbacks on the climate under future global change scenarios.

 

Methods and training: 

The student will employ techniques in biogeochemistry and microbiology and use a soil warming experiment in lowland tropical forest (SWELTR) to deliver novel mechanistic understanding of field warming responses. This study systems will be complemented by laboratory incubation studies to understand the temperature response of microbial carbon-use.

The student will receive comprehensive training at the University of Leeds and UKCEH in biogeochemical analyses including molecular and isotopic methods: ¹³C-substrate utilisation and ¹³C tracing into biomarkers (e.g. phospholipid fatty acids), ¹⁸O labelling followed by DNA extraction, and stoichiometric methods by measurements of microbial biomass, soil elements and enzymes. The field work components, including laboratory facilities for incubation studies, will be hosted by the Smithsonian Tropical Research Institute in Panama. Further isotopic work will be performed at UKCEH using the state-of-the-art isotopic facilities including Picarro CRDMS (Dr J. Whitaker) and at the University of Vienna (Dr W. Wanek). Training in generic transferable and professional skills will also be provided by The University of Leeds.

Requirements: 

The successful candidate will have a Masters Degree or equivalent. The candidate will demonstrate interest or research in fundamental ecological and biogeochemical questions. In addition, the candidate will have a background in the natural sciences (biological or Earth), especially biogeochemistry, ecology, molecular sciences and soil science. The successful candidate will have a proficiency in statistical methods (R software), be highly self-motivated and able to work independently, including remote tropical forest fieldwork. Spanish skills are helpful but not essential.

To apply: 

Please follow: https://yes-dtn.ac.uk/application-information/

At the same time please send letter of interest: (heading: “PhD-tropicalC”) with CV to A.Nottingham@leeds.ac.uk

 

 

Relevant publications by the advisory team:

 

Buckeridge, K. M., Creamer, C., & Whitaker, J. (2022). Deconstructing the microbial necromass continuum to inform soil carbon sequestration. Functional Ecology, 36, 1396–1410. https://doi.org/10.1111/1365-2435.14014

Buckeridge, K.M., Mason, K.E., McNamara, N.P. et al. Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization. Commun Earth Environ 1, 36 (2020). https://doi.org/10.1038/s43247-020-00031-4

Liu, X., Tian, Y., Heinzle, J., Salas, E., Kwatcho-Kengdo, S., Borken, W., Schindlbacher, A., & Wanek, W.(2024). Long-term soil warming decreases soil microbial necromass carbon by adversely affecting its production and decomposition. Global Change Biology, 30, e17379. https://doi.org/10.1111/gcb.17379

Nottingham, A.T., Scott, J.J., Saltonstall, K. et al. Microbial diversity declines in warmed tropical soil and respiration rise exceed predictions as communities adapt. Nat Microbiol7, 1650–1660 (2022). https://doi.org/10.1038/s41564-022-01200-1

Nottingham, A. T., Gloor, E., Bååth, E., & Meir, P. (2022). Soil carbon and microbes in the warming tropics. Functional Ecology, 36, 1338–1354. https://doi.org/10.1111/1365-2435.14050

Nottingham, A.T., Meir, P., Velasquez, E. et al. Soil carbon loss by experimental warming in a tropical forest. Nature 584, 234–237 (2020). https://doi.org/10.1038/s41586-020-2566-4

Tian, Y., Shi, C., Malo, C.U. et al. Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses. Nat Commun 14, 864 (2023). https://doi.org/10.1038/s41467-023-36527-8