I want to understand how terrestrial ecosystems from the Tropics to the Arctic will respond to global environmental change. Although tiny, soil microorganisms will play a decisive role in determining the future of these ecosystems. This is because microorganisms fuel global plant productivity by breaking down organic matter, releasing carbon dioxide to the atmosphere and yielding nutrients (such as nitrogen and phosphorus) for plant uptake.   

I am particularly interested in understanding how microorganisms regulate the release of carbon, nitrogen and phosphorus from soil organic matter. This is an important first step in being able to predict the plant-soil interactions and feedbacks which will determine the response of terrestrial ecosystems to changes such as climate warming, drought, elevated atmospheric CO₂, nitrogen deposition….and more.

To date, I have investigated the microbial responses to a variety of global change factors:

• For my PhD research (University of Edinburgh, UK), I assessed the direct and indirect effects of warming on carbon-cycling across a tropical elevation gradient in the Peruvian Andes.
• Since the end of 2016 I have been working as a postdoc in Lund, where I have been pursuing two parallel research tracks: investigating (i) how soil microbes respond to variations in moisture and drying-rewetting events using soils from Texas, Ethiopia, The Netherlands, Belgium, and beyond, and (ii) how shrub-expansion and accelerated nutrient cycling affects carbon and nitrogen cycling in the Subarctic.

I typically use a combination of controlled lab-based experiments in parallel with assessments of soils from field-experiments and natural gradients, and employ a series of radio- and stable-isotope based method in order to resolve how bacterial (³H-leucine and³H-thymidine incorporation) and fungal (¹⁴C-acetate-in-ergosterol) growth drive the processes of carbon and gross nitrogen (¹⁵N pool-dilution) mineralization in soils. For future work, I am keen to add methods to measure gross phosphorus mineralization (³³P pool-dilution) and gross protein depolymerization (¹⁵N pool-dilution) to my tool-box.

Recent work: Carbon and nitrogen cycling in the Subarctic

Climate change is driving shrub-expansion into subarctic tundra, thus dramatically altering the amount and type of plant-inputs to soil. We found that in nitrogen-poor subarctic soils, rhizosphere inputs (simulated with the addition of glucose and alanine) increased gross nitrogen mineralization more than carbon mineralization. This suggested that microbial use of soil organic matter increased in magnitude and shifted to components richer in nitrogen (microbial “nutrient mining”). Interestingly, this microbial “mining” for nitrogen was induced even when a source of labile organic matter including nitrogen was supplied.  Read more about this in our new paper. 

In future projects, I want to investigate how microbial demand for limiting resources affects how microorganisms release nutrients from organic matter, and whether microorganisms “mine” specific components of soil organic matter in order to overcome imbalances in resource availability.

I am always interested in supervising BSc and MSc student projects. You are welcome to contact me to discuss ideas for projects!

For the latest updates, check out my Twitter feed: @LetticeHicks