Hi,
I am Océane, I arrived in the Soil Ecosystem lab 2 years ago to work on this project as a postdoc. I did my PhD thesis on plant/microbe interactions in a small city called Nancy, located in the North East of France.
I studied a beech tree forest, where, despite a natural pH and nutrient gradient, tree productivity was surprisingly even across the site. While studies evidencing the role of microorganisms in tree health and productivity were accumulating, I investigated the role of mineral weathering bacteria located in the rhizosphere of beech trees in this process. I found out that beech trees recruited efficient mineral weathering bacteria in their rhizosphere, thus increasing the availability of inorganic nutrients, exclusively in nutrient-poor soils. Meanwhile, no enrichment was observed in the bulk soil. This study permitted us to dig deeper into the mechanisms of recruitment of a specific rhizosphere microbiome by trees, depending on surrounding environmental conditions, in particular those which can induce stress. During this period, I specialized in classic microbiology, made several bacterial collections and tested their functions. I also started studying molecular microbial ecology to unravel the structure of microbial communities in forest soils. This project gave me an insight into the functioning of academia, the publication process, and inspired my interest in R and statistics more generally. Plus, I discovered a new hobby of making nice plots.
Although this period was really enriching for me and I really enjoyed the labwork, fieldwork in the forest and the computing work, I found it a little frustrating to not be able to extrapolate my results to other sites. I ended up realizing that in science, the more we know, the more we can apprehend how much we don’t know. After this experience, I wanted to be part of a broader project, where I could observe microbial communities on a larger scale, on more samples, to be able to draw big trends of microbial distribution. I was also expecting to sharpen my bioinformatic and modelling skills with a new project.
This is how I ended up at the University of Manchester, working on a fascinating project designed by Franciska, with Chris, Carolin, Holly, Rob and Tim, on a subject that really matters to me. Instead of talking about global warming, now most of us know that we should talk about “global change”. We’re not only expecting a rise of average temperatures, but also an increase in the frequency and intensity of extreme climatic events, such as hurricanes, drought, heat waves, flooding or freezing. The past few decades have shed light on the role of soil microorganisms in several soil ecosystem functions, like biochemical cycles, nutrient recycling, and organic matter decomposition. While an annual change in climate could alter microbial communities progressively, extreme climatic events can abruptly disrupt microbial communities, with unknown consequences on their long-term resilience and on ecosystem functioning. The main threat is a loss of soil biodiversity, resulting in a reduced soil multifunctionality and a loss of ecosystem services such as soil fertility and plant productivity. However, predicting soil microbial community response to extreme climatic events is difficult as it depends on several parameters interacting with each other, like soil properties (pH, moisture, nutrient availability), plant coverage (diversity, community composition) and climate history. This project aims to unravel the factors driving soil microbial response to extreme climate events through three experiments, with a focus on a different aspect for each (see figure):
1. Thirty natural grassland sites across on a European gradient, where soil type/climate/plant community vary (many confounding factors but many sites)
2. An experimental site (Raindrop) where climate has been manipulated for four years (rainfall addition/exclusion) but soil type/plant community are constant
3. A mesocosm experiment where plant communities had been manipulated to obtain a gradient of functional traits, where soil type/climate are constant
For those three experiments, the soil samples collected were subjected to several disturbances in the lab (drought/flooding/heating/freezing) to observe the response of soil microbial communities. In particular, the aim was to identify the response and effect traits related to the resistance and resilience of microbial communities.
At this stage, experiments 1 and 2 have been set-up and harvested and I’m modelling the response of soil microbial communities and soil functions. Experiment 3 has recently been set-up just before the shutdown of the country by Holly and we’re currently expecting to harvest in August/September. Hopefully, those experiments will allow us to have a better understanding on the factors driving microbial resistance and resilience to extreme climatic events.
Stay tuned if you want to know more about this project!
Microbial response to extreme climatic events 