Researching the unacknowledged: A young Belgian researcher’s journey to understand the hidden world of forest soils
By Rina Tsubaki.
Soil might not be the first thing you notice when walking through a nearby forest. But it’s a quiet, hidden guardian that our forests depend on. It connects trees, insects, and fungi in ways we often overlook. Many soil organisms feed on dead plant residues, making important nutrients available to plants. Additionally, while feeding and digging, they incorporate organic carbon into the soil, improving soil structure and water holding capacity. Healthy, biodiverse soil is therefore essential for making forests resilient and multifunctional and cannot be ignored by anyone working in sustainable forest management.
Yannick De Win, a young researcher at Belgium’s Research Institute for Nature and Forest (INBO), is putting his heart into this very topic through two EU-funded projects: INFORMA and WILDCARD. Each tackles a different but connected question: one asks how humans should actively manage forests, while the other explores to what extent rewilded forests can contribute to carbon capture and soil biodiversity. Through his work, Yannick has helped us navigate the hidden power of soils and their role in shaping forests that can endure climate impacts.
How did you end up researching forest soil? Which aspects spark your interest?
As a child, I loved forest walks with my grandparents during the summer and watching nature documentaries. These early experiences sparked my interest in nature and, subconsciously, guided me to where I am today. The idea of studying bioscience engineering came to me when I was sixteen, and pursuing a university degree in this field was a logical choice, as it provides a strong foundation in biology, chemistry, physics, and mathematics. During the study, I realised I really enjoyed learning about nature and forestry. When it comes to understanding a forest’s functioning, all these sciences for sure come in handy. Now, thanks to my job at INBO, I even got the chance to pursue a PhD at KU Leuven.
It is always important to keep in mind that nothing in a forest stands alone. When you look at a specific process, you always have to keep all other mechanisms in mind. Although we walk on it every day, there is still so much to be discovered about the ground below our feet. During my master’s thesis, I studied how forest management influenced the microclimatic conditions on the forest floor, thereby impacting soil biodiversity. It really made me realise how everything in the forest is interconnected.
Brabantse Wouden, one of INFORMA’s case study areas in Belgium, is among the oldest forests in the country, covering over 10,000 hectares of Atlantic beech and oak, mixed with pines and maples. Both societal and ecological expectations are high in these forests. On one hand, people value the aesthetic beauty of the landscape, which attracts visitors and hikers to areas like Hallerbos, a famous tourist destination for the urban population in spring, for its carpets of bluebells. On the other hand, these forests are crucial habitats for species such as the honey buzzard, middle-spotted and black woodpeckers, and various types of bats. At the heart of it all is the soil, which connects and sustains the entire forest ecosystem.
What did you learn from studying soil? What is something surprising that people may not know?
I already talked about how everything is interconnected, which is really cool to think about. However, what surprised me the most was how many different species live in the soil. For example, we see mushrooms, but there is a whole hidden network of fungi forming different associations with trees and connecting them in the forest, helping them take up nutrients and water, and even letting them communicate with each other. We also know what an earthworm looks like, but there are many different kinds of worms living in different depths and performing various functions. And then there are so many other organisms we don’t even think of, like springtails, mites and bacteria. With the environmental DNA (eDNA) analyses in WILDCARD, I hope we will find rare or even new species, even though that would make my work more challenging.
Through WILDCARD, Yannick has been collecting soil samples to measure belowground carbon and the organisms living in unmanaged forests. The project has an impressively wide reach: out of over 500 unmanaged forest sites across 16 European countries, Yannick’s team has coordinated the collection of samples from 200 sites, of which 15 are in Belgium. Soil samples are collected in Ziplock bags and shipped to INBO for carbon analysis. For eDNA, testing to assess soil biodiversity, the samples are frozen to prevent DNA degradation.
How does the knowledge gained through WILDCARD help you in Brabants Wouden, a Belgian case study area of INFORMA? What are the elements forest management needs to be aware of?
I think most people often underestimate how important soil is to a forest, but also how important a forest is for the soil. Forest managers already are more aware of this. Soil texture and moisture content will influence their decision to plant a certain tree species. They know that the litter of some trees decomposes more slowly than others, acidifying the soil. Forest managers are careful when extracting wood with heavy machinery to avoid soil compaction.
In my research, I primarily focus on unmanaged forests. Here, spontaneous processes without human intervention can thrive, starting from natural regeneration to tree competition to tree death and wood decay. This will influence both carbon storage and biodiversity in the forest. By studying these forests, we can better understand how they behave in the absence of forest management. For example, we expect to see that the amount and variety of dead wood increase the diversity of soil organisms and, more specifically, the species bound to forests. At the same time, decomposing dead wood will increase the amount of carbon stored in the soil over time. There is also growing attention to spontaneous processes and old-growth characteristics in managed forests. Understanding how these processes work can convince managers and the broader public that these aspects are worth preserving. It can also persuade people to stop performing certain activities. For example, creating large gaps in the canopy might be detrimental for drought-sensitive soil organisms.
Yannick is in the second year of his PhD at KU Leuven. When asked about his dream, he shared that he hopes his work will enhance our understanding of European forest soils, support the sustainable management of forests and, where appropriate, inform decisions to set them aside.