HoliSoils workshop explores climate and management impacts on Mediterranean forest soils
HoliSoils held a workshop in southern France exploring how climate change and forest management affect soil health. Participants visited experimental sites simulating drought and warming, highlighting soil’s central role in forest resilience.
A couple of hours’ drive from Marseille, in the beautiful southeast of France, one of the final HoliSoils practitioner workshops took place. This event was organised in partnership with the Mediterranean Institute of Biodiversity and Marine and Continental Ecology of Aix-Marseille University (IMBE-AMU).
On Tuesday, 14 October, a total of 52 practitioners, researchers, PhD and Master’s students, and other representatives of the public forestry sector gathered for the workshop, which focused on the effects of climate change and forest management practices on forest soils in the mediterranean region.
From the stars to the soil: a unique experimental setting
The first part of the day, organised at the O3HP experimental site, began with a surprising stop at the Haute-Provence Observatory site, a renowned hub for astrophysics research. After learning more about the impressive two-meter diameter telescope and the astronomical observations conducted there, including the discovery of the first exoplanet, the discussions continued in the surrounding Quercus pubescens forests, very common in the region.
However, this Q. pubescens forest has a unique feature: it is equipped with quite special instruments that simulate the effects of climate change. Already facing three months of summer drought annually, these forests are expected, according to IPCC projections, to experience 30% less rainfall and significant warming by the end of the century. At this experimental site, researchers are already simulating future climate conditions. A 300 m² roof above the canopy has been blocking rainfall since 2010, and in spring 2025 they added spirals of electric resistance wires on the soil surface to raise the temperature by +2 °C.
What is the tipping point? That’s exactly what the researchers are aiming to find out.
Visitors also had the chance to explore part of the forest by walking along footbridges, at canopy level or just above the ground. Along the footbridges, various instruments are sometimes installed to take all kinds of measurements, from stem growth and gas exchanges to the release of volatile organic compounds, litter decomposition, and more.
Participants were also very curious about the eco-acoustic monitoring. The site will be indeed equipped soon with sensors that track soil organism activity combined with DNA analysis to study the present biodiversity.
Management practices under the microscope
In the afternoon, the group headed to the HoliSoils experimental site in Saint-Christol d’Albion. Visitors took a long and pleasant walk through this 5-hectare fenced forest stand, which had not been managed for 60 years before the studies began. This site includes several experimental setups to study the effects of different forest management practices on soils, such as thinning gradients, clear-cutting, and the removal of logging residues. The site is also equipped with temperature and humidity sensors that are monitored in real time.
Mathieu Santonja, an associate professor at Aix-Marseille University, explained how he has observed the structure of soil fauna changing dramatically after just one year following a clear-cut. However, they also observed on the site that with thinning up to 28%, soil communities change relatively little.
After spending the day discussing diverse effects on soils — and, for some, getting their hands in the dirt to study their different organic components up close — participants left with a clear takeaway. As Noémie Pousse, a soil scientist at the French National Forest Office, emphasised: “In forest management, the soil is the foundation of everything.”
By Louisa Bouri-Saouter · Photos by Raghav Sharma
Communications trainees at the European Forest Institute (EFI)
