Corsica

The high-altitude forests of Corsica are considered living laboratories for how old-growth ecosystems will respond to climate change.

Our aim on this expedition was to begin to decode how the oldest trees in the Mediterranean partner with fungi to survive extreme climate stresses. In recent years, these old-growth ecosystems have faced the most extreme effects of a rapidly warming climate: extreme droughts are increasing, "high fire risk" days are projected to double, and the island’s soils are eroding faster than nearly anywhere else in Europe. 

Led by Dr. Aurélie Deveau (INRAE), Dr. Francis Martin (INRAE), Dr. Nicolas Suberbielle (CBNC), Dr. Jean-Paul Maurice (affiliation), Dr. Merlin Sheldrake (VU, SPUN) and Dr. Toby Kiers (VU, SPUN), the expedition team spearheaded an emerging technique called metatranscriptomics that uses the information encoded in fungal RNA to understand the function and activity of fungal genes underground at exact moments in time.

The team constructed elevational transects across the island to cover forests of different ages and a variety of climate extremes. To preserve the RNA of living fungal networks, the team needed to carefully sample under the roots of the old-growth trees and instantly freeze the samples on dry ice to prevent the unstable RNA molecules from degrading in the hot weather. 

These fungal samples will allow us to decode what genes are upregulated and downregulated in the fungal RNA during heat stress. This information will be crucial to understanding how fungal networks help old-growth forests survive climate extremes.

The fungi of Corsica are particularly interesting  because they are thought to have unique "enzymatic" capabilities that allow them to break down rock and access nutrients which they feed to trees – features seen primarily in old-growth forests. Black pine forests and their fungi are also thought to be critical in protecting against erosion.