Flames to Flow

Fire doesn’t end in the forest: what burns in the soil can flow into water. From flames to flow, this project explores how fire severity shapes these hidden connections.

“Flames to Flow – How does fire severity shape soil-water organic matter pathways in boreal forests?” (2026-2027) is a doctoral research project led by Mathilde Rebiffé and funded by the Finnish Cultural Foundation’s North Karelia Regional Fund.

Fire is both a natural disturbance and an increasingly used tool for restoring boreal forests across Finland. North Karelia’s forests are increasingly managed with prescribed burning to restore fire-adapted ecosystems for biodiversity conservation after decades of suppression, while wildfires are becoming more frequent and severe under climate change.

Fire is thus both a management tool and a natural driver of soil–water processes in these lake-rich landscapes. Yet we still lack a clear understanding of how fire severity (the degree of environmental change caused by the fire) affects soil organic matter and pyrogenic matter sources and transport pathways through the ecosystem continuum (Fig. 1).

This project investigates how fire severity shapes these processes in boreal forest soils following low-intensity surface fires / prescribed burnings by addressing three key questions: how fire severity alters soil dissolved organic matter and pyrogenic matter dynamics, how it controls their export to freshwater systems, and to what extent laboratory experiments can reproduce field responses.

The work is built on pre- and post-fire datasets from long-term field experiments at prescribed burn sites, conducted in eastern Finland, complemented by laboratory-controlled burns and leaching experiments, to identify the key mechanisms and thresholds at which fire begins to compromise soil and water functions. Analyses will include physicochemical and isotopic approaches, associated with a multi-sensor fire severity assessment method, linking field and laboratory data to produce robust transferable insights.

The results of this project will contribute to strengthening our understanding of shifting fire regimes and their implications on boreal ecosystems and fire-driven biogeochemical processes. The results will also provide not only regionally actionable knowledge to guide sustainable forest management, prescribed burning practices, and freshwater protection in North Karelia, but also transferable insights to boreal forests across Finland and northern Europe.

Figure 1 – water sampling across the ecosystem continuum

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