Wildfires may disappear from the landscape within weeks, but their hidden effects on the soil can persist for decades. An international research team led by the University of Göttingen, together with partners in Tübingen, Berlin and Chile, has shown how wildfires in humid temperate rainforests and mediterranean woodlands of central Chile lead to very different pathways of soil recovery and ecosystem resilience. The study shows that soil structure and nutrients continue to change for more than a decade after a fire. The results were published in the journal Catena.
The researchers used a "chronosequence" approach – meaning they compared forest soils that had burned at different times in the past. This enabled them to reconstruct how soils change in the years after a fire. In two national parks in Chile, the team sampled soils in a humid temperate Araucaria forest in Nahuelbuta and in a "sclerophyll" woodland – meaning forest characterised by woody plants with small, tough leaves – in La Campana, which has a mediterranean climate with hot, dry summers. Here, "mediterranean" refers to Chile's mediterranean-climate woodlands, which share a similar climate with the Mediterranean. The researchers collected soil cores from the top ten centimetres of the ground in recently burned areas – from forests just two days after a fire – as well as from sites that had burned up to 14 years earlier. They then compared the physical and chemical properties of the soil with nearby forests that had not burned for several decades. "We showed that wildfires do not just burn vegetation but fundamentally reshape the soil – compacting it, redistributing ash and disrupting nutrient cycles long after the flames are gone," says Professor Yakov Kuzyakov at the University of Göttingen.
Their research revealed that wildfires increase soil bulk density by up to 1.2 g/cm³, temporarily raise soil pH because of the additional ash, and alter the balance of key nutrients such as calcium, magnesium, and potassium. While humid temperate forests retained more organic matter, mediterranean woodland soils suffered long-lasting carbon and nitrogen depletion. Soils in mediterranean woodlands showed greater compaction and nutrient loss than those in humid temperate forests, where deep-rooted, fire-adapted trees helped soils recover faster.
"Our findings show that soil recovery is not uniform," explains Jhenkhar Mallikarjun, PhD researcher at the University of Göttingen. "Even after 14 years, mediterranean woodland soils in Chile struggled to regain their pre-fire nutrient balance. In contrast, humid temperate forests began to bounce back more quickly due to resilient vegetation and higher rainfall. This means land managers cannot assume that all forests will recover in the same way after wildfires, especially in drier mediterranean woodlands where soils can stay depleted for many years."
"Understanding how fire affects nutrient recovery helps predict how forests might cope with more frequent wildfires under climate change and reveals the wider consequences for carbon storage, water regulation and forest productivity," says Professor Michaela Dippold at the University of Tübingen. "If we ignore the slow recovery of soils and use the same reforestation and management strategies everywhere, we risk undermining restoration investments and the long-term resilience of ecosystems and the societies that depend on them."
The study was funded by the German Research Foundation (DFG) and Chile's National Agency for Research and Development (ANID).
Original publication: Mallikarjun, J., et al. "Post-fire recovery of temperate and Mediterranean ecosystems: An interplay between fire severity, soil nutrients, and vegetation from early-stage to decadal-scale dynamics." CATENA (2025). DoI: 10.1016/j.catena.2025.109431
