Underground life forms in forests, often unseen, that are consumed by fire
In the heart of our planet's ecosystems, forests play a vital role in sustaining life, including our own. A renowned expert in Forest Engineering, Forest Biotechnology, and scientific communication, Dr. Jaime Olaizola, sheds light on the intricate relationship between forests and the microorganisms that inhabit their soil.
The health of a forest is intrinsically linked to our own wellbeing. Beneath the surface of the forest floor, a world teems with life—the forest's microbiota. This microbiota, composed of fungi and other microorganisms, plays a crucial role in sustaining biodiversity and enabling ecosystem recovery after fires.
After a fire, the damage may be invisible to the eye, but it contributes more biodiversity than the plants or animals we see on the surface. The microbiota, particularly the soil microbiota, decomposes organic matter, cycles nutrients, retains soil carbon, and supports plant symbioses such as arbuscular mycorrhizal (AM) fungi.
Techniques to restore soil microbiota after disturbances like wildfire include re-establishing diverse vegetation, hydromulching, erosion control measures, and using microbial inoculants to enhance beneficial fungal and bacterial communities. Diverse and living plant cover above soil supports microbial biomass and diversity, enhancing fungal richness and assisting plant nutrient uptake and pathogen resistance.
Legumes, in particular, are effective in this regard. They increase nitrogen availability, boosting microbial community function and AM fungal colonization potential, which benefits subsequent plant growth cycles. After fires, high-intensity heat can destroy soil organic matter and microbial communities, increase erosion, and create hydrophobic soil layers; recovery can take 5–15 years if untreated. Emergency restoration treatments such as hydromulching with native grass species and erosion control structures are applied to stabilize soils and foster microbial and plant community recovery.
Biological restoration, therefore, focuses on reintegrating diverse and functional plant communities to restore soil microbiota, which underpins forest ecosystem resilience and biodiversity. Research highlights the importance of plant diversity and legume presence to enhance soil microbial diversity and health, which then facilitates nutrient cycling and forest regeneration post-fire. Monitoring and testing soil conditions help guide appropriate restoration interventions, including applying microbial inoculants or organic amendments when needed.
Advances in technology and biotechnology have made it possible to perform genetic analyses to see all the microorganisms in the soil. This knowledge can be harnessed to develop customized inoculations for soil recovery, a practice already common in agriculture, particularly in countries like China, India, the United States, Brazil, and Russia.
Moreover, the forest's microbiota functions similarly to the microbiota in humans. Just as our bodies host thousands of species and thousands of microorganisms, some even unknown, so too does the forest. Without these microorganisms, 20% of young trees would be condemned to die in the first year.
The solution to recover the forest's microbiota lies in the soil itself. Using mycorrhizal plants in reforestation or including beneficial microorganisms in the hole where the young tree is planted can help restore the forest's microbiota. Fire can destroy the forest's microbiota along with trees and vegetation, but with careful restoration efforts, we can help our forests thrive once more.
In an exciting new step, this practice can be applied to forest repopulation. A forest, after all, is not just the trees above the ground, but also the fungi that are beneath the soil. The most valuable fungi in the market, such as the black truffle and the boletus, can only grow near a healthy tree. By nurturing the forest's microbiota, we not only help our forests recover but also contribute to the preservation of these valuable species.
References:
[1] Shrestha et al., 2025, Effects of diverse undersown cover crops on soil microbial diversity and health, https://academic.oup.com/femsec/advance-article/doi/10.1093/femsec/fiaf068/8172538
[2] Soil Testing & Wildfire Recovery, Los Angeles, 2025, https://alluvialsoillab.com/blogs/soil-testing/soil-testing-in-los-angeles
- The health of our forests and our own well-being share an intricate relationship, as demonstrated by the microorganisms in the forest's soil.
- The importance of a diverse and healthy microbiota, including fungi and other microorganisms, is paramount in enabling forest recovery after disturbances like wildfires, by decomposing organic matter, cycling nutrients, and supporting plant symbioses.
- Inspired by advances in technologies and biotechnologies, customized inoculations for soil recovery are being developed and have already gained popularity in agriculture, which can potentially be applied to forest repopulation efforts, ensuring the lasting health of forests and preserving valuable fungal species.
