The world’s oldest trees protect hidden underground ecosystems
spun authors
summary
Ancient giant trees host exceptionally rich fungal communities beneath the soil. Protecting millennial trees may therefore safeguard hidden biodiversity essential for forest resilience and regeneration.
Ancient, large-diameter trees are biodiversity hotspots not only aboveground, but also beneath the soil. Protecting millennial trees helps preserve the hidden fungal networks that sustain healthy forest ecosystems.
Some of the world’s oldest trees may also support some of the richest underground fungal communities. This study examined soils beneath giant Alerce trees in the temperate rainforests of southern Chile, including the famous “Alerce Abuelo,” a tree thought to be thousands of years old.
Researchers found that soils beneath these huge trees contained far more fungal species than soils beneath smaller trees. Many of these fungi were unique to the oldest trees and included important mycorrhizal fungi that help plants absorb nutrients and survive in poor soils. The study also showed that low-phosphorus soils supported especially high fungal diversity.
The findings suggest that ancient trees act like underground biodiversity hubs. Protecting old-growth forests may therefore be critical not just for preserving trees themselves, but also for conserving the hidden fungal networks that keep forests healthy and resilient.
Large and ancient trees are known to play outsized roles in forest ecosystems by storing carbon, regulating water and nutrient cycles, and supporting biodiversity. However, much less is known about how these monumental trees influence soil fungal communities, especially in forests dominated by arbuscular mycorrhizal (AM) fungi rather than ectomycorrhizal fungi.
This study focused on the temperate rainforests of southern Chile, home to Fitzroya cupressoides (“Alerce”), including the famous Alerce Abuelo, one of the oldest living trees on Earth. The researchers investigated whether large-diameter and millennial trees disproportionately support fungal diversity belowground.
The study aimed to:
- Determine whether tree size and age influence soil fungal diversity.
- Assess how fungal community composition changes beneath saplings, medium trees, and giant old-growth trees.
- Examine how soil properties, especially phosphorus availability, shape fungal diversity.
- Evaluate the conservation importance of millennial Alerce trees for belowground biodiversity.
The study found that large-diameter trees strongly increased fungal diversity:
- Soil beneath the ancient Alerce Abuelo tree contained fungal richness up to 2.26 times higher than average samples.
- AM fungal richness beneath Alerce Abuelo was up to 1.75 times higher than average.
- Soil and AM fungal richness positively correlated with:
- Tree diameter (DBH),
- Biomass, and
- Tree height.
The researchers also identified:
- 361 fungal OTUs unique to Alerce Abuelo soils, suggesting millennial trees harbor highly specialized fungal communities.
- Soil phosphorus availability was one of the strongest predictors of fungal diversity and community composition:
- Lower phosphorus levels were associated with higher AM fungal richness.
Overall, the findings showed that giant old-growth trees act as “umbrella species” for conserving belowground biodiversity.
