Ancient Chile Alerce Trees Support Hidden Fungal Biodiversity

Some of Earth’s oldest living trees thrive in the temperate rainforests of Chile’s Coast Range. Giant alerce trees have endured for millennia through storms, fires and changing climates.

Scientists have now found that their value extends far beneath the forest floor.

Research from the University of Melbourne reveals that these ancient trees serve as underground hubs of biodiversity, sustaining extensive fungal communities that enable forests to recycle nutrients, retain carbon and cope with environmental stress.

The results indicate that the loss of one millennial tree could also erase a concealed ecosystem that has needed thousands of years to develop.

Hidden fungi beneath giant alerce trees

The research showed that a single enormous alerce, thought to be over 2,400 years old, supported more than double the underground fungal diversity recorded around smaller and younger trees of the same species.

Overall, larger alerce trees had a greater number of fungal species in the soil surrounding them.

The team also concluded that many of the organisms could be new to science. Soil around the roots of an ancient tree contained hundreds of fungal species that are probably undiscovered, in a location few people would consider investigating.

This is not simply an interesting observation, according to the study. A millennial tree is more than aged timber and foliage: it may be a complete living home for below-ground biodiversity assembled over thousands of years.

Why these fungi matter to forests

Among the fungal groups examined were mycorrhizal fungi, which build close relationships with plant roots.

They assist the movement of water and nutrients across root systems, while helping plants manage pressures such as drought and disease. Fungi also contribute to carbon storage by transferring carbon into the soil.

The paper stresses the global significance of arbuscular mycorrhizal fungi, the form linked with alerce. Their communities move roughly one billion tons of carbon each year into Earth’s soils.

This is especially relevant in a forest already recognised as a major carbon sink. It implies that the forest’s capacity to endure over the long term, store carbon and recover after stress could partly rely on the diversity of its underground fungal networks.

The researchers therefore maintain that conserving old trees safeguards much more than the trees alone.

It also preserves hundreds, and perhaps thousands, of fungal species around alerce trees, many with functions that are not yet fully understood.

Removing giants transforms ecosystems

“Not all trees are the same and if you remove a millennial tree, the impact on all the other species is going to be bigger than if you remove a smaller one,” said the co-lead author Camille Truong, a research scientist at the University of Melbourne and the Royal Botanic Gardens Victoria.

Truong’s argument is that the loss involves the underground community as well as the trunk visible above the ground.

Once a huge alerce is gone, an ecosystem of fungal partners and helpers vanishes with it, despite potentially taking centuries or millennia to accumulate in that particular area of soil.

“All that diversity means resilience,” said the study’s co-lead author Adriana Corrales, the Field Science Lead at the Society for the Protection of Underground Networks (SPUN).

Examining soil in an ancient forest

The project started during a 2022 expedition to Alerce Costero National Park in Chile. Researchers collected soil from beneath 31 alerce trees, from saplings through to a celebrated giant called the “Alerce Abuelo.”

The Abuelo is believed to be at least 2,400 years old and has a trunk measuring more than 4.5 metres in diameter. The scientists recorded the size and biomass of every tree, extracted DNA from soil samples and identified fungi using genetic markers.

When Truong compared the soil findings with the tree measurements, a clear pattern emerged.

The largest alerce specimen had more than 2.25 times the fungal diversity detected in any other sample. Its soil also held over 300 fungal species found only around that individual tree.

Such a loss would not be tidy or isolated, the study argues. The researchers wrote that losing soil fungal diversity “can trigger cascading, negative effects on multiple ecosystem functions.”

The biggest alerce trees therefore function as an “umbrella” for fungal diversity in the soil, which may in turn underpin the forest’s wider health.

Alerce forests remain under pressure

After bristlecone pines, alerce are the world’s second-longest-lived tree species. Although related to North American redwoods, they can survive for even longer. In Chile, they occur in coastal mountain ranges and Andean foothills.

Their distribution has shrunk substantially over the centuries. People logged the trees for their light, durable timber, while many forests were burned to create pastureland.

The threats have changed today, but they have not ended. Remaining forests continue to face pressure from land-use change, climate change and major infrastructure developments.

A proposed road, for example, would pass only a few hundred metres from alerce forests, raising the potential risks of fire, invasive species and increased tourist traffic.

Against this backdrop, the findings make the stakes clearer. The threat is not limited to losing rare trees; it includes the loss of an unseen reservoir of underground biodiversity that helps forests stay resilient and functional.

Protecting the oldest alerce trees

The study adds weight to a case conservationists have advanced for years: old-growth forests cannot simply be replaced. A forest made up of younger trees cannot immediately take over the ecological functions performed by ancient individuals.

If one exceptionally large alerce can support hundreds of fungal species found nowhere else, safeguarding the oldest trees also becomes a means of conserving whole underground communities.

Because these fungi affect nutrient movement, resistance to stress and carbon storage in soil, their protection could also strengthen the forest’s ability to withstand future shocks.

The research ultimately highlights that some of a rainforest’s most significant biodiversity is not conspicuous. It is silent, microscopic and beneath people’s feet. For Chile’s giant alerce trees, it may be inseparable from the trees that have survived for millennia.

The study was published in the journal Biodiversity and Conservation.