- Estimated to be more than 2,400 years old, one alerce tree in Chile’s Alerce Costero National Park hosts about twice as much fungal diversity underground as younger alerce trees, a team of researchers found.
- The scientists found 361 fungal DNA sequences unique to this tree, indicating that older trees harbor a vaster fungal network that benefits other plants on the forest floor.
- Real estate expansion, climate change and infrastructure projects continue to threaten the alerce, which is listed as endangered. Although Chile protects the species, experts say older trees that support complex ecosystems should enjoy higher levels of protection and limited interaction from humans.
In an isolated valley within Alerce Costero National Park in southern Chile, one tree towers above all others. At 30 meters (100 feet) high, this alerce abuelo or grandpa alerce, is estimated to be more than 2,400 years old. Its massive trunk and branches are covered in lichens, mosses and even other woody plant species that take root in the crevices of its bark. But beneath it, hidden underground, lies another hidden treasure: a community of fungi known as arbuscular mycorrhizae.
These kinds of fungi establish unique partnerships with plants that are fundamental to keeping forests alive. More than 80% of all terrestrial plants are associated with these fungi, which form underground networks, penetrating roots and creating specialized structures called arbuscules that supply nutrients and water to the plant in exchange for carbon and sugars.
Now, for the first time, scientists have sampled and analyzed the fungal community beneath alerce trees (Fitzroya cupressoides) in the Chilean national park, the country’s largest protected area for temperate coastal forests. Their research revealed that the ancient alerce abuelo hosts two and a quarter times more fungal diversity than its smaller, younger counterparts, highlighting the uniqueness of this old tree.
“All the diversity you see above in the tree branches also happens belowground,” says lead author Camille Truong, a mycologist with the Royal Botanic Gardens Victoria and the University of Melbourne in Australia and the study’s lead author. “All these root systems and the soil offer a habitat for thousands of fungi, and also bacteria and insects, forming a whole ecosystem underground.”
The study, published in Biodiversity and Conservation, examined genetic material from fungi found in soil samples collected beneath 31 alerce trees of different ages during a 2022 expedition with scientists from Universidad Santo Tomás, Universidad Austral de Chile, Universidad de La Frontera, Fungi Foundation and SPUN, a nonprofit dedicated to mapping and conserving mycorrhizal fungal networks.
Using a technique called bar coding, the scientists compared short DNA sequences from the samples with genetic reference databases of known species to identify matches or the presence of species still unknown to science. Underneath the alerce abuelo, the researchers identified 361 fungal DNA sequences unique to this tree and absent from other samples, including hundreds that likely belong to new species of fungi not yet described.
“While these may not be exclusive to the old alerce, their presence indicates a greater overall diversity that can also benefit other understory plants in the forest by providing access to a broad mycorrhizal network,” Truong tells Mongabay.
The discovery didn’t come as a surprise, as the researchers expected that older trees would harbor greater fungal diversity due to their larger root systems. But it has helped them confirm the relationship: The larger the tree, the greater the fungal diversity found beneath it.
“Those trees have an enormous need for nutrients, and they would not be able to grow without the mycorrhizae,” Truong notes.
An umbrella for biodiversity
Scientists have observed a link between tree size and fungal communities in various species worldwide, but no research on this topic had been conducted in the Southern Hemisphere until now. However, they still do not fully understand how mycorrhizal fungal communities may contribute to tree growth throughout the lifespan of their host trees.
One theory discussed in the field is that as trees age from seedlings to saplings to mature trees, their requirements for fungal partners evolve, and so does the fungal community supporting them. For example, during periods of drought, the trees might benefit from specific fungi that can supply them with more water, while during rainier periods, the fungal community might change again, creating over time a diverse community of fungi with different characteristics and adaptations.
“Over millennia, old trees accumulate a vast diversity of symbiotic fungi as they adapt to countless environmental changes like droughts and even pathogens,” Truong clarifies.
This symbiotic relationship can be especially important in environments prone to droughts and wildfires, as is the case with the alerce forests. In January, wildfires broke out in Argentina, devastating alerce forests in the UNESCO-listed Los Alerces National Park in Patagonia. As the severity and frequency of wildfires is predicted to increase as a result of climate change, the mycorrhizae become even more important for the tree’s resilience, scientists say.
The same is true for old-growth, millennial trees like the alerce. Truong explains they act as “umbrellas” that support an exceptionally high level of biodiversity and cannot be replaced by any other tree.
“Not all trees are equal,” she says, making the case that when cut, such trees cannot be replaced by planting another one. “Native trees that have been in the forest for thousands of years have way more resources, biodiversity and impact than any tree recently planted.”
César Marín, a fungal ecologist at Santo Tomas University and co-author of the study, also calls for greater protection for the ancient alerce trees. The species is considered endangered, with only around 250,000 ancient alerce trees remaining in the wild. Due to its high-quality, strong wood, the tree was exploited to near extinction during the late 19th century through the 1970s and today is still threatened by fires, deforestation and illegal logging.
Although the species is protected in Chile, where cutting it down is an environmental crime, Marín thinks the old-growth forests and large trees should receive special attention with specific policies to protect them. “There are no legal instruments in Latin America to protect specifically the big and old trees, like we see in the U.S. and Poland, for example,” Marín points out.
The researcher emphasizes that ideally, these ancient trees should be kept more isolated from human contact to preserve the complex ecosystems they support. Currently, visitors can approach and touch the alerce abuelo from a viewing platform. However, according to Marín, Corporación Alerce, a nonprofit organization dedicated to protecting alerce trees in Chile, is taking measures to better safeguard the tree from park visitors by moving the platform farther away.
Growing threats
In Chile, alerce trees also face the challenges of climate change and rampant habitat destruction driven by real estate expansion and illegal logging.
Corporación Alerce has investigated numerous land parcels near the national park and has filed complaints with the state-owned National Forest Corporation. According to them, illegal land subdivisions, mostly for speculative purposes, are occurring in flood-prone areas where alerce trees grow around Puerto Montt, a southern Chilean town known as a gateway to the Andes Mountains.
“These trees are being cut down, buried and their habitat destroyed by the construction of enormous drainage ditches and numerous wide roads,” says ecologist Antonio Lara, an emeritus professor at the Austral University of Chile who dated the alerce abuelo in 1993 and founded Corporación Alerce.
Lara was also one of the main opponents of a Chilean government project to build a highway crossing through the Alerce Costero National Park. The project, which environmentalists said would further threaten the tree, was halted at the end of 2023 following intense scientific and public pressure, including a letter published by Lara and other scientists in the journal Science, alerting to the road’s potential environmental impact on the ancient trees.
Lara and colleagues still fear that the project might be revived under the newly elected right-wing government of President José Antonio Kast. He notes that only a few weeks into the new administration, the Ministry of the Environment has already requested the removal of 43 supreme decrees from the previous governments related to environmental protection, including regulations on clean water, greenhouse gas emissions and the creation of national parks and reserves.
“This road is the greatest threat to the alerce forest today,” Lara says. “It is a permanent threat, and we have to be constantly vigilant. We will not rest until we stop this project for good.”
Banner image: Chile’s Alerce Costero National Park is home to most alerce trees still left in the world. Image courtesy of Tomás Munita.
Citations:
Lee, E., Eo, J., Ka, K., & Eom, A. (2013). Diversity of Arbuscular mycorrhizal fungi and their roles in ecosystems. Mycobiology, 41(3), 121-125. doi:10.5941/myco.2013.41.3.121
Truong, C., Corrales, A., Manley, B., Van Nuland, M. E., Stewart, J. D., Urrutia-Jalabert, R., … Marín, C. (2026). Large-diameter trees disproportionately contribute to soil fungal diversity in a coniferous forest with one of oldest living trees on earth. Biodiversity and Conservation, 35(3). doi:10.1007/s10531-026-03277-0
Lara, A., & Villalba, R. (1993). A 3620-Year temperature record from Fitzroya cupressoides tree rings in southern South America. Science, 260(5111), 1104-1106. doi:10.1126/science.260.5111.1104
Urrutia-Jalabert, R., Barichivich, J., Gutiérrez, Á. G., & Miranda, A. (2023). Chile’s road plans threaten ancient forests. Science, 380(6648), 903-903. doi:10.1126/science.adi0228
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