A team of researchers sampling soil beneath a millennia-old conifer in southern Chile found that a single ancient tree can harbor fungal diversity far exceeding the surrounding forest floor. The study, published on March 3, 2026 in the journal Biodiversity and Conservation, used DNA metabarcoding to catalog more than 300 unique fungal taxa in the root zone of the Alerce Abuelo, a towering Fitzroya cupressoides specimen in Chile’s Coastal Range. The results suggest that the largest, oldest trees in these slow-growing rainforests function as biological reservoirs, concentrating fungal life in ways that smaller or younger trees simply do not.
What the DNA Revealed Beneath the Alerce Abuelo
The research team collected soil samples from multiple points across an alerce forest, including directly beneath the Alerce Abuelo, one of the oldest known living trees on Earth. Using both ITS2 and SSU metabarcoding, two complementary genetic sequencing approaches that target different regions of fungal ribosomal RNA, they built a detailed inventory of the organisms living in the soil. The dual-marker strategy allowed the team to detect not only common decomposer fungi but also rarer mycorrhizal species that form nutrient-exchange partnerships with tree roots.
The standout finding was that fungal richness beneath the Alerce Abuelo measured 2.25 times the mean richness per sample across the study area. That gap is striking because the samples came from the same forest, with similar rainfall, elevation, and canopy cover. The difference was driven by the tree itself, specifically its large diameter and the extensive root network that comes with centuries of growth. Large-diameter trees, the study argues, disproportionately shape soil fungal communities in ways that standard conservation metrics, which tend to focus on aboveground biodiversity, routinely miss.
Beyond sheer species counts, the composition of the fungal community beneath the Alerce Abuelo differed from that of nearby soils. Symbiotic fungi that trade nutrients for carbon from tree roots were more prevalent, while some opportunistic decomposers were relatively less common. That pattern suggests that the ancient tree is not simply sitting atop a random slice of forest soil; it is actively engineering the belowground environment through root exudates, litter inputs, and long-term stability.
How Researchers Identified Hundreds of Fungal Taxa
Cataloging soil fungi is notoriously difficult because most species cannot be cultured in a lab. The 2026 study relied on reference databases to match DNA sequences to known organisms, and the choice of database turned out to matter a great deal. The team compared results from three major platforms: UNITE, the standard for ITS-based fungal identification; MaarjAM, a curated SSU database for arbuscular mycorrhizal fungi; and EUKARYOME, a newer rRNA gene reference system designed to identify all eukaryotes.
EUKARYOME detected more mycorrhizal taxa than either MaarjAM or UNITE alone, according to the study’s pipeline comparison. The reason lies in its architecture: EUKARYOME links SSU, ITS, and LSU sequences into a single framework with standardized annotation and versioning. That linked structure reduces the chance that a sequence falls through the cracks because it matches one gene region but not another. For a forest where arbuscular mycorrhizal fungi help trees absorb phosphorus and other scarce nutrients from thin volcanic soils, accurate identification is not an academic exercise. It determines whether conservationists can pinpoint which fungal partners a threatened tree population actually depends on.
The MaarjAM database, first published in 2010, remains a key tool for tracking global patterns in Glomeromycota, the phylum that includes many arbuscular mycorrhizal fungi. But the alerce study’s results indicate that newer, multi-locus databases can capture diversity that older single-marker systems overlook, particularly in understudied ecosystems like Chile’s Valdivian temperate rainforests. Combining databases, rather than relying on a single one, produced a richer and more taxonomically resolved picture of the underground community.
That methodological lesson extends beyond this one forest. As more conservation projects turn to environmental DNA to guide management decisions, the choice of reference system will shape what species appear to be present, which in turn influences which habitats are prioritized. In the case of the Alerce Abuelo, a more complete reference framework revealed a denser network of symbiotic partners than earlier tools might have shown.
Why Ancient Trees Act as Fungal Hotspots
Most coverage of old-growth forests emphasizes carbon storage, and for good reason: alerce trees grow extremely slowly, locking atmospheric carbon into dense wood over thousands of years. But the fungal dimension adds a layer that carbon accounting alone does not capture. A tree that has been rooted in the same spot for millennia builds up a root network that extends far beyond its canopy drip line (creating a vast underground surface area for fungal colonization). Over time, that network accumulates specialist fungi adapted to local soil chemistry, moisture gradients, and interactions with neighboring plants.
The 2.25-times richness multiplier found beneath the Alerce Abuelo hints at a feedback loop. Greater fungal diversity likely improves the tree’s access to nutrients and water, which in turn supports continued growth and root expansion, which in turn supports more fungi. If that cycle holds, then losing a single ancient tree does not just remove one carbon sink. It collapses a fungal community that may have taken centuries to assemble and that likely supports other plants in the surrounding forest as well.
This is where standard conservation thinking tends to fall short. Protecting old-growth alerce stands is already a legal priority in Chile, where Fitzroya cupressoides is classified as endangered. But protection policies typically focus on preventing logging and fire. They rarely account for the belowground networks that keep the forest functional. A protected tree surrounded by degraded soil, stripped of its fungal partners by compaction, drainage changes, or nearby land clearing, may survive in the short term but lose the biological infrastructure it needs to weather drought or disease.
The new findings also intersect with a broader reassessment of soil biodiversity. Recent work has underscored that enormous quantities of organic matter move into Earth’s soils each year, feeding complex microbial food webs. Ancient trees like the Alerce Abuelo act as stable entry points for that carbon, channeling a portion of it into long-lived fungal networks. Those networks, in turn, influence how much carbon remains stored underground versus returning to the atmosphere.
Mapping Risk to Protect What Remains
Ecologist Toby Kiers of Vrije Universiteit Amsterdam, who helped lead the soil sampling effort, framed the work in explicitly protective terms. Kiers and her colleagues collected soil cores because they wanted to understand what was at risk and how best to safeguard the remaining alerce stands. That language signals a shift from pure discovery science toward applied conservation biology, where mapping invisible networks becomes a prerequisite for designing effective protections.
The team’s approach was spatial as well as taxonomic. By comparing samples taken directly under the Alerce Abuelo, under other large alerces, and in nearby areas with smaller trees, they could visualize how fungal richness and composition changed across the landscape. The resulting maps show clear hotspots radiating from the biggest trunks, suggesting that conserving a handful of giant trees may preserve a disproportionate share of the forest’s fungal diversity.
Yet those hotspots are fragile. Soil compaction from tourism, changes in hydrology from road building, and edge effects from nearby land use can all disrupt fungal networks even when trunks remain standing. Public communication around the project has emphasized that the underground fungal world is as worthy of protection as the towering canopies that draw visitors’ attention. In practice, that could mean expanding buffer zones around the oldest trees, limiting heavy foot traffic in sensitive areas, and monitoring soil conditions as closely as tree health.
For policymakers, the message is that ancient trees function as keystone structures not just for birds and epiphytes, but for entire microbial communities that underpin forest resilience. For scientists, the study underscores the value of combining cutting-edge DNA tools with classic field ecology to reveal how much life can be anchored to a single, irreplaceable organism. And for anyone standing at the base of the Alerce Abuelo, the findings offer a new perspective: beneath the rough bark and massive trunk lies an even larger, largely unseen organismal world, one that future conservation efforts will need to keep firmly in view.
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*This article was researched with the help of AI, with human editors creating the final content.
