Study reveals that ancient larch trees in Chile host enormous underground biodiversity of fungi

The temperate rainforests of Chiles Coastal Range are home to a spectacular variety of life: iridescent blue lizards, small wild cats, and curly vines of waxy red bells. Above this biodiversity rise ancient conifers in danger of extinction, called larches (Fitzroya cupressoides), whose trunks can reach the width of a cargo container. These larch forests have exceptionally low mortality and grow slowly; They can live more than 3,600 years. New research published today in the journal Biodiversity and Conservation makes it clear that these enormous trees also host a huge variety of underground organisms that have helped the forest, a huge carbon sink, survive and adapt for millennia. A single large specimen, with an estimated age of more than 2,400 years, harbors more than twice the underground fungal diversity of smaller, younger trees of the same species. The larger the larch, the greater the variety of fungi that scientists found hidden in the soil, including hundreds of species likely new to science. The discovery is important because these soil fungi, known as mycorrhizal fungi, contribute to the functioning of forests. They transport water and nutrients to trees through their root systems and help plants combat stressors such as drought and pathogens. Fungi also act as conduits for carbon uptake into the soil. Globally, communities of arbuscular mycorrhizal fungi — the type associated with larch trees — transport approximately one billion tons of carbon annually to Earths soils. Scientists determined that protecting and conserving old trees will protect hundreds, if not thousands, of species of mycorrhizal and other fungi that inhabit the soils around these giants, each of which plays a role we may not fully understand in keeping these forests healthy and resilient. Not all trees They are the same, and if you remove one ancient tree, the impact on all other species will be greater than if you remove a smaller one, said study co-lead author Dr. Camille Truong, a research scientist at the Royal Botanic Gardens of Victoria and the University of Melbourne in Australia, and a mycorrhizal ecologist at the Society for the Protection of Underground Networks (SPUN). In other words, felling a huge tree can destroy an entire underground community of forest helpers that took thousands of years to come together. And All that diversity means resilience, said Truongs co-lead author Dr. Adriana Corrales, field science director at SPUN. The study arose from an expedition to the Alerce Costero National Park in Chile in 2022, conducted by scientists from Universidad Santo Tomás, Universidad Austral de Chile, Universidad de La Frontera (Chile), Fundación Fungi and SPUN, a nonprofit organization dedicated to the mapping and conservation of mycorrhizal fungal networks throughout the planet. SPUN was co-founded by evolutionary biologist Dr. Toby Kiers. Kiers recently received the Tyler Prize (known as the "Nobel for the Environment") for his work detailing the importance of underground fungal networks in unique ecosystems around the world. Larch, sometimes called Patagonian cypress or lawal in Mapudungun, the language of the indigenous Mapuche people, is the second-longest living tree species on the planet, after the long-lived pine. They are relatives of the North American redwoods, but live even longer. Larch forests are found along the coasts of southern Chile and in the foothills of the Andes, but their distribution was nearly halved over the centuries as the trees were felled for their light, durable wood or burned to make way for grasslands. In fact, the oldest known specimen, which lived 3,622 years, was unfortunately cut down in 1976. And the trees continue to be threatened by changes in land use, climate change and large infrastructure projects. A proposed road would pass just a few hundred meters from larch forests, increasing the threat of fires, tourist pressure and invasive species. So to understand what was at risk and how best to protect the remaining stands, Kiers and other researchers took soil samples from 31 trees, from saplings to the "Grandfather Larch", which is at least 2,400 years old and has a trunk more than 4.5 meters in diameter. They measured the size and biomass of each tree, extracted DNA from the samples, and used genetic markers to identify fungi. Truong analyzed the soil data along with the tree measurements and found that the diversity of fungi in the soil under the largest and oldest specimen was more than 2.25 times greater than in any other sample. These soil samples also included more than 300 fungal species unique to this tree. This is important because the loss of soil fungal diversity "can trigger cascading negative effects on multiple ecosystem functions," the researchers wrote in their paper. These enormous ancient trees act as an “umbrella” that protects the fungal diversity of the soil. Protecting such diversity can contribute to the health of other forest plants.