Climate change changes symbioses between trees and fungi


Forest near a fire site in the Apennines in Italy. © Society for the Protection of Underground Networks (SPUN), Seth Carnill

Climate change is also changing the living conditions of trees and fungi – and disrupting the synchronization that has developed over the course of evolution. Researchers have discovered that some trees and their symbiotic fungi may no longer occur in the same area as before. If these natural interactions change, this could also affect the biological diversity of entire ecosystems. However, it is difficult to predict exactly where the tree-fungus symbioses will be permanently disrupted and where new collaborations will form.

Climate change is changing the living conditions for all living things on earth. It is not only us humans who will have to adapt to a warmer earth and leave regions that have become uninhabitable; animals, plants, microorganisms and fungi also face this challenge. While animals can conquer new habitats relatively quickly, migration takes longer for plants. Trees in particular migrate very slowly, as observations in recent years have shown.

Ectomycorrhizal fungus on the forest floor
An ectomycorrhizal fungus on the forest floor in Patagonia, South America. © SPUN, Mateo Barrenengoa

How does global warming affect tree-fungus symbioses?

A research team led by Michael Van Nuland from Stanford University in California has now investigated what consequences this could have on the relationships between trees and other organisms. To do this, they analyzed trees and fungi that currently live together in symbioses and depend on each other. The fungi supply the trees with nutrients via their roots and in return receive carbon from the plants through their metabolism. The biologists sequenced the genetic material of mycorrhizal fungi that live in North American forests from almost 6,000 soil samples. They also evaluated records of the tree populations there. From this data, Van Nuland and his colleagues developed computer models that predict the future distribution of 50 tree species and 400 fungi that have so far entered into partnerships with trees.

According to forecasts, both trees and fungi will grow at higher latitudes in the future as a result of global warming because it will be cooler there than in their previous habitats. Their current distribution areas will therefore shift northwards. The regions in which both trees and fungi can thrive will continue to overlap and even result in larger areas as potential habitats. Previous mycorrhizal symbioses between trees and fungi will therefore still be possible in the future. New partnerships could also arise in this way. The Canadian black poplar, the American white oak, the American hornbeam and the American beech, as well as walnut and beech plants in general, could particularly benefit from new symbiotic partners, as the team reports.

Cortinarius spp., a mycorrhizal fungus
Cortinarius spp., a mycorrhizal fungus. © SPUN/Mateo Barrenengoa

Trees in the north will find fewer fungal partners

However, this positive trend does not apply to all tree-fungus partnerships, as the biologists found. For around 35 percent of today’s mycorrhizal symbionts, climate change will probably mean that there will be less habitat available in which both partners can grow. Symbioses in northern latitudes will be particularly affected. Trees in the north will therefore find it difficult to find fungal cooperation partners in the soil, which in turn will make it more difficult for them to settle in northern, cooler regions, according to Van Nuland and his colleagues. Pine trees such as the rock fir and the lodgepole pine are particularly affected.

According to the biologists, these findings should be taken into account in future environmental and nature conservation measures. In addition, further research must be carried out into how climate change affects mycorrhizal symbioses, says Van Nuland. “These relationships underpin all life on Earth – it is important that we understand and protect them.” Because if these interactions change, this could also affect the biodiversity of entire ecosystems.

Source: Michael Van Nuland (Stanford University) et al., Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073/pnas.2308811121

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