Trees are moving to soils that lack the fungi to support them

As our planet warms, many species are relocating to new areas, but trees are lagging behind other plants and animals. A recent study published in the journal Proceedings of the National Academy of Sciences (PNAS) suggests that the reason for this delay in tree migration might be found underground – in soil fungi. 

The researchers found that trees, especially those in northern regions, may be moving to soils that lack the mycorrhizal fungi necessary to support them.

Trees and soil fungi in a warming world 

Most plants, including large coniferous trees in northern latitudes, rely on symbiotic relationships with mycorrhizal fungi. These microscopic fungi form networks in the soil, connecting with plant roots to supply essential nutrients in exchange for carbon. 

The study showed that 35% of tree-fungi partnerships could be negatively impacted by climate change, according to lead author Michael Van Nuland, a fungal ecologist at the Society for the Protection of Underground Networks (SPUN).

Diverse soil fungi help trees survive

The trees most at risk in North America belong to the pine family. The study highlighted that trees on the edges of their ranges, where conditions are harshest, have higher survival rates when they have more diverse mycorrhizal fungi. This diversity is critical for helping trees withstand climate change.

“Ectomycorrhizal fungi have a different relationship to climate than ectomycorrhizal trees do,” explained co-author Clara Qin, a data scientist at SPUN. 

“While we expect climate-driven migrations to be limited by abiotic factors like the availability of space at higher latitudes and elevations, we don’t usually account for biotic limitations like the availability of symbiotic partners.”

Assisted migration strategies 

“It’s absolutely vital that we continue to work to understand how climate change is affecting mycorrhizal symbioses,” Van Nuland added. “These relationships underpin all life on Earth – it’s critical that we understand and protect them.”

“While more empirical work on this topic is certainly warranted, it may help explain previous observations of migration failure amongst a wide range of North American tree species. Consequently, our findings suggest that mycorrhizal fungi will need to be carefully considered as part of any assisted migration strategies for North American tree species,” the authors concluded.

Pine trees of North America

The pine family, scientifically known as Pinaceae, is a prominent group of coniferous trees that are widespread across North America. This family includes not only pines but also firs, spruces, cedars, and larches, among others. 

Pine tree characteristics

These trees are characterized by their needle-like leaves, which are typically evergreen, and their cone-bearing reproductive structures. 

Pines, in particular, are known for their long, slender needles grouped in clusters called fascicles, which can contain anywhere from one to five needles depending on the species.

Pine species diversity 

In North America, the diversity of pine species is significant, adapting to a wide range of climates and soils. They are found from the cold boreal forests of Canada, where species like the white pine and red pine thrive, to the warm southern regions where species like the ponderosa and lodgepole pine are common. 

Ecological and economic significance 

The adaptability of these trees makes them ecologically important as they provide habitat and food for wildlife, help in soil stabilization, and contribute to the forest’s fire dynamics due to their flammable resin.

Economically, the pine family is equally significant. Many species are harvested for timber and paper production, and pine trees are also popular as Christmas trees due to their appealing fragrance and shape. 

The resilience and utility of the pine family make it a vital component of North American forests, both in natural settings and in managed landscapes.

Role of soil fungi in tree health

Soil fungi play a crucial role in the health and growth of trees primarily through their symbiotic relationships with tree roots. These fungi, particularly mycorrhizal fungi, extend their networks into the soil, greatly expanding the surface area of tree roots. 

Water and essential nutrients

This increased surface area allows trees to absorb water and essential nutrients, like phosphorus and nitrogen, more efficiently than roots could on their own. 

In return, the fungi receive carbohydrates produced by the trees through photosynthesis, which are vital for their growth and reproduction.

Fungi and soil structure 

Moreover, soil fungi improve the soil structure, which enhances water retention and aeration, providing a better growing environment for trees. 

Soil composition 

Fungi also play a key role in decomposing organic matter in the soil, which recycles nutrients that are essential for the ecosystem’s sustainability. 

This interaction not only boosts tree health but also enhances their resistance to various stresses, including drought and diseases, helping maintain the overall resilience and stability of forest ecosystems. 

By fostering a complex web of interactions within the soil, fungi contribute significantly to the ecological success and longevity of trees.

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