Press release: Are trees exchanging carbon via a wood wide web?

No. 188 - 28.11.2024

Research team led by Göttingen University studies carbon movement from tree to root fungi

The idea of trees "talking" to one another through underground fungal networks – the so-called "wood wide web" – has captured the imagination of the public. This concept, where trees supposedly share nutrients with each other via these networks, has been popularized by books and documentaries. But a new study, led by the University of Göttingen, suggests the reality might be more nuanced. The researchers found that young beech trees could transfer carbon to nearby “ectomycorrhizal” fungi – a kind of fungi that grows on and together with the tree roots in a beneficial relationship – but not to other trees. These fungi form intricate underground connections with tree roots, and it has been suggested they might also connect trees to each other, allowing for mutual nutrient exchange. However, this latest research raises questions about how much actual sharing is going on. The findings were published in New Phytologist.

To trace the movement of carbon, the scientists used a technique called isotopic labelling. They provided CO₂ enriched with a heavier carbon isotope (known as Carbon-13) to a young "donor" beech tree and waited five days, giving the tree time to absorb and move the Carbon-13 to its roots. Then, they measured the carbon in the roots, stems, and leaves of a nearby potential “recipient” tree. Ectomycorrhizal roots – the roots symbiotically associated with these fungi – were of particular interest to the researchers; with a delicate surgical intervention, they separated the plant-tissue from the fungus-colonized-tissue of the root tips and found that Carbon-13 – the marker for donor-derived carbon – was only in the fungus-colonized tissue and not in the rest of the roots of the recipient tree. They repeated the experiment on Douglas firs and again found that the Carbon-13 was only in fungus-colonized tissue, albeit in smaller amounts in this species.

“These findings add fuel to a long-standing debate in ecology: are trees truly interconnected in a cooperative way?” explained postdoctoral researcher, Dr Michela Audisio, at Göttingen University’s Department of Forest Botany and Tree Physiology. She added, "It is hard to imagine that ectomycorrhizal fungi would altruistically transfer carbon from one tree to another. However, there are likely to be advantages for the fungi if can access multiple carbon sources, especially when facing environmental stress." The study also explored what these findings mean for German forests more broadly. The researchers found that ectomycorrhizal roots of Douglas fir, a non-native species, received slightly less of the labelled carbon than European beech, a native species. “This could mean that in forests mixed with Douglas fir, ectomycorrhizal fungi may be less abundant,” said Audisio, “Potentially affecting the forest's carbon cycle.”

This research was part of the RTG 2300 “Enrico” project at the University of Göttingen and was funded by the German Research Foundation (DFG).

Original publication: Audisio M, et al. “Ectomycorrhizal fungi of Douglas‐fir retain newly assimilated carbon derived from neighboring European beech”, New Phytologist 2024. DoI: 10.1111/nph.19943

Contact:

Dr Michela Audisio

University of Göttingen

Department of Forest Botany and Tree Physiology

37077 Göttingen, Germany

Email: michela.audisio@uni-goettingen.de