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“Talking” trees and the ecology of underground fungal super-highways

Department of Earth and Environmental Sciences

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Prof D Johnson Applications accepted all year round Self-Funded PhD Students Only

About the Project

Introduction: Recent exciting discoveries have shown that plants respond to herbivore-induced signals from neighbours via underground fungal networks1-3. One implication of this work is that plants ‘communicate’ with signalling molecules produced in response to herbivory by invertebrates from plant to plant via mycorrhizal fungal networks, which affects multitrophic interactions and fitness. There is emerging evidence that plants respond less to signals produced by distantly related individuals compared to closely related individuals4. Much emphasis has been placed on the role of the plants in this process, with the role of the fungus being largely ignored. Yet the fungi are likely to have a vital role in modulating plant-to-plant signalling2. Most plants in nature form symbiotic relationships with mycorrhizal fungi and in fact are entirely dependent on the fungi for acquiring nutrients from soil. The mycorrhizal fungi use energy from plants to produce extensive hyphal networks, which ultimately can inter-connect different species and individuals of plants into large ‘common mycorrhizal networks’, that have numerous functions including facilitating seedling establishment, improving plant nutrition and as conduits of signals5. But there are many uncertainties and fundamental questions that need to be addressed and several assumptions that need to be challenged before recent discoveries on plant-plant signalling can be reliably extrapolated to inform how common mycorrhizal networks function nature. This project tackles these uncertainties and assumptions and will investigate 1) the extent of common mycorrhizal networks formed by trees in nature, 2) the ecological significance of common mycorrhizal networks, and 3) the principal factors that disrupt the function and extent of common mycorrhizal networks. The project has relevance to woodland management strategies, including the protection of natural soil biodiversity to help ecosystem function, and will also tackle fundamental ecological questions leading to high-impact publications and outputs.

Project Summary: The project will use a combination of laboratory and field experiments to tackle the three broad questions, above. This combined approach also enables experiments to be designed that provide rigorous and precise manipulation of specific factors, alongside more ecologically-relevant assessments of functioning of fungal networks in the field. We will undertake several field-based assessments of mycorrhizal network function and distribution. The first will comprise an assessment of the distribution of specific genotypes of ectomycorrhizal fungi in distinct forest plots using molecular markers. Maps of the distribution of fungal genotypes will permit visualization and assessment of the extent of common mycorrhizal networks in different forest types. The second approach will use mesh cores to assess the importance of local common mycorrhizal networks for establishment, colonization by fungi and growth of tree seedlings under different experimental settings. For example, we have access to large-scale climate manipulation experiments and one possible line of inquiry will be to test how drought affects mycorrhizal functioning through impacts on the development of fungal networks. Laboratory experiments will comprise tree seedlings of different relatedness that are inoculated with specific mycorrhizal fungi. They will be grown in systems that permit the formation of common mycorrhizal networks. Once established, individual ‘donor’ trees will be subjected to herbivory and chemical and biological responses of neighbours quantified. Collectively, the results will lead to improved understanding of the factors that govern the function and extent of common mycorrhizal networks. The project provides opportunities for training in molecular biology techniques, sterile techniques, plant and fungal ecology and soil science.

Funding Notes

Tuition Fees: Environmental Band 2 £14,000 (Home), £31,500 Overseas


1Babikova Z, Gilbert L, Bruce TJA, Birkett M, Caulfield JC, Woodcock C, Pickett JA & Johnson D (2013) Underground signals carried through common mycelial networks warn neighbouring plants of aphid attack. Ecology Letters 16, 835-843. DOI: 10.1111/ele.12115.
2Babikova Z, Johnson D, Bruce TJA, Pickett JA & Gilbert L (2013) Underground allies: how and why do mycelial networks help plants defend themselves? BioEssays 36, 21-26. doi/10.1002/bies.201300092/pdf
3Song YY, Simard SW, Carroll A, Mohn WW, Zeng RS. 2015. Defoliation of interior Douglas-fir elicits carbon transfer and stress signalling to ponderosa pine neighbors through ectomycorrhizal networks. Scientific Reports 5: 8495.
4Pickles BJ, Willhelm R, Asay AK, Hahn AS, Simard SW & Mohn WW. Transfer of 13C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas. New Phytologist 214, 400-411.
5Selosse M-A, Richard F, He XH, Simard SW. 2006. Mycorrhizal networks: des liaisons dangereuses? Trends in Ecology and Evolution 21: 621–628.

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