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News Article

The knock-on effects of pollution on European forests through mycorrhizal fungi

Researchers at Imperial College London and Royal Botanic Gardens, Kew, have conducted a Europe-wide study on the influence of environment and host variables on the presence of ectomycorrhizal symbionts.

Mycorrhizae are a group of fungi which directly interact with the roots of higher plants in order to facilitate exchange of nutrients between the soil and the plant. Ectomycorrhizae are those which specifically live on the external surface of plant roots, creating a sheath-like structure around the plants tissue, called a mantle, and between the plants cells, called a Hartig net. Around 2% of plant species have some form of ectomycorrhizal association but they are very common across temperate forests including pine, oak, beech and birch.

The basis of this mutualistic relationship is that the fungus receives carbon from the plant and in return the fungi provides more efficient uptake of water and nutrients, including nitrogen, phosphorous and potassium, from the soil surrounding the plant, allowing it to endure adverse conditions. Though they may be hidden from our view the majority of the time it is likely you would recognise and maybe have eaten some mycorrhizal fungi, for instance truffles.

In a paper published this week, researchers at Imperial College London and the Royal Botanic gardens, Kew, collected 13,000 soil samples, containing 40,000 root samples, from 137 sites across 20 European countries in an enormous 10 year study seeking to uncover the reasons behind the increase in tree malnutrition noted across Europe. Symptoms of this malnutrition can include discoloured leaves or shedding leaves from the crown.

Lead researcher Dr Martin Bidartondo, from the Department of Life Sciences at Imperial and Kew Gardens: “Processes happening in soil and roots are often ignored, assumed or modelled, because studying them directly is difficult, but it is crucial for assessing tree functioning”

Tree characteristics, such as species and nutrient status, air and soil quality were all found to impact mycorrhizae more strongly than previously thought. Higher levels of nitrogen and phosphorous specifically were suggested to lead to an increase in more ‘tolerant’ species, possibly resulting in a greater occurrence of ‘parasitic’ mycorrhizae which are less beneficial or actively detrimental to their host tree.

Dr Laura M Suz, mycology research leader at Kew Gardens said: “The thresholds uncovered in this study should impact how we manage our forests”

Differences between European and North American legislation on how pollutant chemicals such as these are regulated are thought to be a reason for the superior health of North American forests and should be used as an example for Europe to follow in order to maintain healthy mycological communities.

Dr Martin Bidartondo - “In North America the limits are set much lower, and we now have good evidence they should be similar in Europe”

The importance of mycorrhizal relationships for maintaining healthy temperate and boreal forests is still being discovered. This study has helped to better understand the limits of certain elements such as nitrogen and phosphorous, where they switch from being nutrients to pollutants. However, the key takeaway from this research is the understanding that pollution continues to have profound and seemingly never-ending impacts as we continue to study our changing environment in greater detail.

Read the full paper here: van der Linde, S., Suz, L., Orme, C., Cox, F., Andreae, H., Asi, E., Atkinson, B., Benham, S., Carroll, C., Cools, N., De Vos, B., Dietrich, H., Eichhorn, J., Gehrmann, J., Grebenc, T., Gweon, H., Hansen, K., Jacob, F., Kristöfel, F., Lech, P., Manninger, M., Martin, J., Meesenburg, H., Merilä, P., Nicolas, M., Pavlenda, P., Rautio, P., Schaub, M., Schröck, H., Seidling, W., Šrámek, V., Thimonier, A., Thomsen, I., Titeux, H., Vanguelova, E., Verstraeten, A., Vesterdal, L., Waldner, P., Wijk, S., Zhang, Y., Žlindra, D. and Bidartondo, M. (2018). Environment and host as large-scale controls of ectomycorrhizal fungi. [online] Available at:


To find more than 62,000 related papers use this search string in the Forestry Database:

("forest*" OR "woodland*") AND ("mycorrhizal fung*" OR "mycorrhizas" OR "roots" OR "soil flora" OR "soil fungi")