An unexpected outcome of atmospheric CO2 enrichment

Unseen belowground interactions impact the composition of natural plant communities. Mycorrhizae, symbiotic associations between soil fungi and plant roots, help plants acquire soil nutrients but also drain substantial carbon from plants. Whether mycorrhizae help or hinder plant growth depends upon the balance between nutrient benefits and carbon costs.

Mycorrhizae can structure plant communities because they improve the growth of some plant species more than others. In the forthcoming issue of Ecology Letters, Johnson, Wolf and Koch demonstrate that enrichment of atmospheric CO2 and soil N interacts with mycorrhizae to structure the species composition of experimental plant communities.

Distinctly different communities arose from identical starting conditions depending on the presence or absence of mycorrhizal fungi and the levels of atmospheric CO2 and soil N. This study emphasizes the need to consider mycorrhizal interactions when predicting plant community responses to global change factors.

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