Arbuscular Mycorrhizal Fungi Increase Organic Carbon Decomposition Under Elevated CO 2

A Fungal Culprit to Carbon Loss In some ecosystems, such as in the layer of soil containing plant roots, fungi, and bacteria, increased levels of CO 2 should stimulate more efficient aboveground photosynthesis, which in turn should promote increased sequestration of organic carbon in soil through the protective action of arbuscular mycorrhizal fungi. However, in a series of field and microcosm experiments performed under elevated levels of CO 2 thought to be consistent with future emissions scenarios, Cheng et al. (p. 1084 ; see the Perspective by Kowalchuk ) observed that these fungi actually promote degradation of soil organic carbon, releasing more CO 2 in the process.