For more than 400 million years, mycorrhizal fungi and plants have formed partnerships that are crucial to the emergence and functioning of global ecosystems.
The importance of these symbiotic fungi for plant nutrition is well established. However, the role of mycorrhizal fungi in transporting carbon into soil systems on a global scale remains under-explored.
This is surprising given that ∼75% of terrestrial carbon is stored belowground and mycorrhizal fungi are stationed at a key entry point of carbon into soil food webs.
A recent study by Merlin Sheldrake, Toby Kiers, Rachael Cargill and Michael Van Nuland analysed nearly 200 datasets to provide the first global quantitative estimates of carbon allocation from plants to the mycelium of mycorrhizal fungi.
They estimate that global plant communities allocate 3.93 Gt CO2e per year to arbuscular mycorrhizal fungi, 9.07 Gt CO2e per year to ectomycorrhizal fungi, and 0.12 Gt CO2e per year to ericoid mycorrhizal fungi. Based on this estimate, 13.12 Gt of CO2e fixed by terrestrial plants is, at least temporarily, allocated to the underground mycelium of mycorrhizal fungi per year, equating to ∼36% of current annual CO2 emissions from fossil fuels.
They explore the mechanisms by which mycorrhizal fungi affect soil carbon pools and identify approaches to increase our understanding of global carbon fluxes via plant–fungal pathways.
Their estimates, although based on the best available evidence, are imperfect and should be interpreted with caution.
Nonetheless, their estimations are conservative, and they argue that this work confirms the significant contribution made by mycorrhizal associations to global carbon dynamics.
Their findings should motivate their inclusion both within global climate and carbon cycling models, and within conservation policy and practice.
⌭ 🖊 & 📸 Current Biology