In a meta-analysis, scientists estimated that 13.12 billion tons of fixed carbon dioxide equivalent (CO2e) per year from terrestrial plants were allocated to mycorrhizal fungi, roughly equivalent to 36% of annual global fossil fuel emissions. The study was published June 5 in the journal Current Biology.
Mycorrhizae (a fungus) have “nourished” terrestrial life for at least 450 million years by providing plants with the soil nutrients they need to grow. In recent years, scientists have discovered that, in addition to forming symbiotic relationships with almost all land plants, these fungi are important conduits for transporting carbon to soil ecosystems.
Since 70%~90% of land plants form symbiotic relationships with mycorrhizal fungi, researchers have long speculated that a large amount of carbon must enter the soil through these networks.
“We may have overlooked a major carbon pool.” Author Heidi Hawkins, head of research at the South African Conservation Society and the University of Cape Town, said: “We know that protecting and restoring forests is a natural way to mitigate climate change. But little attention has been paid to the fate of the vast amounts of carbon dioxide absorbed by plants using photosynthesis. In effect, this carbon dioxide is sent to the mycorrhizal fungus underground. ”
Mycorrhizal fungi pass on nutritious minerals to plant partners and obtain carbon from plant partners. These two-way exchanges are achieved with the help of connections between fungal mycelium and plant roots. Fungal mycelium is a filamentous network that makes up the bulk of the fungal biomass. Once the carbon is transported underground, it is used by mycorrhizal fungi to grow a wider range of mycelium in order to help them explore the soil. Carbon is also bound in the soil by sticky compounds released by fungi and remains underground in the form of fungal necrotic masses, becoming structural scaffolds for the soil.
Scientists know that carbon flows in fungi, but how long it stays in the fungus is unclear. “A major gap in our knowledge is the persistence of carbon in mycorrhizal structure. We know that it is a flux that retains some carbon in the mycorrhizal structure during the fungus lifetime, even after its death. “Some break down into small molecules that then combine with particles in the soil and even be reused by plants.” Of course, during the respiration of other microorganisms or the fungus itself, some carbon is released in the form of carbon dioxide. ”
The paper advances the exploration of the role fungi play in Earth’s ecosystem. “We know that mycorrhizal fungi are vital ecosystem ‘engineers’, but they are invisible.” Toby Kiers, corresponding author of the paper, professor of evolutionary biology at Vrije Universiteit Amsterdam in the Netherlands and co-founder of the Society for the Protection of Subsurface Networks (SPUN), said: “Mycorrhizae lie on the basis of the food web that supports most of life on Earth, but we are only just beginning to understand how they actually work. There’s still a lot to learn. ”
But understanding and protecting these fungi is a race against time. The Food and Agriculture Organization of the United Nations warns that 90% of soils could be degraded by 2050, but fungi are excluded from most conservation and environmental policies. Without the fertility and structure provided by the soil, the productivity of both natural plants and crops can decline rapidly.
“Mycorrhizal fungi represent blind spots for carbon modeling, conservation and restoration.” Co-author Katie Field, professor of plant-soil processes at the University of Sheffield in the UK, said: “Soil ecosystems are being disrupted at an alarming rate by human activities such as agriculture and development, but little is known about the wider effects of soil community destruction. When we destroy ancient life support systems in soil, we undermine efforts to limit global warming and undermine the health and resilience of ecosystems. ”
“Many human activities have destroyed underground ecosystems. In addition to limiting destruction, we also need to radically increase the speed of research. “Organizations like SPUN, the Fungus Foundation, and GlobalFungi are leading a large-scale global sampling effort to create an open-source map of the Earth’s fungal network.” These maps will help reveal the properties of subsurface ecosystems, such as carbon sequestration hotspots, and document new fungal species that can withstand drought and heat. ”
The researchers stress that although their data is based on the best available evidence, it is not perfect and should be interpreted with caution. “Although we are only an estimate, this is the best we can get with the data we have. Research limitations clearly indicate that further empirical studies of carbon and nutrient flows between plants and mycorrhizae are urgently needed. Sheldrake said. (Source: Feng Weiwei, China Science News)
Image courtesy of Pixabay
Related paper information:http://doi.org/10.1016/j.cub.2023.02.027