Many plant species benefit from the fungi that grow on and around them. A collaborative study from the University of Texas, Boston University and the Smithsonian Tropical Research Institute have recently discovered that the atmosphere also receives positive gains from this relationship and could be a key in the fight against climate change.
The symbiotic relationship between a fungus and a plant that takes place in their intertwined root systems is called mycorrhiza. A specific type of mycorrhiza, in which the fungi do not penetrate their host cell walls, is called ectomycorrhizal fungi. In this exchange, the fungi’s roots form a criss-crossed pattern-like structure, known as the Hartig net, around the plant’s roots at the cellular level. As the plants gather energy from the sun through photosynthesis, carbohydrates are passed to the fungus. In return, the fungus gives the plant water and minerals from the soil.
Plants are the most adept organisms at pulling in carbon dioxide from the atmosphere, making them a staple in the battle against climate change. However, this is temporary as when every plant dies, all the carbon dioxide absorbed from the atmosphere becomes part of the soil as they decompose. The rate at which carbon dioxide leaves the soil therefore can have a huge impact on the amount of the greenhouse gases in the atmosphere and ultimately the pace of global warming.
The researchers in the study profiled more than 200 soil composites from around the world. They found that soils dominated ectomycorrhizal fungi contained as much as 70% more carbon than soils dominated by arbuscular mycorrhizal fungi — fungi that do penetrate their hosts on a cellular level. This is because the ectomycorrhizal fungi extract nitrogen much more efficiently and quickly than their fungi counterparts. As they pull in nitrogen, it slows down their ability to break down dead plant matter. In turn, this slows down the amount of carbon released back into the atmosphere and keeps it locked away in the soil.
Ectomycorrhizas only form on the roots of around 2% of plant species, typically woody plants like birch, beech, willow, pine and rose. They are also vulnerable to nitrogen pollution caused by agricultural run-off. Losing these fungi could pump even more carbon and gases into the atmosphere and would further accelerate climate change. Scientists are hopeful, however, that further study of these fungi could lead conservation efforts to focus more on these specific plants that harbor the magical carbon storing mushrooms.