If you’re a gardener, you may use peat moss - decomposed Sphagnum moss - in soil because it helps retain moisture. 

Peatlands, wetlands characterized by a thick layer of water-saturated, carbon-rich peat beneath living Sphagnum moss, trees, and other plant life, cover just 3 percent of Earth’s land area but may store a third of all soil carbon. That's made possible in large part by microbes. Two microbial processes in particular — nitrogen fixation and methane oxidation — strike a delicate balance, working together to give Sphagnummosses access to critical nutrients in nutrient-depleted peatlands. 

These two processes are a vital part of of nutrient cycling in peatlands and a new paper estimates what may happen if the climate change impacts of simulations becomes reality. Most peatlands are in northern climates. 

Their computer simulations include the effects of increasing temperature and carbon dioxide on the growth of Sphagnum moss, its associated microbiome, and overall ecosystem health To go beyond conjecture, they turned to the ORNL Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment — a field lab in northern Minnesota where the team warms peat bogs and experimentally changes the amount of carbon dioxide in the atmosphere. Starting in 2016, the team exposed different parts of SPRUCE’s experimental peatlands to a gradient of higher temperatures ranging from an increase of 0°C to 9°C, capturing the Intergovernmental Panel on Climate Change models’ predicted 4°C to 6°C increase in northern regions by 2100.

The moss’s reaction was significant. Although nearly 100% of the bog’s surface was covered in moss at the beginning of the experiment, moss coverage dropped with each increase in temperature, plummeting to less than 15% in the warmest conditions.

Critically, the two microbial processes that had previously been consistently linked fell out of sync at higher temperatures. Peatlands are extremely nutrient-poor and microbial nitrogen fixation, the process of turning atmospheric nitrogen into an organic compound that the moss can use for photosynthesis, represents a major nitrogen input to the ecosystem, In addition, methane oxidation allows the moss to use methane released from decomposing peat as energy. They found that those two processes, which are catalyzed by the Sphagnum microbiome, become disconnected as the moss dies.