Winter is a time when we think of dormancy. Chipmunks have begun hibernating. The deciduous trees have lost their leaves. Herbaceous plants are resting belowground as bulbs, rhizomes, etc. But, not every living thing in the forest is resting during the winter. Soil microbes are still active. Though they slow down a bit, they are still hard at work in the frosty conditions of winter!

Soils are teeming with a diverse group of organisms; it might be the most diverse habitat on earth! Microscopic animals, insects, protists, algae, bacteria, and fungi all call soil home. Fungi especially play a crucial role in soil, as the main decomposers of organic matter and a primary plant partner involved in nutrient acquisition and disease suppression. Fungi are one of the reasons why the soil ecology lab here at HF&G is interested in studying soil at all.

Seventeen years ago, David Burke (Vice President of Science and Conservation) began wondering just what happens to soil fungi in the winter. Beginning in 2006 and each year since, Burke and his team have been trekking up to our long-term research plots in Stebbins Gulch to collect soil during each season, including the winter. Over the years, the winter trek was sometimes during a polar vortex and sub-zero temperatures. Other years, winter sampling meant hiking through snow up to our knees. But, each year of data has meant learning more about a group of organisms that we still have so much to learn about.

So, what does happen to soil fungi in winter? Our findings suggest that winter is not much different for fungi than other times of the year. Decomposition does slow down with the colder temperatures, but the taxa remain. Over multiple years, the fungi that we see in soils collected in spring, summer, and fall are pretty much the same as the ones we see in soils collected in winter. Fungi belowground do turnover, meaning that the suite of taxa found at different time points will change. But, our results show that the chilly temperature of winter is not the reason for this turnover. The environmental conditions that are important for fungi and that drive the turnover are water and nutrients, such as carbon, phosphorus, and nitrogen. This means that winter is not a time of dormancy for many taxa of fungi. As long as the necessary water and nutrients are available, the fungi will continue on.

Winter is a great time to celebrate fungi in the soil! This is because each year on December 5^th, we observe World Soil Day. This is a day begun by the Food and Agriculture Organization of the United Nations to recognize the invaluable role of soil and to take measures to conserve this resource for future generations. Here at HF&G we will be celebrating World Soil Day with another winter hike to collect soil and our continued research on fungi even as the snow falls and the frost moves in. Winter for us is the same as for the fungi; status quo.

Further reading:
Burke, D.J. (2015) FEMS Microbiology Ecology 91; fiv053; doi: 10.1093/femsec/fiv053
Burke, D.J. et al. (2019) Ecosphere 10; e02896; doi: 10.1002/ecs2.2896