When snow blankets the landscape, it may seem like life slows down. But beneath the surface, an entire world of activity is unfolding. “Unlike many plants or some animals, which tend to go dormant or are much less active during winter, soil microbes are actually very active under winter snowpacks,” says Patrick Sorensen , a soil microbiologist and assistant professor of soil ecology and biogeochemistry in the University of Rhode Island’s Department of Natural Resources Science.
All winter, soil microbes decompose organic matter, releasing nutrients that are critical for plants. By spring, these nutrients are perfectly timed to fuel new growth. Warming winters and reduced snow cover can disrupt this timing, allowing nutrients to wash into streams, escape into the air, or leave plants short of what they need.
Microbial bloom
When snow melts, microbial activity surges. The soil microbial population size “blooms” as it seizes nutrients released by melting snow and rising groundwater, then eventually “crashes” when the soil is depleted of these resources. This cycle produces a pulse of nitrogen that shapes soil fertility. While scientists have observed this pattern globally, the mechanisms behind it have been unclear.
New research by Sorensen and colleagues, published in Nature Microbiology , shows that distinct groups of microbes orchestrate this seasonal nitrogen cycling. Winter-adapted microbes thrive at low soil temperatures, snowmelt specialists peak for a short window of time when soils are saturated with snow melt, and spring-adapted microbes dominate once soils warm up. Each group plays a different role in recycling nitrogen: winter and snowmelt microbes break down organic compounds like amino acids for both energy and biomass, while spring microbes help convert nitrogen into forms plants can use, sometimes retaining it in the soil and sometimes allowing it to escape.
Rethinking nitrogen in soil
The study challenges long-held assumptions about how microbes build biomass. Traditionally, scientists focused on a few inorganic nitrogen transformations, but Sorensen’s team found that soil microbes actively transform thousands of organic nitrogen compounds. They also discovered that some microbes coordinate both organic and inorganic nitrogen transformations and even interact with other species to recycle nitrogen more efficiently.
By using organic nitrogen to grow and generate energy, different microbial groups coordinate complex nitrogen transformations under snowpacks, and understanding these trait-based interactions may help predict how nutrient cycling responds to climate change.
These findings suggest that soil nitrogen cycling is far more dynamic and complex than previously understood. Depending on which microbial groups are active and when, microbes can either promote nitrogen loss by converting nitrate into gases that escape to the atmosphere or enhance nitrogen retention by recycling it into forms available to plants or re-used by other microbes.
“We were surprised to see how central organic nitrogen recycling was to fueling such large microbial population changes,” Sorensen says. “It shows that nitrogen cycling during snowmelt is driven not just by simple inorganic transformations, but by complex interactions among microbes, organic matter, and changing environmental conditions.”
Timing matters in a warming world
These seasonal microbial dynamics are tightly linked to plant nutrient needs. Nutrients released during microbial population collapse often become available just as plants begin growing in spring. But climate change is threatening this synchronization.
“We think microbial nutrient release during winter and plant nutrient uptake in spring are currently well aligned,” Sorensen says. “With warmer winters and reduced snowpack, that timing could become decoupled.”
Earlier snowmelt and thinner snowpacks may reduce winter microbial activity or shift it earlier in the year, increasing the risk that nitrogen is lost to streams, lakes, and the atmosphere before plants can use it. At Sorensen’s Colorado field site, snowmelt now occurs roughly three weeks earlier than it did 50 years ago, and low-to-no snow winters are expected to become increasingly common across the Western United States.
“It is important to emphasize that these stark changes in our environment are likely to happen within many of our lifetimes, not in some distant time in the future,” he says. “This could adversely affect forest health in both the Western and Eastern United States; for example, increasing the frequency of forest fires out West or increasing outbreaks of tree pathogens in Eastern forests. We may have better options to manage adverse outcomes if we have a better understanding of overwinter microbial processes.”
The research was made possible by Sorensen’s collaboration among scientists with expertise in microbial ecology, biogeochemistry, genomics, and metabolomics; he says his co-authors’ unique expertise made the project truly a “team-science effort.”
Looking ahead, he is eager to explore new questions raised by the work, including whether antifreeze compounds produced by microbes beneath snowpacks influence methane cycling during snowmelt, a connection previously observed in marine systems but not yet documented in soils.
Ultimately, Sorensen hopes the research encourages people to see snowy ecosystems in a new light. “The next time you’re cross-country skiing or snowshoeing through a forest,” he says, “pause to appreciate that there’s a robust, active microbial community living—and likely thriving—beneath the snow.”
Nature Microbiology
Observational study
Not applicable
Multi-omics reveals nitrogen dynamics associated with soil microbial blooms during snowmelt
27-Jan-2026