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How do bacteria and fungi support nutrient cycling in tundra soils?

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tundra biome — Polar ecosystem Southern limit of Arctic tundra and approximate line of demarcation between Low and High Arctic.

In tundra ecosystems, bacteria and fungi are essential to the functioning of the biome, as they drive critical biogeochemical processes that sustain life. These microbial communities support nutrient cycling through several key functions:1

Nutrient Regeneration: Microbes and fungi are responsible for the decomposition of organic matter, a process that releases essential nutrients back into the soil, making them available for plant growth.12
Carbon Cycling: These organisms play a central role in the carbon cycle by breaking down organic material. Their activity levels fluctuate seasonally in response to changes in soil temperature, moisture, and carbon availability.1
Nitrogen Fixation: Soil microbes contribute to the ecosystem by fixing nitrogen, which is a vital nutrient for plant development.2

While these processes are fundamental, they are often limited by the cold temperatures characteristic of the tundra, which slow the rate of decomposition. Furthermore, the activity of these microbes is largely confined to the "active layer" of the soil—the surface portion that thaws during the summer. If permafrost thaws due to climate change, it exposes long-frozen organic matter to increased microbial decomposition, which can release significant amounts of carbon dioxide and methane into the atmosphere.234