Microbes in Cold Soil: How They Change When the Ground Thaws

Scientists analyzed 125 samples from five deep cores reaching 15 m below the surface on the Qinghai‑Tibet Plateau. The samples spanned from the active layer—where vegetation thrives—to the frozen permafrost below. By sequencing DNA, researchers examined bacterial communities at each depth and tracked how they shift as the ground warms.

Key Findings

• Bacterial diversity declines with depth.
• Randomness and community cohesion increase deeper in the profile.
• In the active layer, these patterns change noticeably with thaw, whereas they remain relatively stable in the frozen zone.
• A handful of bacterial groups—present throughout the cores—anchor community stability, yet their influence differs between layers.

Carbon Release Implications

• Thawing permafrost reduces the abundance of bacteria linked to carbon storage.
• The relationship between community stability and residual soil carbon strengthens near the surface, suggesting that melting soils could accelerate carbon release.
• This positive feedback may amplify global warming.

Bottom Line

Microbial responses to thaw vary with depth, underscoring the importance of vertical heterogeneity in predicting future carbon emissions from permafrost.