How subsoil microorganisms respond to warming is largely unknown, despite their crucial role in the soil organic carbon cycle. We observed that the subsoil microbial community composition was more responsive to warming compared to the topsoil community composition. Decreased microbial abundance in subsoils, as observed in this study, might reduce the magnitude of the respiration response over time, and a shift in the microbial community will likely affect the cycling of soil organic carbon.

We do not understand the short- and long-term temperature response of soil denitrifiers, which produce and consume N₂O. Boreal forest soils from a long-term climate gradient were incubated in short-term warming experiments. We found stronger N₂O consumption at depth, inconsistent microbial gene abundance and function, and consistent higher N₂O emissions from warmer-climate soils at warmer temperatures. Consideration of our results in models will contribute to improved climate projections.

Global warming leads to increased mineralisation of soil organic matter, inducing a positive climate–carbon cycle feedback loop. Loss of organic matter can be associated with loss of soil structure. Here we use a strong geothermal gradient to investigate soil warming effects on soil organic matter and structural parameters in subarctic forest and grassland soils. Strong depletion of organic matter caused a collapse of aggregates, highlighting the potential impact of warming on soil function.

The sub-humid Argentine Chaco, originally covered by forest, has been subjected to clearing since the end of the 1970s and replacement of the forest by no-till farming. The organic carbon stock content up to 1 m depth varied as follows: forest > pasture > continuous cropping, with no impact of the number of years under cropping. The incorporation of pastures of warm-season grasses was able to mitigate the decrease of C stocks caused by cropping and so could be considered sustainable management.

In this study we evaluated CO₂ emissions during composting of green wastes with clay and/or biochar in the presence and absence of worms, as well as the effect of those amendments on carbon mineralization after application to soil. Our results indicated that the addition of clay or clay–biochar mixture reduced carbon mineralization during co-composting without worms by up to 44 %. In the presence of worms, CO₂ emissions during composting increased for all treatments except for the low clay dose.

Using ranges for variables in a model of organic C stocks of the top 1m of soil on a global 0.5° grid, we assessed the (un)certainty of changes in stocks over the next 75 years. Changes are more certain where land-use change strongly affects carbon inputs and where higher temperatures and adequate moisture favour decomposition, e.g. tropical mountain forests. Global stocks will increase by 1% with a certainty of 75% if inputs to the soil increase due to CO₂ fertilization of the vegetation.