Scientists predict the spatial-temporal dynamics of soil microbial-derived carbon stocks

Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems and plays a crucial role in mitigating climate change and enhancing soil productivity. Microbial-derived carbon (MDC), accounting for about half of the total SOC pool, is the main component of the persistent SOC pool.

However, our limited understanding of the spatial and temporal dynamics of MDC stocks at the global scale hampers our ability to assess the long-term effects of global warming on persistent SOC sequestration.

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To fill this gap, the research team led by Jiabao Zhang and Yuting Liang, researchers at the Nanjing Institute of Soil Science, Chinese Academy of Sciences, in collaboration with Shenyang Institute of Applied Ecology, Aarhus University (Denmark), University of Kassel (Germany), ETH Zurich (Switzerland), University of Oklahoma (USA), and other domestic and foreign research units, predicted the spatial-temporal dynamics of soil microbial-derived carbon stocks. The relevant research results are described as ’Global decline in microbial-derived carbon stocks with climate warming and its future projections’, published online in National Science Review.

Forecasting dynamics

In this study, this team compiled an extensive global dataset and employed ensemble machine learning techniques to forecast the spatial-temporal dynamics of MDC stocks across 93.4% of the total global land area from 1981 to 2018. This work revealed that for every 1°C increase in temperature, there was a global decrease of 6.7 Pg in the soil MDC stock within the predictable areas, equivalent to 1.4% of the total MDC stock or 0.9% of the atmospheric C pool.

The tropical regions experienced the most substantial declines in MDC stocks. They further projected future MDC stocks for the next century based on shared socioeconomic pathways, showing a global decline in MDC stocks with a potential 6-37 Pg reduction by 2100 depending on future pathways.

Positive feedback loop

MDC is crucial for maintaining the long-term stability of SOC. A decrease in MDC suggests that a substantial portion of the stable SOC could be released into the atmosphere as carbon dioxide (CO2), creating a positive feedback loop between atmospheric and soil carbon reservoirs.“These results offer an empirical foundation for refining the temperature dependency of MDC stocks within atmosphere‒soil carbon cycle models.” Liang says.

This study underscores that global warming will lead to a decrease in global MDC stocks, which could have severe ecological repercussions for climate change, food security, and ecosystem integrity. The researchers recommend integrating the response of MDC stocks to warming into socioeconomic models to enhance confidence in selecting sustainable pathways.