image: (a) Global map of the predicted MDC stock distribution for the year 2018, along with the changes from 1981 to 2018. The white areas in the left panel and the dark areas in the right panel are the areas with low confidence projections. (b) The relative rates of change in MDC stocks as percentages per annum and per degree Celsius. The dark areas are the areas with low confidence projections. (c) Status of MDC stocks between 1981 and 2018. Bivariate plot comparing the relative rate of change in MDC stock (% per year) against the quantity of MDC stocks. The status categories for the rate of change were determined using confidence intervals, while the MDC stock status groups were established based on quantile distributions (divided into three equal parts). The white areas are the areas with low confidence projections.
Credit: ©Science China Press
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.
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.
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.
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.
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See the article:
Global decline in microbial-derived carbon stocks with climate warming and its future projections
https://doi.org/10.1093/nsr/nwae330
Journal
National Science Review