A research team led by Prof. YANG Yuanhe from the Institute of Botany of the Chinese Academy of Sciences (IBCAS), in collaboration with partners, has found that prolonged warming significantly reduces soil nitrogen (N) stocks in Tibetan permafrost ecosystems.

The findings, published in Nature Geoscience, provide field-based evidence that soil N vulnerability under climate warming may unfold faster than previously assumed.

In this study, the researchers showed the long-term trajectory from a ten-year (2014-2023) field warming experiment in a permafrost ecosystem on the Tibetan Plateau. Over a decade of field study, they tracked the long-term trajectory of soil N stocks by repeatedly sampling both N content and the corresponding bulk density in the top 50 cm. Although no change was detected during the early years, eight years of warming ultimately reduced topsoil N stocks by 7.7%.

To the potential mechanisms of warming-induced changes in soil N stocks, the researchers also compiled a full ecosystem N inventory by measuring 28 N-cycling variables, including N inputs, microbial N transformations and N losses, and performed a DeNitrification-DeComposition model. 

They found that the decline in topsoil N stocks could be largely attributed to greater N retention by plants, along with increased N losses through leaching and gaseous emissions. A meta-analysis across permafrost regions of the Northern Hemisphere further confirmed these observations and modelling results.

Together, these findings underscore the vulnerability of soil nitrogen pools to sustained warming in permafrost ecosystems. They also suggest the possibility that nitrogen-climate feedbacks could intensify more rapidly than currently project.

The effects of decadal warming on soil nitrogen stocks in a permafrost ecosystem on the Tibetan Plateau (Image by WEI Bin)