Mineral and climatic controls over soil organic matter stability across the Tibetan alpine permafrost region

Abstract:

Adequate understanding on patterns and drivers of soil organic matter (SOM) stability can contribute to predicting permafrost carbon (C) cycle and its feedback to climate change. However, due to the limited observations, it remains unknown whether biochemical selectivity or physical-chemical protection dominates SOM stability in permafrost regions. By combining large-scale field sampling (103 sites) with thermal analysis technique, this study explored the spatial patterns and fundamental drivers of SOM stability across the Tibetan alpine permafrost region. Our results showed that SOM stability exhibited an increasing trend from the southeastern to northwestern plateau. Such a pattern was directly regulated by mineral and indirectly by climatic variables. The stronger SOM stability was related to higher mineral-organic associations and more arid conditions. By contrast, substrate quality had limited effects on SOM stability. Overall, these results provide the empirical evidence for the physical-chemical protection hypothesis, highlighting the importance of considering mineral in the Earth System Models to precisely predict soil C dynamics across the permafrost regions.