Input of organic substances into soil often accelerates the mineralization of soil organic C (SOC), a phenomenon termed the priming effect (PE), which could mediate the turnover rate of C and nitrogen (N) in soil, influencing the competition for nutrients between plants and soil microorganisms. Atmospheric N deposition has increased by almost one order of magnitude during the last century, and changed terrestrial C cycling considerably. As a critical part of C cycling in terrestrial ecosystem, PE was also affected by atmospheric N deposition. However, few results was obtained on the impacts of atmospheric N depositionon PE.

To fill this research gap, research group in Institute of Applied Ecology, CAS took advantage of a long-term N deposition simulation site at the Maoershan Forest Research Station of Northeast Forestry University in northeastern China (127°30′~127°34′E, 45°20′~45°25′N) to explore the response of PE to N deposition with various chemical forms. They found that the magnitude of PE was regulated by the form of N deposition and the amount of labile C input interactively (Fig. 1). Organic N deposition decreased the PE induced by glucose by 12.3-23.2% relative to the control.

In addition, the inhibitory effect of organic N deposition on PE became stronger with the increase in the glucose addition level. In contrast, no response of PE was found to inorganic N deposition or the mixed deposition of inorganic and organic N deposition at a ratio of 7:3. Organic N deposition significantly decreased SOC loss through mediating the PE, resulting in the net annual increase in SOC by 27.2% compared to the control.

This research emphasized the important role of the form of N deposition and the amount of labile C input in regulating the PE of SOC decomposition. The results would help to explore the coupling pattern of C and N in terrestrial ecosystems, taking a step forward for constraining the climate change model.

This research was published in Plant and Soil with the title of “Organic N deposition favours soil C sequestration by decreasing priming effect”. Dr. Peng Tian from Huitong Experimental Station of Forest Ecology, CAS Key Laboratory of Forest Ecology and Management was the first author, and Researcher Qingkui Wang from Huitong National Research Station of Forest Ecosystem was the corresponding author of this article.

This research was supported by the National Key Research and Development Program of China  and the National Natural Science Foundation of China.