1.Temporal stability of ecosystem productivity is important for providing reliable ecosystem services under global changes. Great efforts have been made to explore the response of aboveground net primary productivity (ANPP) stability to nitrogen (N) enrichment, yet how it affects belowground net primary productivity (BNPP) stability remains elusive, which hinders a comprehensive understanding of ecosystem stability from the view of a whole system.

2. Here, using a field manipulative experiment with six N addition rates (0, 2, 4, 8, 16, 32 g N m-2 year-1), we explored the response patterns and drivers of BNPP stability in the topsoil (0-20 cm) and subsoil (20-40 cm) in the alpine meadow.

3. The results showed that BNPP stability at both soil depths showed a unimodal response to increasing N addition rates. Specifically, for both the topsoil and subsoil, low-level N addition significantly promoted BNPP stability, while high doses of N addition had no significant impact on BNPP stability, suggesting that current low level of N deposition likely benefits the stable provision of belowground functioning. Furthermore, dominant species stability and species richness contributed most to the changes in BNPP stability in the topsoil, whereas only dominant species stability was the dominant driver of BNPP stability in the subsoil.

4. This study is among the first to illuminate the main mechanisms underlying the responses of BNPP stability to N enrichment at various soil depths, which will advance our current understanding of N addition effects on belowground processes and benefit the sustainable provision of ecosystem functioning in the context of atmospheric N deposition.