| Summary: | Natural montane peatlands are generally not a significant source of nitrous oxide (N<sub>2</sub>O) due to environment limitations, including phosphorus (P) scarcity and temperature lowness. Phosphorus enrichment and warming caused by global change are altering these limitations, and are likely to increase the source function of N<sub>2</sub>O. However, the combined effects of P addition and warming on N<sub>2</sub>O fluxes and biotic/abiotic factors in peatlands are still uncertain. To address this, we investigated the long-term (12 yrs) effects of P addition (5 and 10 kg ha<sup>−1</sup> yr<sup>−1</sup>) and its interaction with warming on N<sub>2</sub>O fluxes in a peatland. The results showed that although long-term P addition did not significantly affect the source/sink function of N<sub>2</sub>O in the peatland, it stimulated enzyme activities and promoted peat decomposition. However, warming amplified the effect of P addition to increase N<sub>2</sub>O emissions by stimulating enzyme activities and changing soil stoichiometry, so even turned the peatland into a significant source of N<sub>2</sub>O with an emission of approximate 100 g m<sup>−2</sup> during the growing season. Our study suggests that P enrichment against the current background of global warming will enhance the possibility of strong N<sub>2</sub>O emissions in montane peatlands, which may increase the risk that global warming will be further aggravated.
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