Effects of nitrogen addition on anaerobic oxidation of methane in Zoige Plateau peatlands

Abstract

Anaerobic oxidation of methane (AOM), an important biological process to reduce global methane emissions to the atmosphere, can utilize methane as an electron donor to reduce sulfate, nitrate, nitrite, iron, manganese, AQDS (9,10-anthraquinone-2,6-disulfonate), etc.; thus, AOM has been a hot topic in global climate change research in recent years. In addition, nitrogen deposition of terrestrial ecosystems can input more nitrogen to nitrogen-limited peatlands, which could impact the AOM process. However, the effect of nitrogen addition on AOM is not well studied. Here, we investigated the effects of two forms of nitrogen on the vertical distribution (0–100 cm) of AOM in the Zoige peatlands (China) using an anaerobic incubation experiment. The results show that the concentrations of inorganic nitrogen species changed with nitrogen addition, but it did not significantly promote the potential of AOM. The cumulative AOM of treatments without nitrogen (CK) and ammonium chloride (Nred) was 2343.43 ± 18.96 µg·g−1 and 2340.76 ± 16.11 µg·g−1, respectively, which were significantly higher than that of sodium nitrate (Nox) addition treatment (2098.13 ± 13.59 µg·g−1). In addition, the potential of AOM increased with depth, but different soil layers had different responses to the two forms of nitrogen, which could reflect the variable need for different forms of nitrogen in the different soil layers. The soilwatercontent(SWC), dissolved organic carbon (DOC), iron content (Fe3+), and pH played important roles in the potential of AOM in the Zoige peatlands. Overall, our results found that nitrogen addition did not increase the potential of AOM, but instead had an inhibitory effect on it. This study provides a basis for understanding the response of AOM to nitrogen addition in peatlands, which has important implications for global climate change.