Fungi regulate the response of the N2O production process to warming and grazing in a Tibetan grassland

Lack of understanding of the effects of warming and winter grazing on soil fungal contribution to the nitrous oxide (N₂O) production process has limited our ability to predict N₂O fluxes under changes in climate and land use management, because soil fungi play an important role in driving terrestrial N cycling. A controlled warming and winter grazing experiment that included control (C), winter grazing (G), warming (W) and warming with winter grazing (WG) was conducted to investigate the effects of warming and winter grazing on soil N₂O production potential in an alpine meadow on the Tibetan Plateau. Our results showed that soil bacteria and fungi contributed 46 ± 2% and 54 ± 2% to nitrification, and 37 ± 3% and 63 ± 3% to denitrification in the control treatment, respectively. We conclude that soil fungi could be the main source of N₂O production potential for the Tibetan alpine grasslands. In our results, neither warming nor winter grazing affected the activity of enzymes responsible for overall nitrification and denitrification. However, warming significantly increased the enzyme activity of bacterial nitrification and potential of N₂O production from denitrification to 53 ± 2% and 55 ± 3%, respectively, but decreased them to 47 ± 2% and 45 ± 3%, respectively. Winter grazing had no such effects. Warming and winter grazing may not affect the soil N₂O production potential, but climate warming can alter biotic pathways responsible for N₂O production process. These findings confirm the importance of soil fungi in the soil N₂O production process and how they respond to environmental and land use changes in alpine meadow ecosystems. Therefore, our results provide some new insights into ecological controls on the N₂O production process and contribute to the development of an ecosystem nitrogen cycle model.