Fungi regulate response of N 2 O production to warming and grazing in a Tibetan grassland
Lack of understanding of the effects of warming and winter grazing on soil fungal contribution to nitrous oxide (N 2 O) production has limited our ability to predict N 2 O fluxes under changes in climate and land use management, because soil fungi play an important role in driving terrestrial N cycling. Here, we examined the effects of 10 years' warming and winter grazing on soil N 2 O emissions potential in an alpine meadow. Our results showed that soil bacteria and fungi contributed 46 and 54 to nitrification, and 37 and 63 to denitrification, respectively. 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 denitrification to 53 and 55 respectively. Warming significantly decreased enzyme activity of fungal nitrification and denitrification to 47 and 45 respectively, while winter grazing had no such effect. We conclude that soil fungi could be the main source for N 2 O production potential in the Tibetan alpine grasslands. Warming and winter grazing may not affect the potential for soil N 2 O production potential, but climate warming can alter biotic pathways responsible for N 2 O production. These findings indicate that characterizing how fungal nitrification/denitrification contributes to N 2 O production, as well as how it responds to environmental and land use changes, can advance our understanding of N cycling. Therefore, our results provide some new insights about ecological controls on N 2 O production and lead to refine greenhouse gas flux models.