Nitrate availability modulates the temperature effect on N 2 O and N 2 production from denitrification
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Nitrous oxide (N 2 O) can be both produced and subsequently reduced to dinitrogen gas (N 2 ) via canonical denitrification, making the balance between these steps a key control on the net flux of this potent climate gas. Through a meta-analysis, we showed that net N 2 O and N 2 production from denitrification respond differently to temperature, exhibiting distinct temperature sensitivities. In addition, nitrate availability plays a critical role in regulating this balance, yet only few studies have examined the combined effects of temperature and nitrate availability in natural sediments. Using 15 N-isotope labelling and anoxic sediment incubations, we found that temperature effects on N 2 O and N 2 production from denitrification were evident only under high nitrate levels (100 µM), while no significant temperature response occurred under low nitrate concentration (10 µM). At high nitrate availability, N 2 production increased at higher temperatures, whereas net N 2 O production declined, leading to a lower production ratio of N 2 O to N 2 at warmer temperatures. These findings suggest that in nitrogen-limited ecosystems, substrate availability plays a stronger role than temperature in regulating denitrification. More broadly, they provide insights into how nutrient loading and climate warming interact to shape nitrogen cycling and greenhouse gas emissions in aquatic ecosystems.
