Warming Shapes <i>nirS-</i> and <i>nosZ</i> -Type Denitrifier Communities and Stimulates N ₂ O Emission in Acidic Paddy Soil

Abstract

Warming strongly stimulates soil nitrous oxide (N₂O) emission, contributing to the global warming trend. Submerged paddy soils exhibit huge N₂O emission potential; however, the N₂O emission pathway and underlying mechanisms for warming are not clearly understood. We conducted an incubation experiment using ¹⁵N to investigate the dynamics of N₂O emission at controlled temperatures (5, 15, 25, and 35°C) in 125% water-filled pore space. The community structures of nitrifiers and denitrifiers were determined via high-throughput sequencing of functional genes. Our results showed that elevated temperature sharply enhanced soil N₂O emission from submerged paddy soil. Denitrification was the main contributor, accounting for more than 90% of total N₂O emission at all treatment temperatures. N₂O flux was coordinatively regulated by <i>nirK-</i>, <i>nirS-</i>, and <i>nosZ</i>-containing denitrifiers but not ammonia-oxidizing archaea or ammonia-oxidizing bacteria. The <i>nirS</i>-containing denitrifiers were more sensitive to temperature shifts, especially at a lower temperature range (5 to 25°C), and showed a stronger correlation with N₂O flux than that of <i>nirK</i>-containing denitrifiers. In contrast, <i>nosZ</i>-containing denitrifiers exhibited substantial variation at higher temperatures (15 to 35°C), thereby playing an important role in N₂O consumption. Certain taxa of <i>nirS</i>- and <i>nosZ</i>-containing denitrifiers regulated N₂O flux, including <i>nirS</i>-containing denitrifiers affiliated with <i>Rhodanobacter</i> and <i>Cupriavidus</i> as well as <i>nosZ</i>-containing denitrifiers affiliated with <i>Azoarcus</i> and <i>Azospirillum</i>. Together, these findings suggest that elevated temperature can significantly increase N₂O emission from denitrification in submerged paddy soils by shifting the overall community structures and enriching some indigenous taxa of <i>nirS</i>- and <i>nosZ</i>-containing denitrifiers. <b>IMPORTANCE</b> The interdependence between global warming and greenhouse gas N₂O has always been the hot spot. However, information on factors contributing to N₂O and temperature-dependent community structure changes is scarce. This study demonstrated high-temperature-induced N₂O emission from submerged paddy soils, mainly via stimulating denitrification. Further, we speculate that key functional denitrifiers drive N₂O emission. This study showed that denitrifiers were more sensitive to temperature rise than nitrifiers, and the temperature sensitivity differed among denitrifier communities. N₂O-consuming denitrifiers (<i>nosZ</i>-containing denitrifiers) were more sensitive at a higher temperature range than N₂O-producing denitrifiers (<i>nirS</i>-containing denitrifiers). This study's findings help predict N₂O fluxes under different degrees of warming and develop strategies to mitigate N₂O emissions from paddy fields based on microbial community regulation.