Distribution of ammonia oxidizers and their role in N2O emissions in the reservoir riparian zone
2022
Li, Tingting | Wang, Xiaoyan | Huang, Jingyu | Wang, Yubing | Song, Shuang
As a transitional boundary between terrestrial and aquatic ecosystems, the riparian zone is considered a hotspot for N₂O production because of the active nitrogen processes. Ammoxidation is an important microbial pathway for N₂O production, but the distribution of ammonia oxidizers under different land‐use types in the reservoir riparian zone and what role they played in N₂O emissions are still not clear. We investigated spatiotemporal distributions of ammonia‐oxidizing archaea (AOA) and bacteria (AOB) and their role in N₂O emissions in different land‐use types along the riparian zone of Miyun Reservoir: grassland, sparse woods, and woodland. We found significant differences in both AOA abundance and AOB diversity indices among land‐use types. AOA and AOB communities were significantly separated by different land‐use types. The main drivers to determine the distribution of ammonia‐oxidizing microbial community were soil water content, NH₄⁺, NO₃⁻, and total organic carbon (TOC). In situ N₂O flux was highest in woodland with a mean value of 12.28 μg/m²·h, and it was substantially decreased by 121% and 123% in sparse woods and grassland. TOC content was decreased by 20% and 40% in sparse woods and grassland compared with woodland, and it was significantly positively correlated with in situ N₂O flux. Meanwhile, AOB diversity indices were significantly correlated with in situ N₂O flux. These results showed that the heterogeneity of physicochemical properties among different land‐use types affected the community of AOA and AOB in riparian zones. AOB not AOA, and community diversity rather than abundance, played a role in N₂O emissions.
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