Distribution of ammonia oxidizers and their role in N₂O emissions in the reservoir riparian zone

Abstract

As a transitional boundary between terrestrial and aquatic ecosystems, the riparian zone is considered a hotspot for N 2 O production because of the active nitrogen processes. Ammoxidation is an important microbial pathway for N 2 O production, but the distribution of ammonia oxidizers under different land-use types in the reservoir riparian zone and what role they played in N 2 O emissions are still not clear. We investigated spatiotemporal distributions of ammonia-oxidizing archaea (AOA) and bacteria (AOB) and their role in N 2 O 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, NH 4 + , NO 3 − , and total organic carbon (TOC). In situ N 2 O flux was highest in woodland with a mean value of 12.28 μg/m 2 •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 N 2 O flux. Meanwhile, AOB diversity indices were significantly correlated with in situ N 2 O 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 N 2 O emissions.

N2O consumption, uptake, and microbial reduction processes in flooded sandy loamy paddy soils

“…Numerous studies have shown that soils with higher sand content (i.e., larger soil pores) have higher N 2 O emissions (Ding et al., 2019; Mangalassery et al., 2013; Zhang et al., 2021). For example, the riparian zone at the land–water interface is often considered a hot spot for N 2 O production due to its active nitrogen processes (Li et al., 2022). However, other studies have shown that the riparian zone, as a buffer zone between aquatic and terrestrial ecosystems, has a high N 2 O reduction potential (Zhao et al., 2022).…”