Abstract
Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.
Highlights
Microbial ammonia oxidation is the first and rate-limiting step of nitrification, which is the only oxidative process that connects the oxidized and reduced state of inorganic nitrogen to maintain the global nitrogen cycling [1]
Our study demonstrates the differential abundance and community structure of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in paddy soils from northern China to southern China
A positive correlation was observed between the potential nitrification activity (PNA) and soil NH3 content, AOA abundance, while a negative correlation was detected between PNA and the diversity of AOB community (r = −0.81, P < 0.01)
Summary
Microbial ammonia oxidation is the first and rate-limiting step of nitrification, which is the only oxidative process that connects the oxidized and reduced state of inorganic nitrogen to maintain the global nitrogen cycling [1]. AOA has been proved to be the dominant group in nitrification in some soils [7] [8], and in some acidic soils which only AOA are detectable [6] [9], while the converse has been demonstrated in agricultural soils [10] and N-rich soils [11]. These inconsistent results raise continuous debate about the contribution of AOA and AOB to nitrification [12]. The large-scale geographic analysis of AOA and AOB population may provide intriguing hints regarding the niche differentiation of ammonia oxidizer communities and their contribution in nitrification
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