Biological controls over the abundances of terrestrial ammonia oxidizers

Abstract

AimAmmonia‐oxidizing archaea (AOA) and bacteria (AOB) are the primary agents for nitrification, converting ammonia (NH4+) into nitrate (NO3−) and modulating plant nitrogen (N) utilization and terrestrial N retention. However, there is still lack of a unifying framework describing the patterns of global AOA and AOB distribution. In particular, biotic interactions are rarely integrated into any of the conceptual models.LocationWorld‐wide.Time period2005–2016.Major taxa studiedAmmonia‐oxidizing archaea and ammonia‐oxidizing bacteria.MethodsA meta‐analysis and synthesis were conducted to obtain a general picture of global AOA and AOB distribution and identify the primary driving factors. A microcosm experiment was then conducted to assess effects of relative carbon to nitrogen availability for heterotrophic microbes on AOA and AOB in two distinct soils. A mesocosm experiment was further carried out to characterize the effects of plant roots and their arbuscular mycorrhizal fungi (AMF) on AOA and AOB abundances using hyphae‐ or root‐ingrowth techniques.ResultsOur meta‐analysis showed that soil carbon to nitrogen (C/N) ratios explained the most variance in AOA and AOB abundances, although soil pH had a significant effect. Experimental results demonstrated that high cellulose and mineral N inputs increased total microbial biomass and microbial activities, but inhibited AOA and AOB, suggesting microbial inhibition of AOA and AOB. Also, AMF and roots suppressed AOA and AOB, respectively.Main conclusionsOur study provides convincing evidence illustrating that relative carbon to nitrogen availability can predominantly affect the abundances of AOA and AOB. Our experimental results further validate that biotic competition among plants, heterotrophic microbes and ammonia oxidizers for substrate N is the predominant control upon AOA and AOB abundances. Together, these findings provide new insights into the role of abiotic and biotic factors in modulating terrestrial AOA and AOB abundances and their potential applications for management of nitrification in an increasing reactive N world.

Global gross nitrification rates are dominantly driven by soil carbon‐to‐nitrogen stoichiometry and total nitrogen

“…Our study also revealed that GAN, which uses NH 4 + as a substrate mainly by AOB and AOA (Zhang et al, 2014), is predominantly controlled by C:N (Figure S4), which has a negative correlation with AOA and AOB abundances (Xiao et al, 2021). In soils with high C:N, low N availability is the main limiting factor to AOA and AOB due to strong competition from heterotrophic microbes (Xiao et al, 2020). In the same context, our results emphasized the importance of soil total N in regulating GN, which is in line with findings by Wang et al (2018).…”

Environmental adaptation is stronger for abundant rather than rare microorganisms in wetland soils from the Qinghai‐Tibet Plateau

“…The key role of soil ammonia nitrogen in governing both rare and abundant bacterial and fungal community assembly processes might be partially attributed to the functions of nitrogenous nutrients and the physicochemical characteristics of bacteria and fungi (Zhong et al, 2020). Ammonia nitrogen is an important nutrient for plant and microbial growth (Blázquez et al, 2017), and plays an important role in regulating soil nitrogen cycling and nitrogen‐cycling‐related microbial communities (Ma et al, 2020; Xiao et al, 2020). Moreover, ammonia nitrogen is closely correlated with soil bulk density, which in turn affects gas diffusion (e.g., oxygen and carbon dioxide) and microbial activity (Pan et al, 2018).…”

Inter-microbial competition for N and plant NO3− uptake rather than BNI determines soil net nitrification under intensively managed Brachiaria humidicola

“…Hence, it could be speculated that the plant-dependent reduction of nitrifier populations was due to increased inter-microbial competition between bacterial heterotrophs (stimulated by the plant) and nitrifiers. A possible explanation for the latter theory would be long-term competition for substrate N, proposed to be the predominant control of ammonia oxidizer abundance (Xiao et al 2020). In our experiment, especially the concomitant reduction of amoA and archaeal 16S rRNA gene abundances favors the conceptualized theory of intermicrobial competition (Fig.…”