Ammonium availability and pH control the contributions of ammonia- oxidizing bacteria and archaea to nitrification

Abstract

Abstract Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) control nitrification in terrestrial systems. Soil pH and substrate availability (NH4+) influence community composition, which may affect the contributions of these organisms to nitrification in forest soils. We identified the amoA of AOA and AOB from northern hardwood stands that represent a natural gradient of nitrification, soil pH, and net N mineralization (i.e., NH4 + availability). Specifically, we investigated (1) the responses of relative abundance and composition of AOA and AOB communities to soil pH and net N mineralization, and (2) how community composition was linked to nitrification. Soil pH was a stronger driver of AOA and AOB relative abundance than was NH4+ availability. Generally, AOA and AOB community turnover were positively associated with soil pH; however, many AOA ASVs displayed a negative association. Interestingly, the relative abundance of only a small number of AOA and AOB ASVs were significantly associated with nitrification. Our findings reveal that coexisting taxa and groups of ammonia-oxidizers in forest soils have diverse responses to environmental factors, which influence how soil microbial communities are structured, having direct implications for nitrification and the regulation of N cycling in forest systems.