Influences of nitrogen forms on abundances and community structures of ammonia and nitrite oxidizers in a slightly alkaline upland soil

Abstract

ABSTRACT Nitrogen addition can significantly affect soil nitrification capacity through driving soil nitrifiers. However, the roles of nitrogen forms on nitrifiers are rarely known. This study assessed the effects of nitrogen addition forms (NH4 +-N and NO3 –-N) on nitrifiers’ abundances and community structures in a slightly alkaline upland soil by means of a short-term microcosms experiment. Nitrospira-like nitrite-oxidizing bacteria (NOB) numerically dominated nitrifiers’ community. Ammonia-oxidizing archaea (AOA) abundance positively correlated to Nitrospira-like NOB abundance, and ammonia-oxidizing bacteria (AOB) abundance positively linked to Nitrobacter-like NOB abundance. NH4 +-N addition significantly increased AOB and Nitrobacter-like NOB abundances, whereas the abundances of tested four groups of nitrifiers were relatively insensitive to NO3 –-N addition. AOA and Nitrobacter-like NOB community structures were significantly changed only upon NH4 +-N addition, but AOB and Nitrospira-like NOB community structures were obviously altered by both NH4 +-N and NO3 –-N addition, with stronger impacts by the former. Overall, our results confirmed that not only NH4 +-N but also NO3 –-N addition obviously affected soil nitrifiers’ community. The findings obtained here highlight distinct physiological potentials of nitrifiers’ subgroups to upland soil nitrification.