Contrasting effects of nitrogen forms and soil pH on ammonia oxidizing microorganisms and their responses to long-term nitrogen fertilization in a typical steppe ecosystem

Abstract

Ammonia-oxidizing microorganisms, i.e. ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), are the primary agents responsible for soil nitrification. Few studies, however, have evaluated how AOA and AOB responses to long-term N fertilization are affected by soil pH and different forms of nitrogen (N). We examined the effects of soil acidification and different forms of N (NH4+ and NO3−) on abundances and community structure of AOA and AOB based on a field acid addition experiment and a short-term microcosm N addition experiment. The field acid addition experiment demonstrated that, with decreasing soil pH, AOB abundance decreased while AOA abundance mostly increased except ..