Biological controls over the abundances of terrestrial ammonia oxidizers

Aim: Ammonia-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.
Location: World-wide.
Time period: 2005-2016.
Major taxa studied: Ammonia-oxidizing archaea and ammonia-oxidizing bacteria. 
Methods: A meta-analysis and synthesis was 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 mycorrhiz...