Dorsaf Kerfahi;Yu Shi;Baozhan WANG;Huacan Song;Haiyan Chu;Jonathan M. Adam

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China);School of Natural Sciences, Department of Biological Sciences, Keimyung University, Daegu 42601 (Republic of Korea);Key Lab of Microbiology for Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095 (China);State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China); University of Chinese Academy of Sciences, Beijing 101408 (China);School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210008 (China;State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, Henan 475001 (China);Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL (United Kingdom)

amoA gene;ammonia-oxidizing bacteria;assembly processes;beta nearest taxon index;community structure;operational taxonomic unit;OXIDATION;NICHE;PH;DIVERSITY;BACTERIA;NITRIFICATION;ABUNDANCE;SEDIMENTS;SCAL

Archaeal ammonia oxidizers (AOA) are important in converting ammonia into nitrates in soils. While many aspects of their community structure have been studied, the relative importance of stochastic versus deterministic processes has been poorly understood. We compared AOA communities across the North China Plain, targeting the amoA gene. A phylogenetic null modelling approach was used to calculate beta-nearest taxon index (beta-NTI) to quantify the influence of stochastic and deterministic processes. We found that spatial distance between samples predicted the perceived processes involved in community structuring, with stochastic processes dominating at more local scales. At greater distances, stochasticity became weaker. However, differences in soil pH – which were also the strongest determinant of AOA community – were a much stronger predictor of the community structuring, leaving distance effects redundant as an explanation of community structuring processes. AOA communities differing by less than 1 pH unit differ mainly stochastically in terms of OTU composition. At larger pH differences, deterministic processes based on heterogeneous selection between clades become increasingly dominant. It appears that AOA community composition is largely determined by environment. The exception is amongst very similar pH environments, whether spatially near or far, in which stochastic effects dominate in causing differences in community composition.