Environmental Factors, More Than Spatial Distance, Explain Community Structure of Soil Ammonia-Oxidizers in Wetlands on the Qinghai–Tibetan Plateau

Abstract

In wetland ecosystems, ammonia oxidation highly depends on the activity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), which are, therefore, important for studying nitrogen cycling. However, the ammonia-oxidizer communities in the typical high-elevation wetlands are poorly understood. Here, we examined ammonia-oxidizer communities in soils from three wetland types and 31 wetland sites across the Qinghai–Tibetan Plateau. The amoA gene of AOA and AOB was widespread across all wetland types. Nitrososphaera clade (Group I.1b) overwhelmingly dominated in AOA community (90.36%), while Nitrosospira was the principal AOB type (64.96%). The average abundances of AOA and AOB were 2.63 × 104 copies g−1 and 9.73 × 103 copies g−1. The abundance of AOA amoA gene was higher in riverine and lacustrine wetlands, while AOB amoA gene dominated in palustrine wetlands. The environmental conditions, but not spatial distance, have a dominant role in shaping the pattern of ammonia-oxidizer communities. The AOA community composition was influenced by mean annual temperature (MAT) and mean annual precipitation (MAP), while MAT, conductivity and plant richness, pH, and TN influenced the AOB community composition. The net nitrification rate had a significant correlation to AOB, but not AOA abundance. Our results suggest a dominant role for climate factors (MAT and MAP) in shaping community composition across a wide variety of wetland sites and conditions.

Response of Sediment Microbial Communities to the Rural Wastewater in the Pond-Ditch Circulation System

“…One-way ANOVA with Turkey's post hoc tests were performed to analyze the differences in water quality, sediment physic-chemical parameters, α-diversity and richness indices of sediment bacteria, root exudates in these two systems. Sediment bacterial community richness (presented as observed species and goods coverage) and α-diversity (presented as Chao 1, Simpson, and Shannon) in rhizosphere and non-rhizosphere microenvironments in these two systems were calculated in R version 3.5.2 using the vegan package (Zhou et al, 2020). Spearman's correlation coefficients were calculated to determine the associations among sediment microbial diversity, water quality, sediment properties, and root exudates.…”

The Diversity and Community Assembly Process of Wetland Plants from Lakeshores on the Qinghai-Tibetan Plateau

“…Whereas, if absolute βNTI or βNRI values are < 2, and absolute RC bray values are < 0.95, the community assembly was treated as an "undominated" pattern, that is, no single process drove the variation in the community composition [42,43]. The Mantel test with 999 permutations was used to investigate the relationships between sample ordination on taxonomic (Bray-Curtis distance) and geographic distance and environmental similarity (Euclidean distance) [16]. The variation partitioning analysis (VPA) is widely used in ecological research to evaluate the relative contribution of the pure effects of geospatial variables (the effects of potential dispersal limitation) and the pure effects of environmental factors (deterministic process) [44][45][46].…”

“…Three subplots (1 m × 1 m) were randomly established within a plot, and all vascular plant species were recorded. The species richness for each subplot was estimated as the total number of recorded vascular plant species and the coverages were estimated visually [16]. Surface soils (0-5 cm) on each lakeshore were sampled with a 5 cm diameter hand corer.…”

“…In fact, increasing numbers of researchers have provided evidence that both deterministic and stochastic processes are supposed to jointly structure the community assembly. Consequently, the central debate has been transferred to the relative contribution of the neutral and deterministic processes in community composition and maintaining [14][15][16].…”

“…The Qinghai-Tibetan Plateau (QTP) is the largest high-altitude wetland region on the earth, and one of the most sensitive regions to changing environments [16,27]. Given the rapid and continuous speciation and diversification of plants caused by relatively rapid and uniform geological uplift, and a lesser influence by human activities, the QTP is an appropriate and unique region to detect the potential processes and mechanisms underlying biodiversity [28].…”