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

Wen Zhou,Bei Lu,Xiaoliang Jiang,Jian Ouyang,Guihua Liu,Wenzhi Liu

doi:10.3390/microorganisms8060933

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.

Highlights

Nitrification is the biological oxidation of ammonia into nitrate [1] and it plays essential roles in the wetland nitrogen cycle and N2O production
Our results indicated that the ammonia-oxidizing bacteria (AOB) communities in the Qinghai–Tibetan Plateau were more sensitive to changes in local environments than the ammonia-oxidizing archaea (AOA) communities, which was consistent with other studies in Yangtze River [55] and in East Asian paddy soils [74]
The compositions and structures of AOA and AOB communities are of importance to the nitrification

Summary

Introduction

Nitrification is the biological oxidation of ammonia into nitrate [1] and it plays essential roles in the wetland nitrogen cycle and N2O production. Two previous studies have investigated ammonia-oxidizer communities in the overlying water and sediments of five rivers in the Qinghai–Tibetan Plateau, and found that the high-elevation conditions (low temperature, low ammonium concentration, and intensive solar radiation) shaped distinctive community compositions and distribution patterns for ammonia oxidizers in the five rivers, as compared with low-elevation rivers [10,16]. These observations highlight the necessity of better understanding how a wider range environmental condition can regulate ammonia-oxidizer communities. It is unknown whether these findings are applicable to other high-elevation wetlands

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Results

Discussion

Conclusion