Abstract
BackgroundThe Hailuogou Glacier is located at the Gongga Mountain on the southeastern edge of the Tibetan Plateau, and has retreated continuously as a result of global warming. The retreat of the Hailuogou Glacier has left behind a primary succession along soil chronosequences. Hailuogou Glacier’s retreated area provides an excellent living environment for the colonization of microbes and plants, making it an ideal model to explore plant successions, microbial communities, and the interaction of plants and microbes during the colonization process. However, to date, the density of the nitrogen cycling microbial communities remain unknown, especially for denitrifiers in the primary succession of the Hailuogou Glacier. Therefore, we investigated the structural succession and its driving factors for denitrifying bacterial communities during the four successional stages (0, 20, 40, and 60 years).MethodsThe diversity, community composition, and abundance of nosZ-denitrifiers were determined using molecular tools, including terminal restriction fragment length polymorphism and quantitative polymerase chain reactions (qPCR).ResultsnosZ-denitrifiers were more abundant and diverse in soils from successional years 20–60 compared to 0–5 years, and was highest in Site3 (40 years). The denitrifying bacterial community composition was more complex in older soils (40–60 years) than in younger soils (≤20 years). The terminal restriction fragments (T-RFs) of Azospirillum (90 bp) and Rubrivivax (95 bp) were dominant in soisl during early successional stages (0–20 years) and in the mature phase (40–60 years), respectively. Specific T-RFs of Bradyrhizobium (100 bp) and Pseudomonas (275 bp) were detected only in Site3 and Site4, respectively. Moreover, the unidentified 175 bp T-RFs was detected only in Site3. Of the abiotic factors that were measured in this study, soil available phosphorus, available potassium and denitrifying enzyme activity (DEA) correlated significantly with the community composition of nosZ-denitrifiers (P < 0.05 by Monte Carlo permutation test within RDA analysis).
Highlights
Global warming has accelerated the retreat of glaciers, which has resulted in the exposure of soil and rocks that were once covered in ice (Schmidt et al, 2016)
We found that the variation in soil properties, denitrifying enzyme activity, abundance, and composition of the nosZ denitrifying bacterial community differed along successional stages
Soil pH decreased gradually in the course of succession, while soil organic carbon (SOC) and total nitrogen (TN) significantly increased with the primary succession, and available phosphorus (AP) and AK increased gradually and peaked at Site3.The diversity and abundance of nosZ -denitrifiers was higher in successional 20–60 years soils compared to successional 0–5 years soils, and was highest at Site3 (40 years)
Summary
Global warming has accelerated the retreat of glaciers, which has resulted in the exposure of soil and rocks that were once covered in ice (Schmidt et al, 2016). In this nitrogen (N) poor environment, microbes are usually the first colonizers and keystone players, especially in many pristine environments, including glacier retreat areas (Bradley et al, 2016). Previous studies have shown that the composition of soil microbial communities exhibit distinct patterns at different succession stages along retreating glaciers (Knelman et al, 2012; Schmidt et al, 2016; Insam et al, 2017). Of the abiotic factors that were measured in this study, soil available phosphorus, available potassium and denitrifying enzyme activity (DEA) correlated significantly with the community composition of nosZ -denitrifiers (P < 0.05 by Monte Carlo permutation test within RDA analysis)
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