Background The 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). Methods The 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). Results nosZ-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).

Background: The Hailuogou Glacier in the Gongga Mountain region (SW China), on the southeastern edge of the Tibetan Plateau, is well known for its low-elevation modern glaciers. Since the end of the Little Ice Age (LIA), the Hailuogou Glacier has retreated continuously due to global warming, primary vegetation succession and soil chronosequence have developed in this retreat area. The retreated area of Hailuogou Glacier has not been strongly disturbed by human activities, thus it is an ideal models for exploring the biological colonization of nitrogen in the primary successional stages of ecosystem. The nosZ gene encodes the catalytic center of nitrous oxide reductase and is an ideal molecular marker in studying the variation in the denitrifying bacterial community. Methods: Soil properties as well as abundance and composition of the denitrifying bacterial community were determined via chemical analysis, quantitative polymerase chain reaction (qPCR), and terminal restriction fragment length polymorphism (T-RFLP), respectively. The relationships between the nosZ denitrifying bacterial community and soil properties were determined using redundancy analysis (RDA). Soil properties, potential denitrify activity (PDA), and the nitrous oxide reductase gene (nosZ)-denitrifying bacterial communities significantly differed among successional stages. Results: Soil properties, potential denitrify activity (PDA), and the nitrous oxide reductase gene (nosZ)-denitrifying bacterial communities significantly differed among successional stages. Soil pH in the topsoil decreased from 8.42 to 7.19 in the course of primary succession, while soil organic carbon (SOC) and total nitrogen (TN) gradually increased with primary succession. Available phosphorus (AP) and available potassium (AK), as well as potential denitrify activity (PDA), increased gradually and peaked at the 40-year-old site. The abundance of the nosZ denitrifying bacterial community followed a similar trend. The variation in the denitrifying community composition was complex; Mesorhizobium dominated the soil in the early successional stages (0-20 years) and in the mature phase (60 years), with a relative abundance greater than 55%. Brachybacterium was increased in the 40-year-old site, with a relative abundance of 62.74%, while Azospirillum dominated the early successional stages (0-20 years). Redundancy analysis (RDA) showed that the nosZ denitrifying bacterial community correlated with soil available phosphorus and available potassium levels (P < 0.01).

Background: The Hailuogou Glacier in the Gongga Mountain region (SW China), on the southeastern edge of the Tibetan Plateau, is well known for its low-elevation modern glaciers. Since the end of the Little Ice Age (LIA), the Hailuogou Glacier has retreated continuously due to global warming, primary vegetation succession and soil chronosequence have developed in this retreat area. The retreated area of Hailuogou Glacier has not been strongly disturbed by human activities, thus it is an ideal models for exploring the biological colonization of nitrogen in the primary successional stages of ecosystem. The nosZ gene encodes the catalytic center of nitrous oxide reductase and is an ideal molecular marker in studying the variation in the denitrifying bacterial community. Methods: Soil properties as well as abundance and composition of the denitrifying bacterial community were determined via chemical analysis, quantitative polymerase chain reaction (qPCR), and terminal restriction fragment length polymorphism (T-RFLP), respectively. The relationships between the nosZ denitrifying bacterial community and soil properties were determined using redundancy analysis (RDA). Soil properties, potential denitrify activity (PDA), and the nitrous oxide reductase gene (nosZ)-denitrifying bacterial communities significantly differed among successional stages. Results: Soil properties, potential denitrify activity (PDA), and the nitrous oxide reductase gene (nosZ)-denitrifying bacterial communities significantly differed among successional stages. Soil pH in the topsoil decreased from 8.42 to 7.19 in the course of primary succession, while soil organic carbon (SOC) and total nitrogen (TN) gradually increased with primary succession. Available phosphorus (AP) and available potassium (AK), as well as potential denitrify activity (PDA), increased gradually and peaked at the 40-year-old site. The abundance of the nosZ denitrifying bacterial community followed a similar trend. The variation in the denitrifying community composition was complex; Mesorhizobium dominated the soil in the early successional stages (0-20 years) and in the mature phase (60 years), with a relative abundance greater than 55%. Brachybacterium was increased in the 40-year-old site, with a relative abundance of 62.74%, while Azospirillum dominated the early successional stages (0-20 years). Redundancy analysis (RDA) showed that the nosZ denitrifying bacterial community correlated with soil available phosphorus and available potassium levels (P < 0.01).