Effect of restoration types on the community structure of microbes harboring nifH and chiA genes in alpine meadow

doi:10.13287/j.1001-9332.202112.040

Abstract

Abstract: Biological nitrogen (N) fixation and organic N degradation are the main sources of soil available N, while microorganisms driving such processes play an important role in soil N supply and the maintenance of soil fertility. In this study, real-time quantitative PCR and amplicon sequencing technology were used to examine the effects of restoration types on the community structure of N₂-fixing and chitin-degrading bacteria harboring nifH and chiA genes, respectively, and the gene abundance under four meadows (undisturbed, grazing, fencing, and fencing + reseeding mea-dows) in Qinghai-Tibet Plateau. The results showed that the abundance of nifH and chiA in the four meadows followed the order of undisturbed meadow > grazed meadow > fencing meadow > fencing + reseeding meadow. The abundance of nifH and chiA in the undisturbed meadow was 3.4-6.3 times and 3.3-8.3 times of that in the other three meadows. The α diversity of N₂-fixing bacteria in gra-zing, fencing, and fencing + reseeding meadows was significantly higher than that in the undisturbed meadow, while the α diversity of chitin-degrading bacteria was higher in the undisturbed and grazing meadows. Grazing significantly increased the relative abundance of Proteobacteria, but decreased the relative abundance of Cyanobacteria and Actinobacteria. The abundance of nifH and chiA was significantly affected by soil moisture, nutrients, and vegetation characteristics, while the community structure of nifH and chiA was affected by soil moisture, soil organic carbon content, and soil pH. Compared with undisturbed meadow, grazing reduced the potential of N fixation and organic N degradation.The improvement of 10 years grazing prohibition with fencing and reseeding measures on the function of N fixation and organic N degradation was not obvious. The characteristics of functional microbes and their influencing factors should be comprehensively considered during meadow restoration, which might take longer time or take reasonable management measures to restore grazing meadow to undisturbed level.

Key words: fencing and grazing prohibition, N₂-fixing bacteria, chitin-degrading bacteria, nifH gene, chiA gene, organic nitrogen degradation

ZHANG Lu, WANG Jie, WANG Xiang-tao, LIAO Li-rong, WAN Qian, LIU Guo-bin, ZHANG Chao. Effect of restoration types on the community structure of microbes harboring nifH and chiA genes in alpine meadow[J]. Chinese Journal of Applied Ecology, 2021, 32(12): 4349-4358.

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