Abstract
Asymbiotic nitrogen-fixing (ANF) bacteria contribute a substantial amount of nitrogen in ecosystems, especially in those with low symbiotic nitrogen fixation (SNF) capability. Degradation of alpine grassland is widespread on the Tibetan Plateau and sown grassland has become one of the main strategies for grassland restoration. However, the diversity and community structure of ANF bacteria in different grassland types remain unknown. The aim of this study was to fill this gap. Soil samples were obtained from 39 grassland plots selected from three counties in the eastern Tibetan Plateau. The plots were classified as natural grassland (NG), sown grassland (SG), lightly degraded grassland (LDG), and severely degraded grassland (SDG). ANF microbial communities of the four grassland types were compared at the level of community and species diversity by 16S rRNA high-throughput sequencing technology. The phylum Proteobacteria accounted for >72% of the ANF bacteria. The community structures of soil ANF bacteria differed significantly (p < 0.01) among grassland types. We concluded that: (1) planting gramineous forage could possibly mitigate the decrease in diversity of soil ANF bacteria caused by grassland degradation; and (2) the diversity of soil ANF bacteria in alpine grassland of the Tibetan Plateau is closely related to grassland degradation and restoration.
Highlights
Biological nitrogen fixation, a process in which some prokaryotic microorganisms reduce atmospheric nitrogen molecules to ammonia through the catalytic action of nitrogenase (Dart and Wani, 1982; Cleveland et al, 1999), is the main natural input form of nitrogen in ecosystems (Barron et al, 2009; Reed et al, 2011; Zheng et al, 2018)
Known asymbiotic nitrogen fixation (ANF) microorganisms were identified from the sequencing results, and the data were analyzed
There were 109 operational taxonomic units (OTUs) species shared by the four grassland types, while 51 and 23 OTUs species were endemic to natural grassland (NG) and sown grassland (SG), respectively
Summary
Biological nitrogen fixation, a process in which some prokaryotic microorganisms reduce atmospheric nitrogen molecules to ammonia through the catalytic action of nitrogenase (Dart and Wani, 1982; Cleveland et al, 1999), is the main natural input form of nitrogen in ecosystems (Barron et al, 2009; Reed et al, 2011; Zheng et al, 2018). Based on the interaction between microorganisms and plants, biological nitrogen-fixation can be divided into symbiotic nitrogen fixation (SNF), free-living nitrogen fixation and associative nitrogen fixation. The latter two are collectively referred to as asymbiotic nitrogen fixation (ANF) (Bottomley and Myrold, 2015). Studies indicated that there are many factors affecting the community structure of nitrogen-fixing bacteria, including altitude and soil organic carbon, pH, and total nitrogen content (Limmer and Drake, 1996; Pérez et al, 2004; Zhang et al, 2006; Wang et al, 2017; Zheng et al, 2018; Bomfim et al, 2019)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
