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| Titel |
High diversity of nitrogen-fixing bacteria in the upper reaches of the Heihe River, northwestern China |
| VerfasserIn |
X. S. Tai, W. L. Mao, G. X. Liu, T. Chen, W. Zhang, X. K. Wu, H. Z. Long, B. G. Zhang, Y. Zhang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 8 ; Nr. 10, no. 8 (2013-08-21), S.5589-5600 |
| Datensatznummer |
250085305
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| Publikation (Nr.) |
 copernicus.org/bg-10-5589-2013.pdf |
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| Zusammenfassung |
| Vegetation plays a key role in water conservation in the southern Qilian
Mountains (northwestern China), located in the upper reaches of the Heihe
River. Nitrogen-fixing bacteria are crucial for the protection of the
nitrogen supply for vegetation in the region. In the present study, nifH gene
clone libraries were established to determine differences between the
nitrogen-fixing bacterial communities of the Potentilla parvifolia shrubland and the Carex alrofusca meadow in
the southern Qilian Mountains. All of the identified nitrogen-fixing
bacterial clones belonged to the Proteobacteria. At the genus level,
Azospirillum was only detected in the shrubland soil, while Thiocapsa,
Derxia, Ectothiorhodospira, Mesorhizobium, Klebsiella, Ensifer, Methylocella and Pseudomonas were only
detected in the meadow soil. The phylogenetic tree was divided into five
lineages: lineages I, II and III mainly contained nifH sequences obtained from
the meadow soils, while lineage IV was mainly composed of nifH sequences
obtained from the shrubland soils. The Shannon–Wiener index of the nifH genes
ranged from 1.5 to 2.8 and was higher in the meadow soils than in the
shrubland soils. Based on these analyses of diversity and phylogeny, the
plant species were hypothesised to influence N cycling by enhancing the
fitness of certain nitrogen-fixing taxa. The number of nifH gene copies and colony-forming units
(CFUs) of the cultured nitrogen-fixing bacteria were lower in the meadow soils than
in the shrubland soils, ranging from 0.4 × 107 to 6.9 × 107 copies g−1 soil and
0.97 × 106 to 12.78 × 106 g−1 soil, respectively. Redundancy analysis (RDA) revealed
that the diversity and number of the nifH gene copies were primarily correlated
with aboveground biomass in the shrubland soil. In the meadow soil, nifH gene
diversity was most affected by altitude, while copy number was most impacted
by soil-available K. These results suggest that the nitrogen-fixing
bacterial communities beneath Potentilla were different from those beneath Carex. |
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