Symbiotic nitrogen fixation in the alpine community of a lichen heath of the Northwestern Caucasus Region (the Teberda Reserve) |
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Authors: | M I Makarov T I Malysheva A A Ermak V G Onipchenko A L Stepanov O V Menyailo |
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Institution: | 1.Faculty of Soil Science,Lomonosov Moscow State University,Moscow,Russia;2.Faculty of Biology,Lomonosov Moscow State University,Moscow,Russia;3.Sukachev Institute of Forestry, Siberian Branch,Russian Academy of Sciences,Akademgorodok, Krasnoyarsk,Russia |
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Abstract: | The symbiotic fixation of atmospheric nitrogen by leguminous plants in the alpine community of a lichen heath at the Teberda
State Biosphere Reserve is well adapted to low soil temperature characteristic for the altitude of 2800 m a.s.l. For the determination
of the N fixation by isotopic methods (the method of the natural 15N abundance and the method of isotopic 15N dilution), Trifolium polyphyllum was taken as the control plant. This plant was used as it does not form symbiosis with the nitrogen-fixing bacteria in the
highlands of the Northern Caucasus Region. The contribution of the N fixation to the N nutrition of different leguminous plant
species as determined by the natural 15N abundance method amounted to 28–73% at δ15N0 = 0‰ and 46–117% at δ15N0 = −1‰; for the determination of the N fixation by the method of the isotopic label’s dilution, it was 34–97%. The best correlation
of the results obtained by these two isotopic methods was observed for the natural fractionation of the N isotopes in the
course of the N fixation in the range of −0.5 to −0.7‰. The determination of the nitrogenase activity of the roots by the
acetylene method confirmed the absence of N fixation in T. polyphyllum and its different contribution to the N nutrition of different species of leguminous plants. |
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