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The symbiotic nitrogen fixation by legumes in a legume‐companion and a legume‐dominant alpine steppe on the central Tibetan Plateau

The symbiotic nitrogen fixation by legumes in a legume‐companion and a legume‐dominant alpine... Symbiotic N2‐fixing plant species occur in many stressful environments, including the central Tibetan Plateau, where the legume species Oxytropis microphylla, Oxytropis glacialis, Astragalus arnoldii occur in the alpine steppe at elevations as high as 4700 m above sea level, either as companion or as dominant species, accounting for 13.91–60.25% of the total aboveground steppe biomass. However, the degree to which they are nutritionally reliant upon symbiotic N2 fixation is still unclear. We measured the symbiotic nitrogen fixation rate in a legume‐companion (LC) and a legume‐dominant (LD) alpine steppe community using the 15N isotope dilution technique. The N derived from the atmosphere (%Ndfa) in the three legume species ranged from 17% to 61% in aboveground tissues and from 70% to 88% in belowground tissues. The N2 fixation rate was estimated to be 0.25 ± 0.04 and 1.39 ± 0.20 g N  m−2 year−1 for LC and LD based on the aboveground biomass. It was 0.86 ± 0.04 and 2.77 ± 0.22 gNm−2 year−1 for LC and LD, respectively, when both above and belowground tissues were considered. The total biological nitrogen fixation (BNF) of the alpine steppe on the Tibetan Plateau (ca. 0.7 million km2) can then be conservatively estimated at approximately 0.6 T g N year−1 using the BNF estimate from the LC community. Our findings indicate that estimates based solely on aboveground biomass and LC communities might drastically underestimate the N inputs arising from BNF by legumes to the alpine ecosystem N budget. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecological Research Wiley

The symbiotic nitrogen fixation by legumes in a legume‐companion and a legume‐dominant alpine steppe on the central Tibetan Plateau

Ecological Research , Volume 36 (3) – May 1, 2021

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Publisher
Wiley
Copyright
© 2021 The Ecological Society of Japan
ISSN
0912-3814
eISSN
1440-1703
DOI
10.1111/1440-1703.12221
Publisher site
See Article on Publisher Site

Abstract

Symbiotic N2‐fixing plant species occur in many stressful environments, including the central Tibetan Plateau, where the legume species Oxytropis microphylla, Oxytropis glacialis, Astragalus arnoldii occur in the alpine steppe at elevations as high as 4700 m above sea level, either as companion or as dominant species, accounting for 13.91–60.25% of the total aboveground steppe biomass. However, the degree to which they are nutritionally reliant upon symbiotic N2 fixation is still unclear. We measured the symbiotic nitrogen fixation rate in a legume‐companion (LC) and a legume‐dominant (LD) alpine steppe community using the 15N isotope dilution technique. The N derived from the atmosphere (%Ndfa) in the three legume species ranged from 17% to 61% in aboveground tissues and from 70% to 88% in belowground tissues. The N2 fixation rate was estimated to be 0.25 ± 0.04 and 1.39 ± 0.20 g N  m−2 year−1 for LC and LD based on the aboveground biomass. It was 0.86 ± 0.04 and 2.77 ± 0.22 gNm−2 year−1 for LC and LD, respectively, when both above and belowground tissues were considered. The total biological nitrogen fixation (BNF) of the alpine steppe on the Tibetan Plateau (ca. 0.7 million km2) can then be conservatively estimated at approximately 0.6 T g N year−1 using the BNF estimate from the LC community. Our findings indicate that estimates based solely on aboveground biomass and LC communities might drastically underestimate the N inputs arising from BNF by legumes to the alpine ecosystem N budget.

Journal

Ecological ResearchWiley

Published: May 1, 2021

Keywords: ; ; ; ;

References