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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
Ecological Research ( IF 2 ) Pub Date : 2021-04-07 , DOI: 10.1111/1440-1703.12221
Xu‐Ri 1, 2 , Dongxue Dai 1, 3 , Xingliang Xu 4, 5
Affiliation  

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.

中文翻译:

青藏高原中部豆科植物和豆科植物为主的高山草原对豆科植物的共生固氮作用

固定共生N 2的植物物种出现在许多压力环境中,包括青藏高原中部,在该物种中,豆科植物小叶棘豆(Oxytropis microphylla)棘豆Oxytropis glacialis)黄芪(Astragalus arnoldii)都出现在海拔4700 m以上的高山草原上,或者作为伴侣或作为优势种,占地上草原生物量的13.91–60.25%。然而,它们在营养上对共生N 2固定的依赖程度尚不清楚。我们测量在豆类的同伴(LC)和豆科植物显性(LD)高山草原社区使用的共生固氮速率15氮同位素稀释技术。在三种豆科植物中,来自大气的氮(%Ndfa)在地上组织中为17%至61%,在地下组织中为70%至88%。基于地上生物量,LC和LD的N 2固定率估计为0.25±0.04和1.39±0.20 g N m -2 year -1。当同时考虑地上和地下组织时,LC和LD分别为0.86±0.04和2.77±0.22 gNm - 2-1。青藏高原(约0.7万公里高山草原的总生物固氮(BNF)2)然后可保守地估计在大约0.6Ť克N-年-1使用LC社区的BNF估算值。我们的研究结果表明,仅基于地上生物量和LC群落的估算值可能会严重低估豆科植物从BNF产生的N投入到高山生态系统N预算。
更新日期:2021-05-17
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