自然丰度法与同位素稀释法测定植物固氮能力的比较

doi:10.7523/j.ucas.2021.0008

摘要/Abstract

摘要： 生物固氮是生态系统有效氮的重要来源，目前存在多种测定和计算方法。以青藏高原高寒草原豆科植物团垫黄芪（Astragalus arnoldii）为对象，对比自然丰度法和同位素稀释法的差异，探讨4种计算方法、4种参考植物和2个取样时间对团垫黄芪生物固氮百分率（% Ndfa）评估的影响。结果表明：参考植物的δ¹⁵N在自然生长状态下与7月份相比，8月份均显著降低（P<0.05）；施加（¹⁵NH₄）₂SO₄后，4种参考植物紫花针茅（Stipa purpurea）、高山嵩草（Kobresia pygmaea）、矮火绒草（Leontopodium nanum）和青藏苔草（Carex moorcroftii）24h取样的测定值高于30d后取样的测定值（P<0.05）。无论标记与否，团垫黄芪的¹⁵N丰度在2个采样时间都无明显差异，采用原子百分超和原子百分差这2种计算方法得到的% Ndfa也没有显著差异。除矮火绒草外，以其他3种植物以及4种植物的平均值作为参考时，采用自然丰度法计算的% Ndfa都显著高于同位素稀释法（P<0.05）。取样时间不同自然丰度法的测定结果差异显著（F=89.906，P<0.01），标记后取样时长对同位素稀释法影响显著（F=496.712，P<0.01）。

关键词: 生物固氮, 自然丰度法, 同位素稀释法, 青藏高原, 高寒草原, ¹⁵N

Abstract: Biological nitrogen fixation (BNF) is an important source of nitrogen in ecosystem, therefore, several experimental techniques and calculating methods have been developed to quantify the contribution of BNF to plants and vegetations. In this study, percentage of plant N derived from N₂-fixation (%Ndfa) was evaluated for a leguminous species, Astragalus arnoldii, in an alpine steppe in Qinghai-Tibet Plateau in order to compare two dominant in situ experimental techniques with different calculating approaches, reference plants, and sampling times. The δ¹⁵N values of four reference plants, i.e., Stipa purpurea, Kobresia pygmaea, Leontopodium nanum, and Carex moorcroftii, were significantly lower in late August than in late July (P<0.05). However, they were significantly higher in later August, 30 days after application of (¹⁵NH₄)₂SO₄ to soil, than late July which was 24h after labeling (P<0.05). In either site with or without (¹⁵NH₄)₂SO₄ application, δ¹⁵N of A. arnoldii did not differ in the two sampling times. Besides,%Ndfa of A. arnoldii did not differ between calculation based on ¹⁵N excess relative to atmospheric N₂ and that relative to unlabeled plants. Nevertheless,%Ndfa measured by natural abundance technique was significantly higher than that by isotope dilution technique (P<0.05) except for L. nanum as the reference species. The sampling time had a significant effect on estimated%Ndfa values in both the naturalabundance technique (F=89.906, P<0.01), and isotope dilution technique (F=496.712, P<0.01).

Key words: biological nitrogen fixation, natural abundance technique, isotope dilution technique, Qinghai-Tibet plateau, alpine steppe, ¹⁵N

中图分类号:

Q948.1

李润富, 牛海山, 孔倩, 刘强. 自然丰度法与同位素稀释法测定植物固氮能力的比较[J]. 中国科学院大学学报, 2022, 39(1): 34-42.

LI Runfu, NIU Haishan, KONG Qian, LIU Qiang. Comparison of natural ¹⁵N abundance technique and ¹⁵N dilution technique in the determination of plant nitrogen fixation[J]. Journal of University of Chinese Academy of Sciences, 2022, 39(1): 34-42.

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