Rethinking the sub-Antarctic terrestrial N-cycle: evidence for organic N acquisition by Marion Island grasses

IF 1.5 4区环境科学与生态学 Q3 BIODIVERSITY CONSERVATION

Polar Biology Pub Date : 2024-04-02 DOI:10.1007/s00300-024-03240-1

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引用次数: 0

Abstract

Organic N (oN, e.g., amino acids) is an important N-resource for plants in soils replete with oN but not inorganic N (iN; i.e., NH₄⁺ and NO₃⁻), such as cold ecosystems with temperature-limited soil decomposition rates. However, sub-Antarctic literature assumes that plants only acquire iN, potentially underestimating plant-available N. We hypothesised that Marion Island (− 46.90°, 37.75°) grasses (Polypogon magellanicus, Poa cookii, Agrostis stolonifera and Poa annua) acquire oN and that oN relative to iN provision affects plant growth. We investigated oN and iN uptake and growth responses in two hydroponics experiments. In situ N (¹⁵N-glycine, ¹⁵NO₃⁻ and ¹⁵NH₄⁺) acquisition was investigated at three field sites with decreasing faunal influence, thus iN input and microbial activity. When plants grown in mire water were supplied with ¹⁵N-glycine or ¹⁵NO₃⁻, root δ¹⁵N enrichment was highest for glycine-supplied plants. In the second hydroponics experiment, plant N-uptake rates (nmol g biomass⁻¹ s⁻¹) were significantly higher for glycine than NO₃⁻, but relative growth rates (g g⁻¹ d⁻¹) lower on glycine. There were species-specific biomass allocation responses to N concentration (4 mM and 0.4 mM) and N-form (glycine and NO₃⁻). Glycine-supplied grasses at the low iN concentration field sites had significantly higher δ¹⁵N enrichment relative to those at sites with high iN, suggesting higher oN uptake when iN is limiting. We demonstrate the importance of accounting for oN acquisition in the sub-Antarctic. As a system with high soil oN relative to iN, plants may predominantly meet N-demands through oN rather than iN acquisition.

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反思亚南极陆地氮循环：马里恩岛禾本科植物获取有机氮的证据

摘要有机氮（oN，如氨基酸）是植物在富含 oN 但不富含无机氮（iN，即 NH4+ 和 NO3-）的土壤中的重要氮资源，例如在土壤分解速率受温度限制的寒冷生态系统中。我们假设马里恩岛（- 46.90°, 37.75°）的禾本科植物（Polypogon magellanicus、Poa cookii、Agrostis stolonifera 和 Poa annua）能获得 oN，而 oN 相对于 iN 的供应量会影响植物的生长。我们在两个水培实验中研究了 oN 和 iN 的吸收和生长反应。我们在三个田间地点调查了原位氮（15N-甘氨酸、15NO3- 和 15NH4+）获取情况，这三个地点的动物影响逐渐减弱，因此 iN 输入和微生物活动也逐渐减弱。当向沼泽水中生长的植物提供 15N 甘氨酸或 15NO3- 时，提供甘氨酸的植物根部δ15N 富集程度最高。在第二次水培实验中，植物对甘氨酸的氮吸收率（毫摩尔克生物量-1秒-1）明显高于对 NO3-的吸收率，但甘氨酸的相对生长率（克-1日-1）较低。不同物种的生物量分配对氮浓度（4 mM 和 0.4 mM）和氮形式（甘氨酸和 NO3-）有不同的反应。在低iN浓度的田间地点，提供甘氨酸的禾本科植物的δ15N富集度明显高于高iN浓度的地点，这表明当iN限制时，禾本科植物对oN的吸收率更高。我们证明了在亚南极地区考虑 oN 获取的重要性。作为一个土壤 oN 相对于 iN 较高的系统，植物可能主要通过 oN 而不是 iN 获取来满足对氮的需求。

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来源期刊

Polar Biology 生物-生态学

CiteScore

3.60

自引率

11.80%

发文量

116

审稿时长

3-8 weeks

期刊介绍： Polar Biology publishes Original Papers, Reviews, and Short Notes and is the focal point for biologists working in polar regions. It is also of interest to scientists working in biology in general, ecology and physiology, as well as in oceanography and climatology related to polar life. Polar Biology presents results of studies in plants, animals, and micro-organisms of marine, limnic and terrestrial habitats in polar and subpolar regions of both hemispheres. Taxonomy/ Biogeography Life History Spatio-temporal Patterns in Abundance and Diversity Ecological Interactions Trophic Ecology Ecophysiology/ Biochemistry of Adaptation Biogeochemical Pathways and Cycles Ecological Models Human Impact/ Climate Change/ Conservation