Summary Nitrogen (N) uptake by plant roots from soil is the largest flux within the terrestrial N cycle. Despite its significance, a comprehensive analysis of plant uptake for inorganic and organic N forms across grasslands is lacking. Here we measured in situ plant uptake of 13 inorganic and organic N forms by dominant species along a 3000 km transect spanning temperate and alpine grasslands. To generalize our experimental findings, we synthesized data on N uptake from 60 studies encompassing 148 plant species world‐wide. Our analysis revealed that alpine grasslands had faster NH4+ uptake than temperate grasslands. Most plants preferred NO3− (65%) over NH4+ (24%), followed by amino acids (11%). The uptake preferences and uptake rates were modulated by soil N availability that was defined by climate, soil properties, and intrinsic characteristics of the N form. These findings pave the way toward more fully understanding of N cycling in terrestrial ecosystems, provide novel insights into the N form‐specific mechanisms of plant N uptake, and highlight ecological consequences of chemical niche differentiation to reduce competition between coexisting plant species.

中文翻译：

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土壤中的氮有效性控制植物对不同形式的氮的吸收


摘要 植物根系从土壤中吸收的氮 （N） 是陆地氮循环中最大的通量。尽管它很重要，但缺乏对草原植物对无机和有机氮形式的吸收的全面分析。在这里，我们测量了优势物种在横跨温带和高山草原的 3000 公里样带上对 13 种无机和有机氮形式的原位植物吸收。为了概括我们的实验结果，我们综合了来自全球 60 项研究的 148 种氮吸收数据，涵盖 148 种植物。我们的分析表明，高山草原对 NH4+ 的吸收比温带草原快。大多数植物更喜欢 NO3− （65%） 而不是 NH4+ （24%），其次是氨基酸 （11%）。吸收偏好和吸收率受土壤氮有效性的调节，土壤氮有效性由气候、土壤特性和 N 形式的内在特性定义。这些发现为更全面地了解陆地生态系统中的氮循环铺平了道路，为植物氮吸收的 N 形式特异性机制提供了新的见解，并强调了化学生态位分化的生态后果，以减少共存植物物种之间的竞争。