Seed germination plays an important role in mediating plant species composition of grassland communities under nitrogen (N) enrichment. Shifts of plant community structure with N‐enhanced deposition in terrestrial ecosystems have occurred globally. Despite numerous studies about the effects of enhanced N deposition on mature plant communities, few studies have focused on seed germination. Using a laboratory experiment, we report the effects of five N concentrations, including 0, 5, 10, 20, and 40 mM N (NH₄NO₃) on seed germination of eight semi‐arid grassland species. Results showed that low N concentrations (5‐ and 20‐mM N) promoted mean final germination proportion of all eight species by 4.4% and 6.4%, but high concentrations (40 mM N) had no effect. The mean germination rate was decreased 2.1% and 5.1% by higher N concentration (20‐ and 40‐mM N) levels, but germination start time showed the opposite trend, delayed by 0.7, 0.9, and 1.8 d for the 10, 20, and 40 mM N treatments. Final germination proportion, mean germination rate, and germination start time were significantly different among species in response to N concentration treatments. The final germination proportion of Allium tenuissimum and Chenopodium glaucum were suppressed by increased N concentration, whereas it increased for Potentilla bifurca, Plantago asiatica, and Setaria viridis. Our findings provide novel insights into N deposition‐induced species loss based on seed germination factors in semi‐arid grassland communities.

中文翻译：

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氮添加对八种半干旱草原物种种子萌发的直接影响。


种子萌发在调节氮（N）富集下草原群落植物物种组成中发挥着重要作用。全球范围内，陆地生态系统中植物群落结构因氮沉积增强而发生变化。尽管有大量关于增强氮沉降对成熟植物群落影响的研究，但很少有研究关注种子萌发。通过实验室实验，我们报告了五种氮浓度（包括 0、5、10、20 和 40 mM N (NH ₄ NO ₃ )）对八种半干旱草原物种种子萌发的影响。结果表明，低氮浓度（5 mM 和 20 mM N）使所有八个物种的平均最终发芽率提高了 4.4% 和 6.4%，但高浓度（40 mM N）则没有影响。较高的氮浓度（20 和 40 mM N）水平使平均发芽率下降 2.1% 和 5.1%，但发芽开始时间呈现相反的趋势，分别在 10、20、20、20 d 延迟了 0.7、0.9 和 1.8 d。和 40 mM N 处理。最终发芽比例、平均发芽率和发芽开始时间在不同物种之间对氮浓度处理的反应存在显着差异。细葱和灰藜的最终发芽率因氮浓度的增加而受到抑制，而委陵菜、车前子和狗尾草的最终发芽率则有所增加。我们的研究结果为半干旱草原群落中基于种子萌发因素的氮沉降引起的物种损失提供了新的见解。