Greater impacts of reduced than oxidized nitrogen enrichment on plant diversity losses in a temperate grassland

文献类型： 外文期刊

第一作者： Ren, Suxian

作者： Ren, Suxian;Huo, Tianci;Gou, Xiaowei;Sun, Xun;Liang, Junyi;Jing, Xin;Jing, Xin;Liu, Weixing;Gou, Xiaowei;Hou, Ru

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关键词： Nitrogen deposition; Plant diversity; Nitrogen form; Light asymmetry; Acidification; NH4+ toxicity; Metal toxicity

期刊名称：ECOLOGICAL PROCESSES （ 影响因子：3.9； 五年影响因子：5.4 ）

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年卷期： 2025 年 14 卷 1 期

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收录情况： SCI

摘要： Background Increasing atmospheric nitrogen (N) deposition is a major threat to plant diversity globally. Recent observations show that the reduced-to-oxidized (NHx/NOy) ratio of N deposition has been changing spatially and temporally. How and to what extent different N forms (i.e., NHx and NOy) influence grassland plant species loss are still unclear. Methods We employed a field manipulative experiment by using three N forms [i.e., Ca(NO3)2, NH4NO3, and (NH4)2SO4] with six N addition levels (0, 4, 8, 16, 24, 32 g N m-2 year-1) in a temperate grassland and conducted a greenhouse experiment culturing four plant species corresponding different plant functional groups under Ca(NO3)2 or (NH4)2SO4 addition. Results Results from our field experiment showed that the plant species loss rate was greater under NH4+-N than NO3--N enrichment. Plant species loss was driven by light asymmetry under NO3--N enrichment, while it was co-driven by light asymmetry and soil acidification under NH4NO3 enrichment. Under NH4+-N enrichment, light asymmetry, pH decrease, NH4+ toxicity, and metal toxicity jointly affected species loss. The greenhouse experiment provided direct evidence that legumes and forbs are more physiologically susceptible to NH4+-induced toxicity than grasses. Conclusions Our results emphasize that N forms play a vital role in affecting grassland plant diversity. This suggests that regions with higher NHx enrichment may experience more severe plant diversity losses as N deposition continues to increase. Therefore, appropriate measures should be adopted to mitigate species losses.

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