The nitrogen-15 (¹⁵N) natural abundance composition (δ¹⁵N) in soils or plants is a useful tool to indicate the openness of ecosystem N cycling. This study aimed to evaluate the influence of the experimental warming on soil and plant δ¹⁵N. We applied a global meta-analysis method to synthesize 79 and 76 paired observations of soil and plant δ¹⁵N from 20 published studies, respectively. Results showed that the mean effect sizes of the soil and plant δ¹⁵N under experimental warming were −0.524 (95 % CI (confidence interval): −0.987 to −0.162) and 0.189 (95 % CI: −0.210 to 0.569), respectively. This indicated that soil δ¹⁵N had negative response to warming at the global scale, where warming had no significant effect on plant δ¹⁵N. Experimental warming significantly (p<0.05) decreased soil δ¹⁵N in Alkali and medium-textured soils, in grassland/meadow, under air warming, for a 4–10-year warming period and for an increase of >3 ^∘C in temperature, whereas it significantly (p<0.05) increased soil δ¹⁵N in neutral and fine-textured soils and for an increase of 1.5–3 ^∘C in temperature. Plant δ¹⁵N significantly (p<0.05) increased with increasing temperature in neutral and fine-textured soils and significantly (p<0.05) decreased in alkali soil. Latitude did not affect the warming effects on both soil and plant δ¹⁵N. However, the warming effect on soil δ¹⁵N was positively controlled by the mean annual temperature, which is related to the fact that the higher temperature can strengthen the activity of soil microbes. The effect of warming on plant δ¹⁵N had weaker relationships with environmental variables compared with that on soil δ¹⁵N. This implied that soil δ¹⁵N was more effective than plant δ¹⁵N in indicating the openness of global ecosystem N cycling.

中文翻译：

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土壤 δ15N 是比植物 δ15N 更好的生态系统氮循环指标：一项全球荟萃分析

土壤或植物中的氮 15 ( ¹⁵ N) 自然丰度组成 ( δ ¹⁵ N) 是表明生态系统氮循环开放性的有用工具。本研究旨在评估实验性变暖对土壤和植物δ ¹⁵ N 的影响。我们应用全球荟萃分析方法从 20 项已发表的研究中分别合成了 79 和 76 对土壤和植物δ ¹⁵ N 的成对观察结果。结果表明，在实验升温下土壤和植物δ ¹⁵ N的平均效应大小为- 0.524（95 % CI（置信区间）： - 0.987 至- 0.162）和 0.189（95 % CI：-0.210 到 0.569），分别。这表明土壤δ ¹⁵ N 在全球尺度上对变暖有负响应，其中变暖对植物δ ¹⁵ N没有显着影响。实验变暖显着（p <0.05）降低了碱土和中等质地土壤中的土壤δ ¹⁵ N，在草地/草甸，在空气变暖的情况下，4-10 年的变暖期和温度升高>3  ^∘ C，而它显着 ( p <0.05 ) 增加了中性和细质地土壤中的土壤δ ¹⁵ N并且温度增加 1.5–3  ^∘ C。植物δ¹⁵ Ñ显著（ p <0.05），在中性和精细质地的土壤增加的温度和显著增加（ p <0.05）在碱土降低。纬度对土壤和植物δ ¹⁵ N的增温效应没有影响，但对土壤δ ¹⁵ N的增温效应受年平均气温正控制，这与较高的温度可以加强植物的活动有关。土壤微生物。与土壤δ ¹⁵ N相比，变暖对植物δ ¹⁵ N 的影响与环境变量的关系较弱。这意味着土壤δ¹⁵ N在表明全球生态系统氮循环的开放性方面比植物δ ¹⁵ N更有效。