The deposition of atmospheric N is expected to increase in the future; however, our understanding of the responses of C:N stoichiometry to N deposition in plants, soil, and microorganisms remains elusive. We aim to explore the general patterns and mechanisms of terrestrial C:N stoichiometry to N addition. We present a global meta-analysis based on 827 paired observations from 183 studies to evaluate the responses of above- and belowground C and N concentrations ([C] and [N]) and C:N ratios across various ecosystems to N addition. Using linear mixed-effects models, we tested the effects of N input rates, experimental duration, ecosystem types and background climates on the responses. N addition increased [C] in plant shoots and soil, [N] in plant tissues and soil, but decreased microbial biomass [C], and C:N ratios in plant tissues, soil, and microbial biomass. These responses were more pronounced with higher N input rates and longer experimental durations. These N addition effects were similar among cropland, forest, and grassland ecosystems and were independent of background climates. Our meta-analysis provided further evidence of the consistent responses of C:N stoichiometry in plants, soil, and microorganisms to N addition. Our results will be useful to modelling the responses of terrestrial C and N cycles to various N deposition scenarios.

中文翻译：

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植物、土壤和微生物中 C:N 化学计量对氮添加的响应

预计未来大气氮的沉积量将增加；然而，我们对 C:N 化学计量对植物、土壤和微生物中 N 沉积的反应的理解仍然难以捉摸。我们的目标是探索陆地 C:N 化学计量与 N 添加的一般模式和机制。我们基于来自 183 项研究的 827 个配对观察结果进行了一项全球荟萃分析，以评估各种生态系统中地上和地下 C 和 N 浓度（[C] 和 [N]）以及 C:N 比对 N 添加的响应。使用线性混合效应模型，我们测试了 N 输入率、实验持续时间、生态系统类型和背景气候对响应的影响。氮添加增加了植物芽和土壤中的 [C]，植物组织和土壤中的 [N]，但降低了微生物生物量 [C]，以及植物组织、土壤、和微生物生物量。这些反应随着更高的 N 输入速率和更长的实验持续时间而更加明显。这些氮添加效应在农田、森林和草地生态系统中是相似的，并且与背景气候无关。我们的荟萃分析进一步证明了植物、土壤和微生物中 C:N 化学计量对 N 添加的一致响应。我们的结果将有助于模拟陆地 C 和 N 循环对各种 N 沉积场景的响应。植物、土壤和微生物中的 N 化学计量与 N 添加量。我们的结果将有助于模拟陆地 C 和 N 循环对各种 N 沉积场景的响应。植物、土壤和微生物中的 N 化学计量与 N 添加量。我们的结果将有助于模拟陆地 C 和 N 循环对各种 N 沉积场景的响应。