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生物量在不同器官间的分配是植物对环境变化响应的一个关键生态生理学过程.然而,在全球尺度上有关不同陆地生态系统植物生物量分配对氮沉降响应的认识还比较欠缺.本文通过整合分析333篇已发表文章的5474个观测值,基于“最优分配假说”和“异速分配假说”,评估了全球尺度上氮添加对植物生物量及其在不同器官间分配的影响.结果 表明:(1)氮添加显著增加了整株植物或不同器官的生物量,降低了根冠比和根质量分数,但对叶质量分数和茎质量分数无显著影响;(2)氮添加对不同器官质量分数的影响受实验条件、植物功能性状、纬度、氮添加率等因子单独或交互作用的调控;(3)氮添加对生物量在不同器官间的异速分配率无显著影响,表明氮添加导致的根冠比和根质量分数减少是在异速分配模式下由整株植物生物量增加而致.虽然氮添加改变了地上和地下部分的质量分数,但不同器官生物量间异速分配模式的稳定性表明“异速分配假说”能更好地描述植物生物量分配对氮添加的响应规律.该研究结果将有助于深入认识氮沉降环境下植物生物量的分配规律,同时表明将生物量分配纳入有关氮沉降对陆地生态系统影响的预测模型中的重要性.“,”Aims Biomass allocation to different organs is a fundamental plant ecophysiological process to better respond to changing environments;yet,it remains poorly understood how patterns of biomass allocation respond to nitrogen (N) additions across terrestrial ecosystems worldwide.Methods We conducted a meta-analysis using 5474 pairwise observations from 333 articles to assess how N addition affected plant biomass and biomass allocation among different organs.We also tested the \'ratio-based optimal partitioning\'vs.the \'isometric allocation\'hypotheses to explain potential N addition effects on biomass allocation.Important Findings We found that (i) N addition significantly increased whole plant biomass and the biomass of different organs,but decreased root:shoot ratio (RS) and root mass fraction (RMF) while no effects of N addition on leaf mass fraction and stem mass fraction at the global scale;(ii) the effects of N addition on ratio-based biomass allocation were mediated by individual or interactive effects of moderator variables such as experimental conditions,plant functional types,latitudes and rates of N addition and (iii) N addition did not affect allometric relationships among different organs,suggesting that decreases in RS and RMF may result from isometric allocation patterns following increases in whole plant biomass.Despite alteration of ratio-based biomass allocation between root and shoot by N addition,the unaffected allometric scaling relationships among different organs (including root vs.shoot) suggest that plant biomass allocation patterns are more appropriately explained by the isometric allocation hypothesis rather than the optimal partitioning hypothesis.Our findings contribute to better understand N-induced effects on allometric relationships of terrestrial plants,and suggest that these ecophysiological responses should be incorporated into models that aim to predict how terrestrial ecosystems may respond to enhanced N deposition under future global change scenarios.