Nematodes are important components of soil food webs and have important ecosystem functions. However, the responses of soil nematode communities to nitrogen (N) deposition have not been well assessed over large spatial scales. Here, we conducted a global-scale meta-analysis of the effects of N-addition regimes (N form, N addition approach, and N addition rate) and environmental factors (ecosystem type, soil depth, climate, and soil property) on the responses of soil nematodes to N addition. The results showed that N addition significantly increased the relative abundance of bacterial-feeding nematodes (23.54%), but decreased the relative abundance of plant-feeding nematodes (−20.24%) and omnivorous-predatory nematodes (−22.28%). Nitrogen addition, however, did not significantly affect total nematode abundance or the relative abundance of fungal-feeding nematodes. Understory N addition usually had larger effects on nematode abundance than canopy N addition. The responses to N addition increased with N addition rate in the case of bacterial-feeding nematode abundance, but decreased with N addition rate in the case of plant-feeding nematode and fungal-feeding nematode abundances. Nematode abundance in grasslands were more responsive to N addition than in forests or croplands, and the responses were affected by soil depth. The response ratios of bacterial-feeding nematodes to N addition decreased with increases in mean annual temperature and mean annual precipitation, while the response ratios of plant-feeding nematodes showed the opposite trend. Soil pH and organic carbon did not affect the response ratios of nematode parameters to N addition except plant parasite index. In summary, the responses of soil nematodes to N addition on a global scale were found to be affected by both N-addition regimes and environmental factors. We suggest that our understanding of how N deposition affects soil nematodes will be increased by additional studies of canopy N addition and of tropical ecosystems.

线虫是土壤食物网的重要组成部分，具有重要的生态系统功能。然而，土壤线虫群落对氮 (N) 沉积的反应尚未在大空间尺度上得到很好的评估。在这里，我们对 N 添加制度（N 形式、N 添加方法和 N 添加率）和环境因素（生态系统类型、土壤深度、气候和土壤性质）对土壤的影响进行了全球范围的荟萃分析。土壤线虫对氮添加的响应。结果表明，N添加显着增加食细菌线虫的相对丰度（23.54%），但降低食草线虫（-20.24%）和杂食性掠食性线虫（-22.28%）的相对丰度。然而，氮添加，对总线虫丰度或以真菌为食的线虫的相对丰度没有显着影响。林下氮添加对线虫丰度的影响通常大于冠层氮添加。在以细菌为食的线虫丰度的情况下，对N添加的响应随着N添加率的增加而增加，但在以植物为食的线虫和以真菌为食的线虫丰度的情况下随着N添加率的增加而降低。草原线虫丰度对氮添加的响应比森林或农田中的更敏感，并且响应受土壤深度的影响。食菌线虫对N添加的响应比随着年平均气温和年平均降水量的增加而降低，而食草线虫的响应比呈相反趋势。除植物寄生虫指数外，土壤 pH 值和有机碳不影响线虫参数对 N 添加的响应比。总之，发现土壤线虫在全球范围内对 N 添加的反应受到 N 添加方式和环境因素的影响。我们建议通过对冠层氮添加和热带生态系统的更多研究，我们将进一步了解氮沉积如何影响土壤线虫。