Abstract: In order to explore the effects of different nitrogen addition states on grassland biomass， soil organic carbon （SOC）， and microbial biomass carbon （MBC）， a meta-analysis method was used to select 65 documents and 416 sets of data， and the effects of nitrogen addition conditions （Duration of N addition， Rate of N addition and Duration of N addition）， grassland types （Alpine grassland/meadow， desert grassland， typical grassland/meadow， meadow grassland）， and climate factors （mean annual temperature （MAT）， mean annual precipitation （MAP）） on the aboveground and belowground biomass， SOC and MBC of grassland ecosystems were investigated through subgroup analysis. The results showed that nitrogen application significantly affected grassland biomass and SOC； both urea and NH₄NO₃ nitrogen application significantly increased aboveground and underground biomass and SOC content （P<0.05）； the duration of N addition was more than 5 years， and the biomass， SOC and MBC contents increased. In grasslands with MAT>0℃， aboveground and underground biomass and SOC content increased after nitrogen application. Therefore， when conducting nitrogen addition in grassland ecosystems， the effects of both biotic and abiotic factors on soil organic carbon should be considered. The research findings have important implications for the scientific formulation of grassland conservation and management strategies.

Key words: Nitrogen addition, Soil organic carbon, Grassland ecosystem, Biomass, Mean annual temperature, Mean annual precipitation

摘要： 为了探究不同氮添加状态下氮添加对草地生态系统生物量、土壤有机碳（Soil organic carbon，SOC）、微生物生物量碳（Microbial biomass carbon，MBC）的影响，采用Meta分析方法，选取65篇文献、416组数据，通过亚组分析探讨氮添加状态（氮素处理持续时间、年施氮量和施氮类型）、草地类型[高寒草原（草甸）、荒漠草原、典型草原（草甸）、草甸草原]和气候因子[年均温（MAT）、年降雨量（MAP）]对草地地上、地下生物量、SOC以及MBC的影响。结果表明，施氮显著影响草地生物量、SOC；尿素、NH₄NO₃两种施氮类型均可显著增加地上、地下生物量、SOC含量（P<0.05）；氮素处理持续时间5年以上，生物量、SOC、MBC含量均增加。在MAT>0℃的草地中，施氮后地上、地下生物量、SOC含量增加。因此，在草地生态系统进行氮添加时，应考虑生物和非生物因素对土壤有机碳的影响。研究结论为科学制定草原保护与管理策略具有重要的指导意义。

关键词: 氮添加, 土壤有机碳, 草地生态系统, 生物量, 年均温, 年均降水量