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Arbuscular mycorrhizal fungi (AMF) play an indispensable role in terrestrial ecosystem soil organic carbon (SOC) dynamics. Over the past 22 years, numerous researchers have studied the role of AMF on soil the carbon cycle, thereby producing a wealth of knowledge. However, a comprehensive summary and analysis of the basic characteristics, research outputs, and knowledge base is still lacking. To explore the authors, countries, institutions, and keywords involved in the study of AMF effects on the soil carbon cycle, publications between 2001 and 2022 were identified and extracted from the Web of Science Core Collection databases using specific keywords, and a bibliometric analysis conducted on this data using CiteSpace. The number of publications has gradually increased over time, with a notable acceleration from 2017 onward. Most of the authors did not cooperate on a regular basis, and a stable cooperative group had not yet been formed among the core authors. The Chinese Academy of Sciences produced the largest number of publications among research institutions. Specifically, China published the largest number of articles in terms of national contributions, but had less influence in collaborative networks. The most desirable research topics mainly included nitrogen and phosphorus nutrients, root colonization, diversity, organic matter and organic carbon, plant growth, and microbial community. In more recent years, research seemed to focus more on AMF-mediated carbon, nitrogen, phosphorus, nutrient exchange, alterations in microbial community structure, advancements in research techniques and methods, and in-depth studies into related mechanisms. This study serves as a valuable reference for future researchers interested in the effects of AMF on the soil carbon cycle, and provides guidelines for future innovative research.

Increase in nitrogen (N) deposition will cause changes of root morphological and functional traits, thus deeply affecting ecosystem carbon (C) and N cycles. However, the influence of N deposition to root traits under different climatic conditions, and with different N deposition rate and durations were still unclear. Here, a meta-analysis was conducted to evaluate the effects of simulated increase in N deposition on 11 root traits under different conditions. In general, N addition significantly increased root/shoot ratio, fine root diameter, total root biomass, fine root production, fine root turnover rate, root respiration, fine root N concentration, while decreased fine root C/N at the global scale. Under N addition, the increased extents of fine root biomass and total root biomass were significantly greater in grassland ecosystems, while the increased extent of fine root turnover was greater in forests. N addition significantly increased fine root production in snow climate zone where forests with ectomycorrhizae. A pattern may be inferred that with increases in mean annual temperature (MAT) and mean annual precipitation (MAP), N addition decreased fine root N concentration and fine root C/N, while increased fine root turnover at the high-MAT and high-MAP areas. In addition, it may be ascertained that fine roots became shorter in the low-rate and short-term N addition experiments, while roots became longer in the high-rate and long-term N addition experiments. Our study indicates that increase in N deposition will cause intricate changes of root traits due to the diversity of climatic conditions and the uncertainty of increase rate and duration of N deposition in future.