Li Binbin1, Xu Mingxiang1,2, Li Panpan1

　　1College of Forestry, Northwest A&F University

　　2Institute of Soil and Water Conservation,

　　Chinese Academy of Sciences and Ministry of Water Resources

　　In the past 200 years, CO2, CH4 and N2O in the atmosphere increased by 30%, 145% and 15%, respectively, because of the overuse of fossil fuel, land use change and the intensity of agricultural production. These can further intensify global warming, sea level rise, and also contribute to the natural disasters, for example, forest fire, debris flow and earthquake, etc. As is known to us, there are three large carbon reservoirs, ocean, atmosphere, and terrestrial ecosystem, and the interactions among which maintain the balance of carbon on earth. The most important carbon pool, soil, located at the intersection of atmosphere, hydrosphere, lithosphere and biosphere, is critical for global change and agricultural production.

　　At present, there are lots of reviews about SOC (soil organic carbon), and their publication promotes its development greatly. However, it seems that the traditional ways used to review literatures, for instance, reading literatures, then summarizing and discussing qualitatively, have limitations in the face of tens of thousands of research papers. Many important issues, like the SOC development track and its rule, research hotspots and trends, may be solved by more scientific methods.

　　Based on the WOS (Web of Science) database, bibliometrics was used to quantitatively analyze the historical advances of SOC research since 1992. By taking the advantage of the tool, Citespace V, software for visualizing patterns and trends in scientific literature, we analyzed 21663 research articles focused on this field and documented 锚点keyword co-appearance networks at different time periods. The characteristics of cooperation among main countries, number of publications per year, literature co-citation and keyword co-appearance networks were analyzed here. According to the results above at different time periods, global SOC research can be divided into several stages with their own distinctive features. Besides that, we detect the keywords with a burstiness，which means citations of literature or keywords increasing greatly in a certain period, to identify the research trends in the future.

　　It is not only an attempt to theory discussion, but also the need of practice. We hope that our work can provide guidance for SOC research. Moreover, the visualization of research literature enables us to observe and understand the whole state of the field more intuitively and explore the hidden rules and patterns in the data, which can be a useful supplementary method to traditional literature reviews.