Research status and development trends of soil nitrogen cycle in grasslands during 2010 − 2020

Nitrogen is the main component of proteins, nucleic acid, chlorophyll and other substances, and is the main factor limiting ecosystem function. The nitrogen cycle is one of the core element cycles in soil ecosystems and links the grassland ecosystem with society and the larger environment; in particular, nitrogen input is crucial to the level of grassland productivity. A loss in soil nitrogen will reduce environmental quality and affect human life. Therefore, the study of soil nitrogen cycle in grassland is of great significance for maintaining the structure and function of grassland ecosystems and promoting the harmonious symbiosis between humans and nature. Using Citespace software, we analyzed the literature on grassland soil nitrogen cycle during 2010 − 2020 in the core collection database of Web of Science. The results showed that the number of studies of the nitrogen cycle are rising, and in order to improve the quality of the articles, cooperation between domestic and foreign researchers should be further strengthened. Furthermore, we present a systematic review of biological factors (plants, microbes), human activities (grazing, burning, reclamation, mowing, etc.), and abiotic factors (atmospheric nitrogen deposition, warming and CO₂ concentration increase, precipitation) on the soil nitrogen cycle in grasslands. With these factors in mind, we discuss the research problems that need to be studied in the future, and we propose that it is necessary to focus this research on the regional scale under the coupling effect of global change factors. Such an approach could improve the nitrogen cycle model and make possible the sustainable development of grassland areas.