Advancing the comprehensive understanding of soil organic carbon priming effect: definitions, mechanisms, influencing factors, and future perspectives.

The soil carbon (C) priming effect (PE), an important phenomenon in soil C cycle research, has garnered extensive attention in recent years. Soil C PE refers to the stimulation or inhibition of the original soil organic C (SOC) decomposition rate by newly added organic matter in the soil. Its mechanism of action involves the activity of soil microorganisms. Fresh organic matter input provides an additional source of energy and nutrients for soil microorganisms, prompting changes in microbial community structure and activity, which in turn affects SOC decomposition. Easily decomposable organic matter may stimulate rapid microbial growth and metabolic activity of microorganisms, thereby the decomposition accelerating of original SOC and producing a positive PE, whereas recalcitrant organic matter may lead microorganisms to preferentially utilise the newly added C source, thereby inhibiting original SOC decomposition and producing a negative PE. There are numerous factors influencing soil C PE, including organic matter properties such as chemical composition, C:N ratio, and lignin content; soil environmental factors such as temperature, humidity, and pH value; and land-use patterns and vegetation types. Research on soil C PE is crucial for an in-depth understanding of the soil C cycle, the accurate assessment of dynamic changes in the soil C pool, and the development of sustainable soil management strategies. This study introduces the definition, change mechanism, influencing factors, and research methods of soil C PE and elaborates on the status and deficiencies of PE research, which is helpful for predicting soil C responses to global climate change and provides a scientific basis for improving soil fertility and reducing greenhouse gas emissions.