Abstract: Grassland, as a critical terrestrial carbon reservoir in China, plays a crucial role in climate regulation and achieving the goals of carbon peak and neutrality. Based on relevant literature, we provided a comprehensive overview of representative estimation methods of grassland vegetation carbon storage and analyzed the sources of disparities in different estimation results. The results showed that since the beginning of the 21st century, there has been a significant variation in the estimated carbon storage values of grassland vegetation in China. The estimated carbon storage ranges from 0.56 to 4.66 Pg, with an average of 2.22 Pg. The estimated carbon density ranges from 216 to 1148 g C·m^-2, with an average of 654.23 g C·m^-2. The contribution of litter carbon storage fluctuates between 0.1% and 8.6%, with an average of 5.6%. Neglecting litter would underestimate total carbon storage. The global unit carbon density estimation method showed significant differences with other estimation methods (P<0.05). Carbon concentration in the aboveground, belowground and litter components is approximately 39.3%, 36.6%, and 30.7%, respectively. There were significant differences between the carbon concentration of aboveground vegetation and litter (P<0.05). Using the common carbon conversion factor of 45% could overestimate grassland vegetation carbon storage. Root/shoot ratios varied across different grassland types, ranging from 0.76 to 41.80, with a mean of 9.16. In summary, differences in estimation methods, data sources, and key parameters resulted in variations in the estimates of grassland vegetation carbon storage in China.

Key words: grassland, root/shoot ratio, carbon content, litter, discrepancy