Abstract: Clarifying the carbon sink of cropland ecosystem not only plays a significant role in the realization of the carbon neutralization plan for Henan Province, but also provides the helps for low-carbon and sustainable agriculture development. However, current studies on the carbon sink accounting are mainly based on only one single calculation method, lacking of multiple methods comparison. Based on the data of the Third National Land Survey, Statistical Yearbook of Henan Province, and the parameter data in the assessment report of the United Nations Intergovernmental Panel on Climate Change, the net carbon sink method and the carbon sequestration rate method were used to assess the carbon sink of cropland ecosystem in Henan Province. The net carbon sink method estimated the net carbon sink from the perspective of carbon absorption and carbon emission, while the carbon sequestration rate method mainly considered the net carbon sink of cropland soil. The results show that the net carbon sink method is more suitable for calculating the carbon sink of cropland ecosystem in Henan Province, and its value was 3.54 million t C; Meanwhile, the calculation results of the two methods all show that the cropland ecosystem in Henan Province is a carbon sink. Spatially, the distribution of carbon sinks estimated by the two methods presented a generally consistent law, that is, it gradually increased from the northwest to the southeast. On the whole, the carbon sinks of cropland ecosystem in Henan Province estimated in this study are far lower than the results of the previous studies, but it is more reasonable compared with the corresponding carbon sink of the proportion of Henan Province to the national cropland area.

Key words: cropland, ecosystem, carbon sink, net carbon sink, carbon sequestration rate