Spatio-temporal evolution characteristics of cultivated land carbon storage and identification of carbon sink areas in Huaihai Economic Zone from 2005 to 2020

Huaihai Economic Zone with a reclamation rate of about 70% is one of the main grain-producing areas in China. It is very necessary to grasp the spatiotemporal variation of the carbon storage for the carbon sink source areas of cultivated land. The driving factors can be used to ensure national food security for agricultural guidance in the achievement of China's "Dual carbon" goals. In this study, the carbon storage of cultivated land soil was calculated using the soil type carbon density of the Huaihai Economic Zone. The net ecosystem productivity (NEP) model was also established to calculate the carbon sequestration of cultivated land vegetation. At the same time, the ArcGIS and Geo-Detector software were selected to study the spatiotemporal evolution characteristics of cultivated land carbon storage, the "carbon" attribute of cultivated land and the driving factors in Huaihai Economic Zone from 2005 to 2020. The results showed that: 1) The soil carbon storage values of cultivated land were 6.028 2×108, 6.055 4×108, 5.927 8×108, and 5.888 9×108 t in the four years from 2005 to 2020, respectively. The land type transfer decreased by 1.393×107 t, indicating a spatial distribution of "high in the east and low in the west". 2) The carbon sequestration of cultivated land vegetation in the four years from 2005 to 2020 was 2.706 7×108, 2.727 0×108, 2.882 3×108, and 2.802 1×108 t, indicating changing trend of "first increasing and then decreasing" with 2015 as the inflection point. The NEP showed a spatial distribution feature of "high in the southeast, low in the northwest". The middle high-value area was extended to the southwest with time. 3) The overall Moran's I of the total carbon storage in the cultivated land were 0.19, 0.19, 0.16, and 0.14 from 2005 to 2020, respectively. There was a downward trend in the spatial distribution and concentration. Specifically, the number of "high-high" type areas also gradually decreased, mainly shifting to the insignificant and "low-high" outlier areas. 4) There were 32 carbon sink areas of cultivated land in the study area, where 21 medium-strength carbon sink areas were mainly distributed in the west, and five high-strength carbon sink areas were concentrated in the northeast. 5) The main factors were traffic accessibility, grain production, NDVI, elevation, slope, and aspect. The secondary factor was population, among the factors driving the spatiotemporal differentiation of cultivated land carbon storage. Therefore, the carbon source counties of cultivated land can take farmland protection and management measures in the carbon sink area, in order to reduce the loss of carbon storage of cultivated land. As such, the quality of cultivated land can be maintained for the carbon sink in the cultivated land ecosystem in the process of farmland protection in the future.