Comparative Study on Carbon Sink Accounting Methods for Farmland Ecosystems in Shaanxi Province

To screen suitable methods for precise assessment of carbon sink in agricultural ecosystems, the author used the net carbon sequestration method and the carbon sequestration rate method to quantitatively calculate the carbon sequestration of agricultural ecosystems in Shaanxi Province in 2020, and studied the differences in carbon sequestration and spatial distribution between the two methods. The results show that: ① The net carbon sink method has a higher accounting value than the carbon sequestration rate method, and the carbon sequestration rate method only accounts for 12.8%-18.2% of the net carbon sink accounting value. ② Both are in a carbon sink state as a whole. In terms of time series, the total carbon sequestration amount of the net carbon sequestration method showed a fluctuating upward trend from 2005 to 2020, while the carbon sequestration rate method showed a trend of first increasing and then decreasing; In terms of spatial distribution, the net carbon sink method shows central＞northern＞southern, while the carbon sequestration rate law shows central＞southern＞northern. ③ At present, the net carbon sequestration method is more suitable for calculating the carbon sink of agricultural ecosystems in Shaanxi Province, with a value of 5.0766 million tC in 2020. However, considering the factors that increase the rate of no till and straw return, the two methods have consistent accounting units and are comparable. In the future, it is extremely important to increase the monitoring of changes in organic carbon in farmland soil, strengthen research on carbon sequestration measures in farmland management, and accurately evaluate carbon sink in farmland soil ecosystems using the carbon sequestration rate method.