关键词: 森林植被, 固碳, 能源碳排放, 碳抵消, 北京市

Abstract:

Objective: To investigate the carbon sequestration by forest vegetation and its offsetting effect in Beijing, and to predict the carbon offsetting potential in the future up to the carbon neutral year, with a view to providing a scientific basis for carbon sequestration by forest vegetation, energy saving and emission reduction, and carbon neutralization pathway in Beijing. Method: Forest inventory data, photosynthetic rate method and IPCC inventory guidelines were used to study the spatial and temporal dynamics of vegetation carbon fixation, energy CO₂ emissions and intensity from 2000 to 2020, to evaluate the offsetting effect of carbon sequestration by forest vegetation on CO₂ emissions, and to predict the carbon offsetting potential in the future up to the year of carbon neutrality by using the GM(1,1) gray prediction model. The potential of carbon offsetting was predicted by using the gray prediction model of GM(1, 1). The average carbon sequestration capacity of shrubs, deciduous broadleaf forests, evergreen coniferous forests and deciduous coniferous forests in the past 20 years was 4.24, 4.60, 1.68 and 1.95 t·hm^?2a^?1, respectively. Miyun District had the highest growth in vegetation carbon fixation and Xicheng District had the lowest, with cumulative increases of 2.27×10⁵ and 7.86×10² t·a^?1, respectively, from 2000 to 2020.The city’s total energy carbon emissions from 2000 to 2020 showed a trend of first increasing and then decreasing, with a cumulative increase of 1.98×10⁷ t·a^?1 increased by 21.64%; Chaoyang District has the highest CO₂ emissions, and Yanqing District has the lowest, respectively, 1.54×10⁷-2.46×10⁷ and 1.78×10⁶-2.20×10⁶ t·a^?1. Xicheng District has the most significant energy emission reduction, and Changping District has the fastest growth in energy CO₂, emissions; the intensity of Beijing’s carbon emissions per unit of GDP has increased from 2.79 t per ten thousand yuan in 2000 to 0.32 t per ten thousand yuan in 2020, with a clear downward trend; Miyun District has the highest CO₂, emission intensity, and Xicheng District has the lowest, at 0.79-9.76 t per ten thousand yuan and 0.11-2.08 t per ten thousand yuan, respectively.The carbon offsetting effect of Beijing’s forest vegetation from 2000 to 2020 ranges from 1.56% to 2.50%, with shrubs being the highest and deciduous coniferous forests being the lowest. The average value of the offsetting effect of carbon sequestration by Beijing’s forest vegetation on CO₂ energy emissions in different periods of time is 4.3% in each district, and it is the highest in Yanqing District and the lowest in Xicheng District, with 15.91% and 0.02%, respectively. By 2060, the carbon sequestration and carbon offsetting effect of forest vegetation in Beijing will increase to 8.01×10⁶ t·a^?1 and 15.44%, respectively, with an average annual increase of 13.29% and 1.30%, and the CO₂ energy emission will decrease to 4.99×10⁷ t·a^?1 with an average annual decrease of 2.76%. Conclusion: The carbon fixation of forest vegetation in Beijing increases rapidly from 2000 to 2020, and the carbon fixation of different vegetation types is highest for shrubs, followed by deciduous broad-leaved forests, evergreen coniferous forests, and lowest for deciduous coniferous forests; CO₂ energy emissions increase first and then decrease, and the carbon offsetting effect of forest vegetation is on an overall rising trend; in order to enhance the contribution of carbon neutrality of forest vegetation in Beijing. In order to increase the carbon neutral contribution of Beijing’s forest vegetation, it is necessary to optimize the composition of forest species, increase the proportion of broadleaf forests, and improve the quality of forests in the future.

Key words: forest vegetation, carbon sequestration, energy carbon emission, carbon offset, Beijing