Trends in carbon sink along the Belt and Road in the future under high emission scenario

Abstract

Over the past three decades, the drawdown of atmospheric CO2 in vegetation and soil has fueled net ecosystem production (NEP). Here, a global land-surface model (CABLE) is used to estimate the trend in NEP and its response to atmospheric CO2, climate change, biological nitrogen (N) fixation, and N deposition under future conditions from 2031 to 2100 in the Belt and Road region. The trend of NEP simulated by CABLE decreases from 0.015 Pg carbon (C) yr−2 under present conditions (1936–2005) to −0.023 Pg C yr−2 under future conditions. In contrast, the trend in NEP of the CMIP6 ensemble changes from 0.014 Pg C yr−2 under present conditions to −0.009 Pg C yr−2 under future conditions. This suggests that the trend in the C sink for the Belt and Road region will likely decline in the future. The significant difference in the NEP trend between present and future conditions is mainly caused by the difference in the impact of climate change on NEP. Considering the responses of soil respiration (RH) or net primary production (NPP) to surface air temperature, the trend in surface air temperature changes from0.01°C yr−1 under present conditions to 0.05°C yr−1 under future conditions. CABLE simulates a greater response of RH to surface temperature than that of NPP under future conditions, which causes a decreasing trend in NEP. In addition, the greater decreasing trend in NEP under future conditions indicates that the C–climate–N interaction at the regional scale should be considered. It is important to estimate the direction and magnitude of C sinks under the C neutrality target.摘要目前, 在区域尺度, NEP趋势变化的强度和影响机制还存在很大的不确定性. 针对这一问题, 我们选取了一带一路覆盖的区域为研究对象, 基于全球陆面模式 (CABLE)和第六次国际耦合模式比较计划 (CMIP6), 评估了历史和未来NEP趋势的变化, 分析了影响的机制. 从过去到未来, CABLE结果表明NEP的趋势从 0.015 Pg C yr−2 减少到 –0.023 Pg C yr−2; CMIP6结果为从0.014 Pg C yr−2转变为–0.009 Pg C yr−2. 气候变化是引起这一变化的主因. 我们的研究结果强调了碳-气候-氮相互作用的重要性, 这对碳中和目标下碳汇潜力的准确估算尤为重要.