气溶胶直接辐射效应对全球陆地生态系统碳循环的影响

论文利用通用陆面模式CLM4.0-CN对全球陆地生态系统生物地球化学循环过程进行模拟,分析气溶胶直接辐射效应对全球陆地生态系统碳循环的影响。结果表明：气溶胶直接辐射效应使2007年全球陆地生态系统平均总初级生产力（GPP）、净初级生产力（NPP）、异养呼吸（R_H）、自养呼吸（R_A）以及净生态系统生产力（R_eco）都呈现出增加的态势。具体的变化特征则随着地区不同而表现出极大的差异,在非洲中西部、中国中东部、美国东南部和欧洲中南部地区GPP增加,在南美洲亚马逊地区及东南亚等地区GPP减少。NPP和R_A与GPP的分布基本一致。分析发现,气溶胶直接辐射效应导致陆地生态系统碳循环发生变化有如下两方面原因： 1）散射施肥效应,即植被阴生叶可以吸收的散射辐射（光合有效辐射）增加使其光合速率增加;2）辐射变化导致温度和湿度条件发生变化,从而改变植物生物物理和化学过程速率。

Impacts of Aerosol Direct Radiative Effect on Carbon Cycle in Global Terrestrial Ecosystem

The biogeochemical processes in global terrestrial ecosystem are studied using the Community Land Model (CLM), and the impacts of aerosol radiative effects on the carbon cycle in global terrestrial ecosystem are analyzed. Calculations show that the aerosol direct radiative effects caused the global averages of terrestrial gross primary productivity (GPP), net primary productivity (NPP), heterotrophic respiration (R_H), autotrophic respiration (R_A), and net ecosystem productivity (R_eco) to increase in 2007, with significant spatial variations however. For instance, the GPP increased in the mid-west of Africa, the mid-east of China, the southeastern US and the mid-south of Europe, and decreased in the Amazonia of South America and the southeastern Asia. The NPP and R_A showed similar spatial pattern as GPP did. The average changes of GPP, NPP, NEP, R_A, R_H and R_eco in 2007 were +6.47 g C·m^-2 (+1.13%), +2.23 g C· m^-2 (+0.98%), +0.34 g C·m^-2 (+4.04%), +4.24 gC m^-2 (+1.25%), +1.89 g C·m^-2 (+0.86%), +6.13 g C·m^-2 (+1.13%), respectively. Simulations of canopy photosynthesis found that the photosynthetic carbon sequestration by sunlit and shaded leaves was also impacted by aerosols. The photosynthetic carbon sequestration by shaded leaves exhibited similar trend as GPP did, and its global average increased by 23.93 g C·m^-2. The carbon sequestration by sunlit leaves decreased by a global average of -17.47 g C·m^-2. Examinations of the carbon fluxes show that the aerosol direct radiative effects influence the carbon cycle in terrestrial ecosystem via the following two ways: first, the diffuse fertilization effect, i.e. more diffuse radiation being absorbed by shaded leaves of vegetation (photosynthetic active radiation, PAR) results in higher photosynthetic rates; second, the radiation changes lead to changes in temperature and humidity, thereby changing the rates of the plant biophysical and chemical processes.