Quantifying the multi-year impacts of Indo-China Peninsula biomass burning on vegetation gross primary productivity in southern China

Biomass burning (BB) emissions in the Indo-China Peninsula (ICP) can be transported to southern China, perturbing the atmospheric environment and climate in southern China. However, the impact of these fire emissions transports on the terrestrial ecosystems in southern China remains unclear. Here we combine several state-of-the-art models and multiple measurement datasets to quantify the impacts of ICP fire-induced aerosol radiation and O₃ damage effect on gross primary productivity (GPP) in southern China during ICP fire seasons (March and April) in 2013-2019. Our results demonstrate that ICP fire-derived aerosols and O₃ collectively reduce annual mean GPP in southern China by 5.4% (13.86 TgC per burning season) under all-sky and 3.4% (12.87 TgC per burning season) under clear-sky conditions. In all-sky, fire aerosols decreased direct photosynthetically active radiation (PAR) by 2.68 W m⁻² while increased diffuse PAR marginally (+0.03 W m⁻²), driving a GPP reduction of 13.36 TgC per burning season across southern China. Concurrently, fire-induced O₃ reduces regional GPP by 0.54 TgC per burning season. In clear-sky, aerosols reduce direct PAR more sharply (−3.22 W m⁻²) but enhance diffuse PAR (+1.51 W m⁻²), resulting the GPP loss to 12.18 TgC, while O₃ damage effect is increased (−0.69 TgC). The fire aerosols contributed to 96.4% of the GPP reduction in all-sky and 94.6% in clear-sky, whereas ozone played a minor role (3.9% in all-sky and 5.4% in clear-sky). This study highlights ICP fire emissions as a significant driver of ecosystem productivity declines in downwind regions, influencing the regional land carbon cycle.