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In EGU General Assembly 2024, Vienna, Austria & Online, 14-19 April
Tropical forests are crucial global climate regulators. They store large amounts of carbon in their living biomass and maintain a delicate biosphere-atmosphere relationship. The carbon cycling in the Amazon Basin has been studied due to the changes promoted in its capacity to absorb and emit large amounts of CO2 concentrations globally in soil, water, and the atmosphere. This research seeks to contribute by identifying human disturbance (biomass burning) and its influence on the Net Exchange of CO2 (NEE) over areas of semideciduous forest located in the Amazon basin. We used micrometeorological measurements (in situ) of 50 km NE of Sinop-MT to calibrate the JULES-CATT-BRAMS numerical system. The model calibration allows estimating the potential for CO2 uptake under smoky conditions, i.e., Aerosol Optical Depth (AOD >> 0.10) and non-polluted (AOD < 0.20). Physiological optimums for AOD, f, PARDF, Tair, VPD, and TdF are determined and used as inputs for approaches concerning Carbon pricing in the Amazon basin. Our preliminary results show statistically significant reductions in %NEE for high aerosol loads (AOD > 1.0), relative irradiance f < 0.60, and Solar Zenith Angle (SZA < 70) values. We found a decrease of about 40 % in f and an increase from 0.10 to 5.0 in the AOD values at 500 nm. Likewise, a 25-110 % increase in NEE flux for AOD levels above approximately 1.25 is significantly linked to the rise of 40-60 % in the Fraction of Diffuse PAR radiation (PARDF) due to the impact of Biomass Burning Organic Aerosols (BBOA). We also noted statistically significant reductions and increases in biophysical variables such as leaf canopy temperature (TdF ~ 3 ºC) and relative humidity (URair ~ 20%), both found under extremely smoky sky conditions. These results can help better represent the physical processes currently implanted in the JULES system and, therefore, the photosynthetic responses of semideciduous forests to regional carbon cycling in the Amazon. Furthermore, we expect this information to guide truly sustainable public policies based on economic development from the preserving forest ecosystems and Brazilian biomes. The noteworthy impact on carbon cycling in semi-deciduous forest environments in the Amazon arises from decreases in the Net Ecosystem Exchange (NEE) flux. This reduction, attributed to the excessive rise in BBOA aerosol concentration, leads to a notable decline in the photosynthetic capacity of plants. Additionally, the substantial decrease in solar radiation fluxes (f < 0.20) caused by regional fires further contributes to this effect. Consequently, these findings significantly enhance our understanding of the carbon cycle in the Amazon region and globally.
