Dynamics of Greenhouse Gas Fluxes in Açaí Cultivation: Comparing Amazonian Upland and Floodplain Soils

Global warming is driven by the increasing atmospheric emissions of greenhouse gases. Soils are highly sensitive to climate change and can shift from being carbon reservoirs to carbon sources under warmer and wetter conditions. This study is the first to simultaneously measure trace gas fluxes in Euterpe oleracea (açaí) plantations in upland areas, contrasting them with floodplain areas managed for açaí production in the eastern Amazon. Flux measurements were conducted during both the rainy and dry seasons using the closed dynamic chamber technique. In upland areas, CO2 fluxes exhibited spatial (plateau vs. lowland) and temporal (hourly, daily, and seasonal) variations. During both the rainy and dry months, CH4 uptake in upland soils was higher in lowland areas compared to the plateau. When comparing the two ecosystems, upland areas emitted more CO2 during the rainy season, while floodplain areas released more CH4 into the atmosphere. Unexpectedly, during the dry season, floodplain soils produced more CO2 and captured more CH4 from the atmosphere compared to upland soils. In upland areas, CO2-equivalent production reached 59.1 Mg CO2-eq ha−1 yr−1, while in floodplain areas, it reached 49.3 Mg CO2-eq ha−1 yr−1. Soil organic matter plays a vital role in preserving water and microorganisms, enhancing ecosystem productivity in uniform açaí plantations and intensifying the transfer of CH4 from the atmosphere to the soil. However, excessive soil moisture can create anoxic conditions, block gas diffusion, reduce soil respiration, and potentially turn the soil from a sink into a source of CH4.