Land use change affects soil methane sink capacity of Brazilian biomes

Soils are the only biological sink for atmospheric CH₄, making microbial methane consumption a highly relevant process. Land-use change toward agriculture can inhibit this process through the application of ammonium-based fertilizers. To test whether this effect plays a role in land-use changes in Brazilian biomes, we incubated natural and cultivated soils from four endangered Brazilian biomes: Caatinga, Cerrado, Pampas, and Atlantic Forest. Considering only soils that exhibited net CH₄ uptake, soils oxidized an average of 11.9 µg C kg⁻¹ soil day⁻¹. Ammonium sulfate amendment reduced CH₄ oxidation by 33% in pristine soils, while soils from agricultural fields exhibited no methane uptake. Except for soils from the Caatinga biome, pristine soils consumed atmospheric CH₄ and exhibited higher numbers of methanotrophic bacteria compared to managed soils. Our results suggest that a typical nitrogen source supplying NH₄⁺ did not exert as pervasive an effect on CH₄ uptake as did land-use change itself, reinforcing the importance of ecosystem conservation for maintaining the CH₄ cycle. Additionally, soil nutrient availability, particularly micronutrients, may play a key role in stimulating or inhibiting soil methanotrophy. In times of accelerated climate change in the tropics and globally, it becomes crucial to rethink agricultural practices, biomass production models, and patterns of land use and fertilizer application to minimize potential increases in greenhouse gas emissions