Land management of formerly subtropical Atlantic Forest reduces soil carbon stocks and alters microbial community structure and function

Soil carbon (C) sequestration has been proposed as one means to mitigate the effects of climate change and to guarantee food safety. However, forest conversion to managed land uses can deplete soil C stocks and affect soil microbial communities, potentially impacting a wide range of ecosystem services. Our objective was to investigate the effect of forest conversion to intensive land uses on soil C dynamics and soil microbial community structure and function in the subtropical portion of the Atlantic Forest biome. We evaluated four land uses - forest fragment, grassland, and agriculture with five or fifty years of cultivation. We analyzed soil C pools, edaphic variables, and soil bacterial/archaeal (16S) and fungal (ITS) communities. Forest conversion to managed land uses reduced soil C stocks and altered soil microbial community structure, with implications for soil C dynamics. Bacterial/archaeal and fungal community composition were strongly correlated with pH, base saturation, and calcium (Ca) and magnesium (Mg) content. However, soil C pools were not associated with potential extracellular enzyme activity or microbial diversity. Finally, the fungal species Mortierella minutissima ASV_1 and several bacterial groups were positively correlated with soil C stocks, potentially representing indicators of soil C storage. Our study indicates that land use change affects the interplay between soil microbial communities and soil C pools, with consequences to soil C storage. Our findings may support the development of soil C enhancement programs within the Atlantic Forest biome. •The conversion from forest to managed land uses reduced soil carbon (C) stocks.•Potential beta-glucosidase and arylsulfatase activity were not related to soil C.•Land use shapes microbial associations with soil carbon pools in subtropical soils.