Soil microbial carbon and activity along with land use and geographic gradients

Changes in microbial biomass carbon (MBC) and microbial respiration in soils under five different land-use systems were evaluated at a regional scale in Santa Catarina State, Southern Brazil, to assess the effects of land-use change and geographical distribution on the microbial and environmental patterns related to soil carbon (C) dynamics. Results showed that, in the West mesoregion, changes in MBC were correlated to the sampling season in forest and pasture systems. In the Plateau mesoregion, however, a land-use effect was observed, with MBC decreasing in no-till and crop-livestock integration systems. Forest and grassland sites presented the highest values of MBC and microbial activity, while grassland sites showed lower values of the metabolic quotient (qCO₂) and higher values of the microbial quotient. The qCO₂ was also lower in winter for all land-use systems. The highest total and particulate organic carbon values were found in forest sites. Chemical–physical characteristics were also observed to be significantly correlated with microbiological variables related to soil microbial C dynamics. In conclusion, land-use intensity, season, and location were found to be the main drivers of changes in microbial C dynamics.