The objective of this study was to evaluate the impact of burning native pastures and of cultivating Pinus sp in monoculture in Lages, State of Santa Catarina, Brazil. Total organic carbon (TOC), microbial biomass carbon (MBC), microbial basal respiration (C-CO2), the microbial metabolic quotient (qCO2), and the ratio MBC/TOC were analyzed. Four representative areas of the region with 0.5 ha each were selected: (a) native pasture without burning for at least 50 years (NP); (b) native pasture burnt off every year (NPF); (c) natural forest (NF) with predominance of Araucaria angustifolia and (d) eight-year-old Pinus taeda monoculture (PINUS). Data were obtained from six replicate samples composed of nine sub-samples each, from a depth of 0-5 cm, in the four studied areas. The fumigation-extraction method was used for the evaluation of MBC. C-CO2 evolution was obtained under laboratory conditions. The highest C-CO2 values were detected in NF and PINUS, followed by NPF and NP, respectively. The highest values of MBC, TOC and MBC:TOC were detected in NF, but the other areas did not present significant differences among each other. The qCO2 rate was higher in PINUS followed by NPF in comparison with NF and NP. Multivariate analysis was an important auxiliary tool for suggesting MBC as an attribute to discriminate the studied areas.
soil quality bioindicator; total organic carbon; soil microbial biomass carbon; metabolic quotient