Soil basal respiration and microbial indicators under different land-use systems in the Mantaro Valley, Peru

Soil respiration is a major carbon flux in terrestrial ecosystems and is highly sensitive to land use and management practices. This study evaluated soil basal respiration (SBR) and its relationship with microbial indicators under different land-use systems in the Mantaro Valley, Peru. Four systems were assessed: forest, pasture, fallow, and cropland. Composite soil samples were collected at a depth of 0-20 cm from three replicated plots per system. Soil basal respiration, microbial biomass carbon (MBC), metabolic quotient (qCO₂), microbial quotient (qMIC), oxidizable carbon (Cox), and permanganate-oxidizable carbon (Coxp) were determined. Forest and pasture systems showed significantly higher levels of labile carbon and biological activity, with Cox values of 28.4 and 14.1 g kg^-1 and Coxp values of 1272.8 and 936.1 mg kg^-1. These systems also exhibited higher SBR (2.85 - 3.36 mg C–CO₂ kg^-1 h^-1) and MBC (214.6 - 251.6 mg kg^-1), indicating favorable conditions for microbial functioning. In contrast, fallow and cropland soils presented reduced labile carbon pools, lower microbial biomass, and decreased respiration rates, reflecting limitations in organic matter inputs. The highest qCO₂ value was observed in the cropland system, indicating lower metabolic efficiency and greater microbial stress, whereas the forest system exhibited the lowest qCO₂, characteristic of more stable ecosystems. Pearson correlation showed that soil basal respiration was strongly related to Coxp and MBC, highlighting the role of labile carbon in microbial activity. Land-use systems significantly affected soil biological quality and carbon dynamics in Andean valley soils.