© SGEM2019 All Rights Reserved. In a laboratory model experiment, the effect of native pyrochars and modified pyrochars, from which labile organic matter were extracted, on substrate-induced respiration (SIR) was evaluated. Native samples of pyrochars were obtained from the remnants of linden wood at low-temperature (250°C), medium-temperature (450°C) and high-temperature (650°C) pyrolysis. Modified pyrochar samples were obtained by extracting labile fractions with cold water, boiling in hot water and treating with an alkaline solution of Na4P2O7-NaOH. The SIR on the 30th and 60th day of incubation of model mixtures was determined. The results showed that after the addition of native pyrochars, there is a short-term increase in the intensity of respiration with a further tendency to decrease. The removal of labile fractions leads to an increase of SIR and duration of CO2 emission due to the priming effect associated with an increase in the availability of pores of pyrochar for soil organic matter and microorganisms.