The paper addresses an experimental study of the flame speed and of spatial temperature distribution at various depths of the bed of pine needles of Siberian boreal forests, a study of the composition of gaseous species and distribution of their concentrations across the bed during fire spread and the study of the impact of the wind velocity on these characteristics. It has been found that, as the wind velocity rises in the range of 0.12 - 0.2 m/s, the burning regime changes dramatically, as well as the temperature and concentration profiles of gaseous species inside the bed. At low wind velocities, flame penetrates the bed, while at high ones it does not. At wind velocities 0.15 m/s and higher, as the wind velocity grows, together with the dramatic growth of the flame velocity the maximum temperature in the flame front in the middle of the bed decreases from 1200 °С to 600 °С , the width of the combustion zone increases, in accordance with the temperature and О2 и CO2 concentration measurements. The flame front in the middle of the bed is biased relative to the flame front on the bed surface The data obtained in the study may be used in developing a ground fire spread model.