In this work, the gasification process of five forest species planted in Colombia with potential as energy crops (Acacia mangium, Eucalyptus sp., Pinus sp., Pinus patula, and Gmelina arborea) is studied using a downdraft fixed bed reactor at laboratory scale. The thermochemical process is characterized from the measurements of the process progress velocity, fuel/air ratio, biomass consumption rate, and producer gas energy content. An experimental sensitivity analysis is carried out to establish the effect of the biomass moisture content, bulk density, heating value, and H/C molar ratio in the process. From the results, the better behavior obtained with the pines (Maximinoi and Patula) and the Eucalyptus is highlighted regarding efficiency and producer gas heating value, 30% and 2.9 MJ/Nm3, respectively. The results obtained are attributed to the synergy of the lower moisture content, and the higher apparent density and higher heating value of the pines and eucalyptus.