© iForest -Biogeosciences and Forestry IntroductionHigh-temperature heat treatment is considered a suitable method to improve wood characteristics. It reduces toxic chemical applications normally required to increase wood durability (Kandem et al. 2002, Welzbacher & Rapper 2007, Mohareb et al. 2010 and enhance dimensional stability, reducing the hygroscopic behavior of the material (Kortelainen et al. 2006). High-temperature treatment can be viewed as a type of wood modification, due to the possibility of controlling color changes (Bekhta & Niemz 2003, Johanson & Moren 2006, Esteves et al. 2007a, 2008 and mechanical performance (Bekhta & Niemz 2003, Welzbacher et al. 2007, Bal 2014. The process results in a new material in terms of durability, woodwater relationships and some mechanical properties, which exhibits performance dependent on the specific high-temperature treatment conditions (Militz 2002, 2008, but the wood product does not present any environmental hazards in its disposal (Hillis 2006). The final product typically has the disadvantage of reduced mass and mechanical performance, although some difference in degree of change has been observed between softwoods and hardwoods depending on the treatment method (Kocaefe et al. 2010, Li et al. 2011.Therefore, the overall extent of modification and the final result of the process is quite variable. In this study, we assessed heat treatment effects on Corsican pine and Douglas fir wood properties obtained from a conifer reforestation site in Italy, with particular consideration of different sapwood and heartwood behavior. This timber is considered poor quality and is currently used as biomass for energy or packaging. Materials and methods Study area Forty Douglas fir (Pseudotsuga menziesii)and 40 Corsican Pine (Pinus nigra ssp. laricio) trees were sampled in an artificial mixed stand in Poggio Nibbio near Viterbo, Central Italy (latitude 42° 22′ N, longitude 12° 10′ W). Trees were arranged in rows with a cross-distance of 4 m; the stand was thinned to promote tree regeneration and introduction of indigenous hardwoods. The harvested wood is generally of poor quality due to the fact that the trees have grown quite fast, and not straight, producing large rings that contain a high proportion of earlywood. The sapwood is also quite large, particularly in Corsican pine.From each of the eighty trees sampled, single boards 6 cm thick, 80 cm long, and 7 cm in width were produced and subsequently crosscut to obtain two half-boards of approximately 40 cm in length. From these two half boards, we obtained twin specimens measuring 2 × 2 cm in the transverse radial and tangential directions, and 40 cm longitudinally. The wood samples were largely juvenile, approximately 10 years in cambial age, and evidence of reaction wood was not observed in any samples analyzed. For each of the 2 × 2 × 40 cm sample pairs, one sample was heat treated, and the second sample was left untreated. Subsequently, two blocks measuring 2 × 2 × 3 cm in size were cut from the end of each sample to...