In Quebec, reforestation by means of coniferous plantation began in the early 1980 and peaked in 1990. However, one wonders if these efforts bore fruits given the high degree of vegetation competition encountered in some plantations. The study objectives were to evaluate and compare changes in forest cover of coniferous plantations established since 1985 on clay soils in the boreal forest. The evaluation was conducted using vegetation indices extracted from images provided by Landsat TM and ETM + for the periods 2000, 2005 and 2010. Digital ortho-photos and field data were used to assess the effectiveness of these indices. The Tasseled Cap Greenness Index proved to be the most efficient to discriminate the type of cover with a Kappa index of 50%. The results show that over 50% of the plantations were classified as mixed (deciduous – softwood) and 25% were classified as deciduous in 2000, while in 2010, 51 % of plantations were mixed and 11 % deciduous. Using a generalized linear mixed model with Laplace approximation, we have established the relationship between changes in cover, age and type of the plantation. The likelihood of an initial deciduous cover to
evolve toward a mixed or coniferous cover was nearly 68 %. The plantation type, its age and cover and their interactions all had significant effects on the probability of a cover to change over time. This project contributed to the assessment of coniferous plantations established between 1980 and 1995 over an area of 18797 ha and confirms that remote sensing tools are effective for tracking large areas while providing quality information for the planning of silvicultural treatments.