During a thinning, also called intermediate felling, an average of 30 per cent of the trees in a forest are removed. The purpose of thinning is to improve the growth and quality of the remaining trees. During the rotation period of a forest, 2 to 3 thinnings are normally carried out. The first thinning is carried out 30 to 40 years after regeneration. If the maintenance of the seedling stand has been timely and careful, the first thinning usually produces enough saleable wood to be profitable.