When the merchantable timber has been sold and actually removed from any state lands, the department may classify the land, and may reserve from any future sale such portions thereof as may be found suitable for reforestation, and in such case, shall enter such reservation in its records. All lands reserved shall not be subject to sale or lease. The commissioner shall certify all such reservations for reforestation so made, to the board. It shall be the duty of the department to protect such lands, and the remaining timber thereon, from fire and to reforest the same.