Source: https://www.cbnbl.org/system/files/2018-03/Guide%20des%20v%C3%A9g%C3%A9tations%20foresti%C3%A8res%20et%20pr%C3%A9foresti%C3%A8res%20de%20la%20r%C3%A9gion%20Nord-Pas-de-Calais_0.pdf