This indicator refers to the intensity of use of forest resources (timber). This indicator relates actual harvest or tree fellings to annual productive capacity of forests. Annual productive capacity is either a calculated value, such as an annual allowable cut, or an estimate of annual growth for existing stock. National averages may conceal important variations among forests. Tree fellings are defined as the average annual standing volume of all trees, living or dead, measured over bark (with no minimum diameter) that are cut during the reference period, including the volume of trees or parts of trees that are not removed from forested land, other wooded land and other felling sites. It includes silvicultural and pre-commercial thinnings and cleanings left in the forest, and natural losses that are not recovered. It is measured in thousands of cubic metres. Gross increase corresponds to the average annual volume of increment of all trees over the reference period of all trees, measured to a minimum diameter breast height (d.b.h) of 0 cm. It includes the increment on trees which have been felled or die during the reference period. It is also measured in thousands of cubic metres.