(1) The department shall assess land as forest lands according to the following basic determinations.

(a) Forest lands are:

(i) contiguous forested land of 15 acres or more, that is at least 120 feet in width in the same ownership and is capable of producing timber that can be harvested in commercial quantity;

(ii) land that is producing timber or land in which the trees have been removed by man through harvest, including clear-cuts, or by natural disaster, including, but not limited to fire;

(iii) land that is not classified as nonforest land. Nonforest land is used for agricultural, nonqualifying agricultural, industrial, commercial, or residential purposes.