In the event that lands lie within both a regional fire protection service authority and a forest protection assessment area they shall be taxed and assessed as follows:

(1) If the lands are wholly unimproved, they are subject to forest protection assessments but not to authority levies;

(2) If the lands are wholly improved, they are subject to authority levies but not to forest protection assessments; and

(3) If the lands are partly improved and partly unimproved, they are subject both to authority levies and to forest protection assessments. However, upon request, accompanied by appropriate legal descriptions, the county assessor shall segregate any unimproved portions which each consist of twenty or more acres, and thereafter the unimproved portion or portions are subject only to forest protection assessments.