On and after December 31, 1955, all growing, standing timber, trees and shrubs in the State of Mississippi, or any county, municipality, levee district, or other taxing district therein, shall be exempt from all ad valorem taxes. And such timber, trees and shrubs after severance shall be exempt from ad valorem taxes so long as such timber, trees, or shrubs shall remain in the log state, or unmanufactured condition and so long as the title thereto shall remain in any person other than the manufacturer or processor thereof.