The lawful use of land or buildings existing on the date of establishment of any interim agricultural district and rural district in final form may be continued although the use, including lot size, does not conform to this chapter; provided that no nonconforming building shall be replaced, reconstructed, or enlarged or changed to another nonconforming use and no nonconforming use of land shall be expanded or changed to another nonconforming use. In addition, if any nonconforming use of land or building is discontinued or held in abeyance for a period of one year, the further continuation of such use shall be prohibited.