Section 22. Within sixty days after the state commission has established a conservation district it shall appoint a board of no less than five no more than seven district supervisors who shall be individual land occupiers residing on or owning land within the district. Supervisors originally appointed hereunder shall serve for terms of one, two, and three years, respectively. Successors shall serve for terms of three years. Successors for full terms of three years shall be elected or removed for cause by the land occupiers in the district. The state commission shall give public notice of each such election by publication in a newspaper published in the district or having a general circulation therein at least ten days prior thereto. The state commission shall prescribe regulations for the conduct of such elections, which elections shall be conducted by the chairman of the state commission or his designated representative. The person receiving the highest number of votes for any office to be filled at such election shall be declared elected. All supervisors shall serve until the qualification of their respective successors. Vacancies shall be filled by the state commission for the unexpired term. District supervisors shall be paid at a rate established by the director, with the concurrence of the state commission for each day of actual service rendered and their necessary traveling and other expenses, subject to appropriation.