Vacancies on the board of trustees may be filled by appointment by the remaining members of the board of trustees or, if fewer than a majority of the trustees remain on the board, by the board of supervisors for the period until the vacancies are filled by election. An appointment made under this section shall be for the unexpired balance of the term of the preceding trustee. If a board member is absent for four consecutive regular board meetings, without prior excuse, or fails to comply with more stringent attendance requirements for regular board meetings included in the bylaws governing the board, the member’s position shall be declared vacant and filled as set out in this section.