The department shall be headed by and under the independent direction, supervision and control of a Commissioner of Corrections, hereinafter referred to as “the commissioner,” who shall be appointed by and serve at the pleasure of the Governor. The Governor is hereby authorized to set the salary of the commissioner at the same level of any cabinet officer or at a reasonable level in excess thereof. The commissioner, without additional compensation, shall also serve as and exercise the authority, functions and duties of the Commissioner of Corrections as that position otherwise exists under the laws of Alabama, it being the intention of this section that there be but one Commissioner of Corrections.