Section 2. The governing board may appropriate for expenditure for the uses and purposes for which an endowment fund is established so much of the net appreciation, realized and unrealized, in the fair value of the assets of the endowment fund over the historic dollar value of the fund as is prudent under the standard established by section eight; provided, however, the appropriation of net appreciation for expenditure in any year in an amount greater than seven per cent of the fair market value of the institution’s endowment funds, calculated on the basis of market values determined at least quarterly and averaged over a period of three or more years, shall create a rebuttable presumption of imprudence on the part of the governing board. This section does not limit the authority of the governing board to expend funds as permitted under other law, the terms of the applicable gift instrument, or the charter of the institution.