The execution and acceptance of a deed or other instrument described in subdivision (d) of Section 51075 shall constitute a dedication to the public of the open-space character of the lands for the term specified. Any such easement and covenant shall run for a term of not less than 10 years. An open-space easement for a term of years shall provide that on the anniversary date of the acceptance of the open-space easement or on such other annual date as specified by the deed or other instrument described in subdivision (d) of Section 51075, a year shall be added automatically to the initial term unless a notice of nonrenewal is given as provided in Section

51091.