PORTLAND, Maine — The longtime head of a charitable trust in Maine that has given away $145 million over the past 20 years says he’ll be stepping down from his post at the end of next year.

Owen Wells has headed the Libra Foundation since 1989, when it was founded by the late Elizabeth Noyce, a philanthropist who died in 1996. He told the Portland Press Herald he’ll step down as Libra’s president at the end of 2011 and be replaced by Craig Denekas, the foundation’s vice president.

Over the years, the Libra Foundation has given away tens of millions of dollars to hundreds of organizations and causes across Maine.

Its accomplishments include developing the Pineland Center into a national showcase, providing subsidies to send children to summer camp and helping fund the creation of a winter sports center in Aroostook County.