Jeffrey W. Ubben of Martha Stewart Living Omnimedia has stepped down as the company’s chairman. Ubben will remain a director of the company, and as co-founder of ValueAct Capital, will continue to be the company’s second-largest shareholder.

Thomas C. Siekman, who is currently a director, will take over as chairman of the board.

Additionally, Arthur C. Martinez, who was formerly chairman and CEO of Sears Roebuck & Co., has also stepped down from the board, as well has position of lead director. The lead director position will be eliminated.

Charles A. Koppelman has been named to the board. Koppelman, who was proposed by Martha Stewart, is chairman and CEO of CAK Entertainment Co., a music and entertainment firm.