Salt Lake County commissioner Mike Stewart assumed leadership of the commission Monday, replacing Bart Barker who has been chairman of the body for the past three years.

The appointment is Stewart's second term as commission chairman. He filled the post from 1981 through 1985.The commission chairman is appointed for an indefinite term.

Barker is now the chairman pro-tem, the post Stewart formerly held, with the responsibility for conducting commission business when the chairman is absent.

Stewart and commissioner John Hiskey praised Barker's service as chairman, particularly his work on county budget matters. Few commissioners have displayed the keen interest, energy and passion for detail Barker has demonstrated, Stewart said.

The leadership change will not affect the commissioners' portfolio assignments. Barker will continue to oversee the county Administrative Services Department, and Stewart retains the Human Services Department portfolio.

Commissioner-elect M. Tom Shimizu, who takes office next month, will assume the Public Works Department assignment from Hiskey. The commission terms for Barker and Shimizu run through 1990, while Stewart's term of office extends through 1992.