The director of the National Park Service announced her resignation Wednesday from an agency often at odds with environmentalists and Westerners for shifting its focus from conservation to recreation.

Fran Mainella headed the agency for six years and most recently oversaw a controversial rewrite of management policies for the parks under its care. Mainella is leaving her position to devote more time to her family, according to a Park Service release.

Interior Secretary Dirk Kempthorne told Mainella that perhaps her most important contribution was her "effort to foster a culture of partnership within the National Park Service," according to a letter released by the Interior Department.

Mainella and the Park Service were sharply criticized by some members of Congress after the agency released a management proposal that would have placed more emphasis on recreation and expanded the use of snowmobiles and ATVs on federal land.

A new draft of the plan released by Kempthorne last month retreated from that initial proposal, winning praise from environmentalists.

Mainella was also criticized for excessive travel among her ranks.

Lawmakers who oversaw the Park Service budget called Mainella to Capitol Hill in March 2004 after records showed she and other agency employees had spent $94 million on travel in the previous two years. In one case, an official took a $9,315 trip to Africa.

Agency officials later said that they had reduced travel costs. They also defended Mainella's domestic travel, saying she has been the first director to ever visit many smaller and lesser-known national parks.

Sen. Ken Salazar, D-Colo., one of several Western senators to have expressed concern about the emphasis the park service put on recreation over conservation, said he had disagreed with Mainella on the direction the agency was going but that he believes much of it was directed by administration officials "at a pay grade higher than Fran Mainella."

When it came to reworking the management plans, he said, "I think Fran was a positive agent in terms of helping us move to a positive conclusion."