Bren's latest donation brings to $50 million the contributions to the reserve by the Bren Foundation. The money will be spent to cut 30 new trails, some as long as 17 miles.
"I believe we can create a world-renowned park, restored and managed to standards that inspire others," he said.
Although some are wary of entanglements with business, representatives of conservation groups liked what they saw in the land reserve.

"It's a great concept," said Tom Croom, president of the Sea and Sage chapter of the Audubon Society.
Mike O'Connell, executive director of the Irvine Ranch Land Reserve Trust, noted that the reserve is bigger than 75 percent of the properties in the National Park system, including Bryce Canyon. The reserve was formed in 1897 by James Irvine.
Bren said expansion of the trails through the reserve is his "personal passion."
On Saturday, the trust, the company and other conservation groups will celebrate completion of the Mountains- to-Sea trail by setting up refreshment stations at four places along the trail.
Depending on the time of day and luck, hikers and bicyclists may see bobcats, snakes, bats and a variety of birds.