A giant oak

Wildlands Conservancy naturalists and volunteers survey the champion oak.  (Irfan Khan / Los Angeles Times)

It is impossible to guess how many centuries the tree has stood on the steep, rocky hillside overlooking a narrow stream-fed canyon thick with incense cedars, canyon maples and bracken fern.   (Irfan Khan / Los Angeles Times)

Wildlands Conservancy preserve manager Evan Welsh, left, and volunteer Paul Melzer measure the tree’s circumference.   (Irfan Khan / Los Angeles Times)

“Left alone, oaks are incredibly persistent and able to withstand hardships, lightning, rock falls, floods, wildfires, temperature swings and fungal infections with beauty and grace,” said Rosi Dagit, senior conservation biologist for the Resource Conservation District of the Santa Monica Mountains.   (Irfan Khan / Los Angeles Times)

Wildlands Conservancy naturalists and volunteers hike through a remote canyon to reach North America’s largest oak tree.  (Irfan Khan / Los Angeles Times)

A volunteer Jack Yeaton, left, Wildlands Conservancy director David Myers, preserve manager Evan Welsh, assistant manager Doug Chuddy and conservative director April Sall measure and calculate the height of the tree. The oak’s trunk measured to be 499 inches in circumference and 97 feet high, making it the largest in North America.  (Irfan Khan / Los Angeles Times)