Recent research done by Steve Sillett of Humboldt State University and his colleagues suggests that the President Tree in the Giant Forest area of Sequoia National Park is the world's second-largest giant sequoia tree. Yet, the National Park Service lists it as the third-largest giant sequoia tree. Why the difference?

Nate Stephenson, research ecologist with the U.S. Geological Survey who has studied giant sequoias for more than 30 years at Sequoia and Kings Canyon National Parks, said the volume of the tree's branches are difficult to measure accurately, so the size rankings are based on the volume of the tree's trunk only.

"By trunk volume, the General Grant Tree is second largest and the President Tree is the third largest. If you include branches, the order switches," Stephenson said. "But, no matter which measure of size you choose, both trees are awe-inspiring!

Previously, the President Tree and many other giant sequoia trees were measured by Wendell D. Flint, as published in his book, "To Find the Biggest Tree" (2002). Because living sequoias add new growth each year but can also suffer losses because of breakage, tree dimensions change constantly.

Sequoia and Kings Canyon National Parks continues to maintain its list of the 30 largest giant sequoias by trunk volume only. On this list, the President Tree is ranked the third-largest giant sequoia, with a note that if branches are included it is the second largest.