By SCOTT SONNER, ASSOCIATED PRESS RENO — Political and scientific angst over forest health, wildfire threats and the effect of salvaging dead trees is spurring new debate in the Sierra over a seemingly simple question: When is a tree dead? Stricter federal standards recently adopted for more than 11 million acres of national forests in California require loggers to leave behind many of the biggest green trees and some dead ones to help forests regenerate. But the rules waive some protections when wildfires kill 75% to 80% of the trees in an area. Environmentalists who have blocked a proposed salvage logging operation near Storrie, Calif., accuse the Forest Service of exaggerating the number of trees killed in a 45,000-acre fire there two years ago. They say the standards are rigged to count many living trees as dead. Critics say the agency is wrong to conclude that a tree qualifies as dead if 65% of its crown is scorched. They say many pines and firs survive 80% to 90% scorching, and some independent scientists agree. Forest Service officials admit that estimating the probability a tree will die is an inexact science. But they are confident about the standards used in the Storrie fire area, 80 miles west of Reno near Lake Tahoe. “We believe we have 75% mortality. Some of these trees have green needles, but they are dead,” said Ed Cole, Forest Service supervisor for the Lassen National Forest, where thebulk of the salvage project is planned. Forest Service officials say more important than the condition of the crown is the inner skin, the cambium, which works as a tree’s circulatory system. “You can fry the cambium and not even scorch the canopy and if the cambium is fried, the tree is dead,” Cole said. “It may not happen overnight,” Forest Service regional spokesman Matt Mathes said, “but the tree will die.” Environmentalists accuse the agency of exploiting the exemptions to remove more than dead trees.”It doesn’t say ‘dying.’ It’s trees that are actually killed–not ‘may die,’ not ‘dying,’ but dead,” said Chad Hanson of Grass Valley, Calif., director of the John Muir Project, one of the groups that won an appeal temporarily blocking the salvage project because the effect on the California spotted owl wasn’t fully documented. Scientists say many variables determine whether a burned or damaged tree will die, from crown survival, cambial condition and root regeneration to climate, geography and the species of tree. “It’s a judgment call,” said Bob Wood, an entomologist at UC Berkeley.”Both sides can argue for a long time about what is going to live or die based on various thresholds. I’m sure that many trees with 65% crown scorch die, but many don’t,” he said. The mortality standards at the 2000 Storrie fire were written in November by Sheri Smith, the Forest Service’s supervising entomologist for northeastern California.Smith said she began research 13 years ago out of concern that the agency’s 4-decade-old standards–primarily 50% crown scorching–meant too many live trees were being given up for dead. “I have the same concerns that Mr. Hanson has–I don’t want to see trees cut that aren’t going to die. But what I want to do is provide the best scientific data for basing decisions,” Smith said.”I’m the one who is going to get called into court for the deposition, and I’m going to be the one the judge asks what kind of data we have.” The 65% standard is based on more recent research with pine trees dating to 1994, including some in the Lake Tahoe region, she said. But not everyone agrees. David Peterson, research scientist with the Forest Service Pacific Northwest Research Station in Seattle, said fire-resistant species like Ponderosa pine and Douglas fir “can tolerate 80% to 90% crown scorch and generally will survive if not injured at the base. “All other things being equal, for fire-resistant trees 65% is a little on the low side,” said Peterson, also a professor at the University of Washington.