PORTLAND, Ore. (AP) - A federal appeals court panel is deciding a question pivotal to salvage logging: When is a tree dead?

A lawsuit raising the question is pitting environmentalists against the U.S. Forest Service and could decide how the government is allowed to log old-growth conifers burned by fire.

The three-judge panel of the 9th U.S. Circuit Court of Appeals took the case under advisement after a brief hearing in Portland last week.

In 2004 environmental groups accused the Forest Service of violating its own rules that ban the harvest of large, living trees in a burnt area of Oregon's Malheur National Forest. The latest case is over a similar logging plan on the Umatilla National Forest, which is in southeast Washington and northeast Oregon.

After years of often severe wildfires across the West, the Bush administration has aggressively sought to harvest scorched timber before insects or disease make the lumber worthless.

To do that, federal foresters have been using a set of "mortality guidelines" to determine whether a partially burned tree would eventually die, either immediately or from insects or disease.

Critics of the practice say that the agency often tagged healthy trees for harvest and that trees marked for cutting continued to thrive for years.

The dispute has largely focused on the Forest Service's definition of the word "live."

Ralph Bloemers, an attorney representing the Spokane-based Lands Council, said the Forest Service's rules governing old-growth logging say trees larger than 21 inches in diameter have to be dead before they are cut.

But under the mortality guidelines, the agency has been approving logging of trees it predicts are "dying."

Bloemers told the judges the practice used flawed science to justify logging for financial gain, not forest health and said the Forest Service did not hold public hearings on the new guidelines.

But David Shilton, a federal lawyer representing the Forest Service, argued that the guidelines have proved accurate, especially after amendments requiring rigorous standards for testing whether a tree can absorb water after its roots are damaged by fire.

In previous arguments, conservation groups have prevailed.

In 2004, a federal judge in Portland stopping logging of 209 acres on the Malheur National forest.

Judge Garr M. King wrote, "The plain meaning of `live' is still living, in other words, `not dead.' "

But the Forest Service continued to apply the "dead or dying" guidelines in other forests.

The latest round involves salvage logging on the Umatilla, where 51,000 acres burned in 2005. The Lands Council and others sued to stop the logging. A federal judge sided with the Forest Service but was overturned on appeal in February 2007.

In the latest round, Bloemers argued that the Forest Service changed its rules after that decision by redefining what the word "live" means. Shilton said the rule change only clarified "the way the Forest Service has always looked at dying trees."

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