The team also compared charcoal deposits in boggy meadows within the groves to the tree-ring fire history. The chronology of charcoal deposits closely matches the tree-ring chronology of fire scars.
The health of the giant sequoia forests seems to require those frequent, low-intensity fires, Swetnam said. He added that as the climate warms, carefully reintroducing low-intensity fires at frequencies similar to those of the Medieval Warm Period may be crucial for the survival of those magnificent forests, such as those in Sequoia and Kings Canyon National Parks.
Since 1860, human activity has greatly reduced the extent of fires. He and his colleagues commend the National Park Service for its recent work reintroducing fire into the giant sequoia groves.
The team's report, "Multi-Millennial Fire History of the Giant Forest, Sequoia National Park, California, USA," was published in the electronic journal Fire Ecology in February. A complete list of authors and funding sources is at the bottom of this release.
To study tree rings, researchers generally take a pencil-sized core from a tree. The oldest rings are those closest to the center of the tree. However, ancient giant sequoias can have trunks that are 30 feet in diameter far too big to be sampled using even the longest coring tools, which are only three feet long.
To gather samples from the Giant Forest trees, the researchers were allowed to collect cross-sections of downed logs and standing dead trees, he said. It turned out to be a gargantuan undertaking that required many people and many field seasons.
"We were sampling with the largest chain saws we could find a chain-saw bar of seven feet," he said. "We were hauling these slabs of wood two meters on a side as far as two kilometers to the road. We were using wheeled litters the emergency rescue equipment for people and put a couple
|Contact: Mari N. Jensen|
University of Arizona