Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Giant sequoias yield longest fire history from tree rings

19.03.2010
A 3,000-year record from 52 of the world's oldest trees shows that California's western Sierra Nevada was droughty and often fiery from 800 to 1300, according to new research.

Scientists reconstructed the 3,000-year history of fire by dating fire scars on ancient giant sequoia trees, Sequoiadendron giganteum, in the Giant Forest of Sequoia National Park. Individual giant sequoias can live more than 3,000 years.

"It's the longest tree-ring fire history in the world, and it's from this amazing place with these amazing trees." said lead author Thomas W. Swetnam of the University of Arizona in Tucson. "This is an epic collection of tree rings."

The new research extends Swetnam's previous tree-ring fire history for giant sequoias another 1,000 years into the past. In addition, he and his colleagues used tree-ring records from other species of trees to reconstruct the region's past climate.

The scientists found the years from 800 to 1300, known as the Medieval Warm Period, had the most frequent fires in the 3,000 years studied. Other research has found that the period from 800 to 1300 was warm and dry.

"What's not so well known about the Medieval Warm Period is how warm it was in the western U.S.," Swetnam said. "This is one line of evidence that it was very fiery on the western slopes of the Sierra Nevada – and there's a very strong relationship between drought and fire."

Droughts are typically both warm and dry, he added.

Knowing how giant sequoia trees responded to a 500-year warm spell in the past is important because scientists predict that climate change will probably subject the trees to such a warm, dry environment again, said Swetnam, a UA professor of dendrochronology and director of UA's Laboratory of Tree-Ring Research.

During the Medieval Warm Period extensive fires burned through parts of the Giant Forest at intervals of about 3 to 10 years, he said. Any individual tree was probably in a fire about every 10 to 15 years.

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 hundred pounds on them."

To develop a separate chronology for past fires, co-authors R. Scott Anderson and Douglas J. Hallett looked for charcoal in sediment cores taken from meadows within the sequoia groves.

"We can compare the charcoal and tree-ring fire records. It confirms that the charcoal is a good indicator of past fires," Swetnam said.

Such charcoal-based fire histories can extend much further into the past than most tree-ring-based fire histories, he said. The charcoal history of fire in the giant sequoia groves extends back more than 8,000 years.

Increasingly, researchers all over the world are using charcoal to reconstruct fire histories, Swetnam said. Many scientists are analyzing the global record of charcoal to study relationships between climate, fire and the resulting addition of carbon dioxide to the atmosphere.

Swetnam's co-authors are Christopher H. Baisan and Ramzi Touchan of the University of Arizona; Anthony C. Caprio of Sequoia and Kings Canyon National Parks in Three Rivers, Calif.; Peter M. Brown of the Rocky Mountain Tree-Ring Research and Colorado State University in Fort Collins; R. Scott Anderson of Northern Arizona University in Flagstaff; and Douglas J. Hallett of the University of Calgary in Alberta, Canada.

The National Park Service, the U.S. Geological Survey, Mountain Home Demonstration State Forest and Calaveras Big Trees State Park provided funding.

Researcher contact:
Thomas W. Swetnam, 520-621-2112, tswetnam@ltrr.arizona.edu
Related Web sites:
Thomas W. Swetnam, http://tree.ltrr.arizona.edu/~tswetnam
University of Arizona's Laboratory of Tree-Ring Research
http://www.ltrr.arizona.edu
Sequoia and Kings Canyon National Park
http://www.nps.gov/seki/index.htm

Mari N. Jensen | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Earth Sciences:

nachricht 'Quartz' crystals at the Earth's core power its magnetic field
23.02.2017 | Tokyo Institute of Technology

nachricht NASA spies Tropical Cyclone 08P's formation
23.02.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>