Natural fires occurred approximately every 5-15 years in sequoia groves. Sequoias thrive in a forest with frequent fire which opens the canopy for this sun-loving tree and clears the ground so there tiny seeds can germinate and grow.

Giant Sequoias Yield Longest Fire History From Tree Rings

California’s western Sierra Nevada had more frequent fires between 800 and 1300 than at any time in the past 3,000 years, according to a new study based upon tree-ring research.

The 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 3,000-year record from 52 sequoia trees show that California’s western Sierra Nevada was droughty and often fiery from 800 to 1300, according to the study led Thomas Swetnam, Director of the University of Arizona Laboratory of Tree Ring Research.

Scientists can crossdate multiple samples (no live trees were sampled) by matching characteristic patterns of signature rings, usually years in which the trees grew little. For example, 1580 was an exceptionally dry year that is reflected as a very small ring in most giant sequoias. Once dated the actual calendar years in which fire scars were formed can be determined and a history of fire reconstructed.

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.

“While its intuitive that climate patterns influence fire regimes, this study’s data provides some of the first looks at how past fire regimes responded in a sequoia grove. Periods of droughts saw more frequent, though smaller fires, as a rule. Wetter periods saw less frequent fire. However, this also gave fuels a chance to accumulate and this led to larger fires.”

Giant Sequoias Yeild Longest Fire History From Tree Rings