Giant Sequoias and fire

05.04.2022

History of fires

Fire is an essential part of life for these trees as the seasons change. From the tree rings that were over 2,000 years old, scientists have been able to determine the frequency of fires that have occurred throughout history. Ground fires occurred regularly, every 6-35 years. This regular alternation of weak fires was mainly influenced by wet and warm seasons. The driest period with the most frequent occurrence of forest fires dates from 800-1300 AD.

The inevitable fire

At first glance, a ground fire might seem harmful to the forest rather than helpful. However, the opposite is true. The fires in redwood groves have removed an excessive layer of dead material that, if accumulated more, could cause a massive fire. The burned build-up of needles and material exposed the ground, while the fire also removed surrounding plant competition. Sequoia trees, due to their thick, heavily flammable bark (sometimes up to 0.6m), can survive and take the chance to reproduce. The cones of this tree open and drop seeds when the warm air from the fire hits the exposed soil. Without these events, germination and growth of new generations would be at a minimum.

THE ARRIVAL OF EUROPEANS

The new paradigm

Native Americans understood the meaning of fire and its importance to the ecosystem. They started these small fires themselves and thus helped the reproduction of large trees. The arrival of Europeans changed everything. Groves of redwoods were gradually occupied by flocks of sheep along with their masters. The new inhabitants perceived a fire in the forest as a threat to their interests and a threat to their way of life. Their effort was to suppress any fire. Since the 1860s, a decline in natural or artificial fires can be recorded. This has caused the reproduction of redwoods to drop to extremely low numbers. From later studies, it was found that redwoods dated from 500 BC to the mid-19th century experienced steady population growth. In the 1920s there was a massive failure in the reproduction of these trees.

Return of the Fire

The collapsing reproduction of new generations and the high accumulation of combustible materials (needles, dry branches...) created a threat to the further functioning of the ecosystem and constituted a potential basis for a massive destructive fire. In 1967, there was a turnaround in the management of redwood parks, where the concept of artificial fires returned after almost 100 years. Sequoia and Kings Canyon were the first national parks in the United States to implement a fire management program, i.e., natural ignition and prescribed burning. In concert with the presence of firefighters and experts, periodic controlled fires are conducted to aid the reproduction of
G. Sequoia.

Video about prescribed fires

Sources:

https://www.nps.gov/seki/learn/nature/giant-sequoias-and-fire.htm

https://www.researchgate.net/publication/260082993_Evolution_of_the_natural_fire_management_program_at_Sequoia_and_Kings_Canyon_National_Parks