Coast redwoods (Sequoia sempervirens) normally live between 1,000 and 1,500 years. One redwood was determined to be 2,200 years old. (see “Coast Redwood” on 10-13-18) To achieve these phenomenal life spans, coast redwoods have many adaptations to help them survive.
Redwood trees have tannic acid and terpenoids throughout the plant. These chemicals render the plant resistant to insect attack, fungus and rot. Although some insects, despite the tannic acid and terpenoids, can still attack the trees, they are unable to kill healthy trees.
Coast redwoods have thick, fire-resistant bark with little flammable pitch or resin. If the tree does receive fire damage, it can sprout new branches or an entire new crown. Coast redwood seeds germinate best on mineral soil or other organic seedbeds, but not in its own litter. Thus a fire may also encourage seed germination by destroying the litter. The young seedlings can also grow better after competing species are killed by the fire that stimulated the seeds’ germination.
Coast redwoods can reproduce asexually by sprouting from the root crown, stumps or fallen branches. Adventitious, dormant buds in the bark or in woody swellings (burls) below the soil line are stimulated when the main trunk gets damaged, killed or starts to die. These buds can also spontaneously erupt around the trunk perimeter. When a mature tree is surrounded by these young trees growing from the parent it is called a family ring or a fairy ring.
In flood areas sediments form impermeable barriers that can suffocate existing roots. When the lower trunk and roots are covered by sediment, the existing coast redwood roots grow upward into the newly deposited sediment and a second root system develops. Often the old root system will die.
After a flood or earthquake if the soil becomes unstable and causes the tree to lean, coast redwoods increase wood production on the vulnerable side and create a supporting buttress.
Extremely tall trees have difficulty getting water to the upper leaves because of gravity. Coast redwoods solve this problem through morphological changes in the needles. The upper needles are more awl-like and “succulent” resulting in better water retention. The needles can absorb fog and rain water directly into the leaves from the air, as can the tree bark.
I am always intrigued by the evolutionary adaptations that allow these and all forms of life to thrive.
These coast redwood family rings are growing along the Hiouchi Trail in Jedediah Smith Redwoods State Park, Del Norte County CA.