Dead on the inside, fireproof on the outside. The mighty Redwood tree.
The forest is rich with life as we all know. But life in the forest is in no way peaceful or static. Much like the animal kingdom plants and trees are in a constant struggle for food, water, air and existence itself. The trees of the forest have some very quietly persistent enemies and some very aggressiv enemies. Molds and fungi take their time destroying trees and there are very few trees that do not eventually succumb to presence of fungi. Fire is the natural enemy and it can devastate a forest with no warning and seemingly little effort. Let us not forget perhaps the most aggressive and persistent foe, insects.
But there is one specie of tree that pushes back and continues to survive despite these epic enemies, the mighty sequoia tree.
This beast is known as the General Sherman. It is considered a "middle aged" sequoia at roughly 2000 years old.
Let's start with a look at how fungi work to kill forests and how redwoods push back. Saprophytic fungi, also known as saprophytes, appear as many different forms such as bread mold, mushrooms and puff balls are the most prevalent fungi in the forest. These fungi do not produce their own food and so must live on dying, decaying or dead plants. Parasitic fungi on the other hand live on living plants. Both forms of fungi are adept at taking out most species in the woods such as oaks and all species of pine. The redwood however remains resistant in the most fascinating way. The redwood tree can rot in the heartwood, which is not living tissue anyway, and still thrive. This rot creats what is called "telescoping" or a "chimney" effect. The tannins in the tree are the key. Tannins exist in other species but not to the extent they do in redwoods. This chemical not only resists fungi in all forms but gives the redwood its unique rich tones. Tannin is also abundant in the cone, where it forms about seven-tenths of the substance known as cone pigment. If a tree falls and breaks, the tannin soon covers the broken ends of the tree, making it appear as if it has been burned or creosoted, and this natural treatment protects the wood from decay.
Next enemy are insects. Redwoods inhabit the same forests as the oaks, pines and hemlocks yet while they succumbe to infestations the redwood does not. The heartwood lumber made from the redwood is also extremely resistant to all forms of bugs and so is used heavily in tropical climates.
Fire! This aspect of the redwood is just fascinating. Fire, as we all know is nature's method of clearing out the forest and allowing new growth to take hold. There are two elements in most trees that act as accelerants, pitch and resin. Redwood trees have neither pitch nor resin and this helps retard burning. The second major aspect is the bark. The bark of the redwood tree has asbestos like qualities in its fire resistance. Combine that with the fact that the bark grows to a density of up to two feet in thickness and you have a nicely insulated tree. There are many cases where the heartwood does burn through the tree but as we discussed with the fungi this is of little consequence as the heartwood is effectively rot and not essential to the life of the tree. There are many instances of redwoods having survived as much as twenty fires and are still standing. Fire resistance in redwoods is really about age. Young sprouts will not survive fire events while the mature trees will.
Life after death. The mighty redwood can survive what mother nature throws at her even death itself. Redwood trees do eventually die but they leave usable lumber in the forest for centuries. In 1925, American Forests and Forest Life reported the following example of the durability of a Redwood which had been down for more than 340 years. Three hemlocks, 235, 250, and 340 years old, respectively, were growing directly over a Redwood, which was 78 inches in diameter. The living hemlocks had evidently started from seed that had lodged on the fallen Redwood trunk, and there sprouted. The roots of the seedlings continued to grow on and around the fallen tree until they gained a foothold in the surrounding soil. The fallen tree was still in a sound condition.
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