Canopy Forests of Coast Redwoods
The redwood forests are among the most magical on the planet. The coast redwood (Sequoia sempervirens) occurs naturally along the pacific coast of North America from Oregon to northern Califoria. These coastal forests are situated among the “fog belt”, where cool precipitation and fog move from the ocean towards the coast at night. The fog supplies the trees with a constant water source, and blocks out some of the evaporative rays of the sun, reducing water lost via transpiration. These coastal redwood forests are often referred to as the Temperate Rainforest.
What makes these trees so special? Well, aside from being one of the tallest organisms on the planet (380ft, or ~115m tall), their crowns acts as fractal forests. The canopies of redwoods were once thought to be ecological deserts, nothing more than redwood leaves and branches. But Marie Antoine, Steve Sillett, and Marwood Harris, old growth botanists, and expert tree climbers took the task of climbing one of these skyscrapers to explore the redwood canopy. And what they found was quite different from an ecological desert, but rather a fractal forest, full of epiphytes, trees, and numerous animals. Redwoods have a unique habit known as reiteration: where horizontal branches hundreds of feet off the ground will sprout vertical branches that act as new trees. Some of these reiterated tree sprouts are taller than the largest trees on the east coast. When leaves fall from the redwood canopy, they build up on the lower branches and ultimately form a “canopy soil” that supports other trees and bushes such as, tanbark oak, douglas fir, elderberry, and huckleberry. These sky forests are surprisingly diverse, supporting not only reiterated redwoods, but other dominant species like firs and oaks. This diversity attracts a litany of rodents, birds (songbirds and raptors), amphibians, and insects.
These trees, thought to be 2500 years old (some possibly as old as 3-5,000 years), operate at a scale different from humans, almost a geologic timescale, where gardens grown in their canopy take 700-1000 years to form. Between 1970 and 1990 about 96% of the redwood forests were cut down in the United States, but the remaining 4% is now under government protection. As an ecologist I would revel in the opportunity to meet and study these special trees while so few remain.
Beautifully described by Richard Preston