Redwood canopy

I continue to work my way through the New Yorker subscription, little read when it first arrived.

Richard Preston, author of The Hot Zone, that scary book about ebola that was the big thing a few years ago, has an article about coastal redwoods in the Feb 14 & 21, 2005 issue. Guided by Steve Sillett, a professor at Humboldt State, Preston takes to the trees, using a gentle-on-the-giants climbing method, soft ropes, no spikes, a lot of dangling hundreds of feet in the air.

Some excerpts:

"As a young redwood reaches maturity, it typically loses its top. The top either breaks off in a storm or dies and falls off. A redwood reacts to the loss by sending out new trunks, which typically appear in the crown, high up in the tree, and point at the sky like fingers of an upraised hand.

...

"The general opinion among biologists ... was that the redwood canopy was a so-called 'redwood desert' that contained not much more than the branches of redwood trees. ... The old-growth redwood forest, Sillett found, is packed with epiphytes, plants that grow on other plants. They commonly occur on trees in tropical rain forests, but nobody really expected to find them in profusion in Northern California. There are hanging gardens of ferns, in masses that Sillett called fern mats. The fern mats can weight tons when they are saturated with rainwater; they are the heaviest masses of epiphytes which have been found in any forest canopy on earth. Layers of earth, called canopy soil, accumulate over the centuries on wide limbs and in the tree's crotches -- in places were trunks spring from trunks -- and support a variety of plant and animal life. In the crown of a giant redwood named Fangorn, Sillett found a layer of canopy soil that is three feet deep.

...

"Sillett and his students have found small, pink earthworms of an unidentified species in the beds of soil in the redwoods. A Humboldt colleague of Sillett's named Michael A. Camann has collected aquatic crustaceans called copepods living in the fern mats. ... Sillett said, 'They commonly dwell in the gravel streams around here.' He can't explain how they got into the redwood canopy. A former graduate student of Sillett's named James C. Spickler has been studying wandering salamanders in the redwood canopy. ... Spickler found that the salamanders were breeding in the redwood canopy, which suggests that they never visit the ground ...

"Old redwood trees are infested with thickets of huckleberry bushes. In the fall, Sillett and his colleagues stop and rest inside huckleberry thickets, hundreds of feet from the ground, and gorge on the berries. He and his students have also taken censuses of other shrubs growing in the redwood canopy: currant bushes, elderberry bushes, and salmonberry bushes ... Sillett once found an eight-foot Sitka spruce growing on the limb of a giant redwood.

...

"Redwoods occasionally shed whole sections of themselves. Sillett calls this process calving. The tree releases a kind of woodberg, and as it collapses it gives off a roar that can be heard for a mile or two, and it leaves the area around the calved redwood looking as if a tank battle had been fought there.

...

"Trees are horrible to one another, and redwoods are viciously aggressive. They drop large piece of dead wood on smaller neighboring trees, which typically shatters the tree. Sillett calls this phenomenon 'redwood bombing.' In this way, a giant redwood suppresses and kills trees growing near it, including hemlocks, spruces, Douglas firs, and big-leaf maple trees. A giant redwood can clear a DMZ around its base, an area covered with redwood debris mixed with twisted and dead trees of other species.

[I'm not sure what the difference is between "calving" and "bombing" ... scale, perhaps?]

...

"At two hundred and ninety feet, I encountered Sillett. He was sitting on a branch inside a spray of huckleberry bushes, and he had a thoughtful look on his face. The main trunk had split open near the branch where he sat, and the opening revealed dead and rotten wood inside the trees. 'This beast is full of rot pockets,' he said. 'These huckleberry bushes are putting their roots through the scars into rotten wood in the center of the tree. One summer, we had half the normal rainfall, but these bushes still put out a full crop of huckleberries. They're getting their water from rotten wood inside the tree.'"

A redwood can be significantly hollowed by fire or, as described above, riddled with rot, but live on and live on. The living part of the tree is just under the bark. Even in an intact tree the core is not really alive.