When people say "redwoods," they can mean one of three things. Most likely they are talking about coast redwoods, Sequoia sempervirens, which is the species that grows on campus. However, the term "redwoods" may also encompass giant sequoias, Sequoiadendron giganteum. These are currently the most massive (but not the tallest) species on earth and are coast redwoods' closest relatives. They grow exclusively in select areas of the Sierra Nevadas in California. Lastly, "redwoods" could refer to dawn redwoods, the only other species in the ancient Sequoioideae subfamily. Dawn redwoods were once thought to be extinct but have been discovered surviving in a remote valley in China.
The reason I am so fascinated with coast redwoods is not just that they are the tallest tree in the world. It's not even that they were possibly the most massive species in the world before the biggest ones were felled for logging1.
Until the late '80s and early '90s, scientists assumed that the redwoods canopy, which lay hundreds of feet above their heads and had never been accessed by humans, was pretty much bare of anything except redwood needles. But some pioneering work and innovative exploration by some daring scientists led to the discovery that the opposite is true. In fact, once you start learning about what the top of the redwood forest looks like, the trees seem less like individual plants and more like columns holding up a vast sky world.
Where to start? In the top half of a giant, 300 plus-foot redwood tree (the tallest known is currently 379.1 feet), a whole forest in its own right can emerge from the tree. Extra trunks of the main tree grow along massive limbs, while separate trees such as firs and spruces sprout from the redwood limbs as well. Gardens of ferns, huckleberry bushes, mosses, fungi, and lichens color the canopy and give it the appearance of a hanging jungle. These all grow from soil mats, layers of rich soil built up from years of accumulating redwood needles and other plants. Wandering salamanders are the predators of the canopy, and birds, squirrels, and the occasional raccoon share the space. The diverse plants also sometimes tap their roots into springs, yes, springs in the canopy in areas where wood has rotted around a vein that pulls up water from the redwood's roots. Caves hollowed out from fire add protection for the tree's inhabitants. The redwood canopy can grow so complex that, for example, when canopy researcher Steve Sillett brought his fellow scientist (and, later, wife) Marie Antoine into the canopy for the first time, Antoine became lost in the canopy and it was twenty minutes before Sillett found her1.
In short, redwoods support a shockingly diverse array of species. The tragedy is that during the logging frenzy of the past couple centuries, more than 95 percent of them were cut down. Who knows what unique species depended on some of the 95 percent that are no longer here? Who knows how complex, structurally and biologically, the canopy became? It will take thousands of years of re-growth the get an inkling.
In the meantime, we can watch in our own backyard what happens at the genesis of a forest of giants.
1. Preston, Richard. The Wild Trees: A Story of Passion and Daring. New York: Random House, 2007. Print.
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