chlorine small that sometimes wafts through the redwood forests during the warm days of summer. It's been fairly noticable for about a month now, though it's patchy and doesn't occur everywhere.
Today's hike was on a trail called "The Lonely Trail", up above Woodside. It was just as well that it was lonely: no one could see Dave and me (mostly me) stopping to sniff bushes and trees and rotting logs and dirt. But alas, no definite culprit emerged. It did seem stronger when we were next to tanoak trees, though that is virtually everywhere in these forests.
Tanoak is short for Tanbark-Oak, or Lithocarpus densiflorus. It's not a true oak (genus Quercus) and is more closely related to chestnuts. But it's like oaks in many ways -- the tough, shiny leaves look a bit like larger versions of our local coast live oak (though the distinctive veins make it easy to tell the two apart). The acorns, too, are very similar to those of live oaks.
The smell definitely wasn't coming from the tanoak leaves, but it did seem stronger near the trunks of some of the tanoaks. I'd always assumed "tan" referred to color (since there are white oaks, black oaks, blue oaks and red oaks, none of which are really those colors). But what if it refers to a tree whose bark is particularly high in tannic acid? What does tannic acid smell like, anyway?
This would still leave some mysteries. Tanoaks are all over bay area parks, not just in redwood forests. What is it about the deep, shady redwood forests which bring out this smell, where it's seldom obvious in the tanoaks of the valleys or rolling hills? Some interaction between tanoaks and redwoods, or ferns? Something that only happens in the shade?
I never found a tree that gave me a clear answer -- I merely picked up subtle hints of chlorine odor from the trunks of a few trees. Returning home to the digital world, I learned that the tanoak tree is indeed very high in tannins, and was extensively harvested for tanning hides. The local native Americans also used the acorns for flour, after leaching them to remove the bitter acid. I found no references to odor from tanoak bark or wood, but a few pages mentioned that the flowers, which hang in catkins, have a foul odor. No one goes into specifics on this odor.
I didn't see many flower catkins on today's hike, but they're listed as appearing in June through October. Looks like I have a research project lined up for the next outing.
[ 22:30 Jul 15, 2007 More nature | permalink to this entry | ]