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On the Trails: Red cedars

Posted: June 15, 2012 - 12:01am
Cedar trees, like this one growing near Ketchikan, can grow quite large if left undisturbed. But they are in decline as a result of logging and harsh winters, to name a few.  Courtesy of Pam Bergeson
Courtesy of Pam Bergeson
Cedar trees, like this one growing near Ketchikan, can grow quite large if left undisturbed. But they are in decline as a result of logging and harsh winters, to name a few.

On a recent, one-day visit to Ketchikan, we made the rounds of a few things downtown, and then—to escape the crowds disgorged from four monster cruise ships — we explored some short local trails. In gardens on the way out of town, we noted a peculiar shrub and some unusual purple flowers — things that will require a little research to identify, because we don’t see them around Juneau and even the gardeners among us did not know them. A mini-coup for me was sighting a red-shafted flicker, a big woodpecker not often seen here at home.

As we strolled through a second-growth forest, admiring the lush growth of ferns, we encountered a huge cedar tree and, shortly thereafter, an even more gigantic one, about ten or eleven feet in diameter. Both were somewhat deformed, apparently damaged in their youth, so perhaps that’s how they managed to escape the loggers.

I’m guessing they were red cedars, which are known to get as much as 14 feet in diameter, although, to tell the truth, I’m not sure how to distinguish red cedars from yellow cedars. Only yellow cedars grow as far north as Juneau, where they occur in small, occasional patches and suffer from “yellow cedar decline” caused by frost damage to the roots in spring, when snow cover is poor. So I’ve seldom encountered red cedars, but I’m going to pretend to know that these giants were reds, because some very interesting research on Haida Gwaii (formerly known as the Queen Charlotte Islands), the long-time home of Haida people, provides me with stories to tell.

Red cedars originated somewhere down in the Pacific Northwest but didn’t spread northward until the Pleistocene glaciers retreated. They are not very frost-tolerant, but as the post-glacial climate warmed, their range expanded. Between 2,000 and 5,000 years ago, they arrived in Haida Gwaii and became quite common there. People had already lived in Haida Gwaii for thousands of years, and when red cedar arrived and thrived, the people made good use of it. Accordingly, the archeological record shows a shift toward large houses built of cedar posts and planks, storage boxes, totem poles, masks, and large dugout canoes, which facilitated trade with mainland people (and raids on them, as well) and allowed expanded use of marine resources. Bark, twigs, and roots were also used.

Red cedar joined spruce and hemlock in the forests of Haida Gwaii and eventually spread to most of the islands in the archipelago. Then, in the late 1800s and early 1900s, Sitka black-tailed deer were introduced, to provide a source of venison. (A native caribou had been living in the bogs and open forests of the northern part of Haida Gwaii, but apparently it had become rare, and the last ones seen were shot in the early 1900s; they were declared extinct soon after. Some researchers state that the local Natives did not know much about them, because people were concentrated along the shores and were focused on marine food resources.)

Since its arrival a few thousand years ago, red cedar in this archipelago had evolved in the absence of any major herbivore. It lost most of the defensive chemicals found in mainland cedars. These compounds deter herbivory, but they are expensive to make, so relatively defenseless cedars on the islands could allocate more resources to growth and reproduction, and thus become predominant in the population. However, the prevalence of poorly defended cedars set up a tasty buffet for any herbivore.

Then came the deer, which reproduced rapidly and well, and eventually spread to most of the islands. Their browsing has devastated the originally dense understory and nearly eliminated the regeneration of red cedars, especially where deer have been well established for some decades. Plants that survived browsing commonly have reduced growth and poor seed production. Now red cedars are most likely to be found on a few small deer-free islands or in inaccessible locations such as rocky outcrops. Some older individuals were big enough to escape the jaws of the first deer; these remain as relics of a former forest.

Destruction of the forest understory has had strong negative effects on songbird abundance, particularly species that use the shrub layer of the forest. Breeding populations of several species of warbler, sparrow and thrush are markedly lower than in unbrowsed forest. At least in some years, reproductive success of the few remaining understory birds is reduced as well. Introduction of red squirrels, which are mighty predators on songbird eggs and chicks, in the 1940s didn’t help, of course. Loss of the understory meant both loss of nest sites and loss of food resources for birds; forest insects were significantly less abundant and berry-producing shrubs became rare.

Loss of berry crops also affected other fruit-eaters, including black bears and humans. Blueberries, huckleberries, salal, salmonberries, currants and other species became much less common. Other plants that were important in the human culture also diminished markedly: devil’s club, riceroot, miner’s lettuce and many others. In addition, humans lost much of the red cedar that had become so important in their culture. Thus, the venison came at a rather high price.

 

• Mary F. Willson is a retired professor of ecology.

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