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Forests CHAPTER 6

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Figure 64. Large Snag Habitat. (Kellerman)

Figure 65. Young spotted owls. (Forest Service.)

Figure 64. Large Snag Habitat. (Kellerman)

Logs in streams. Falling trees tumble down the canyons and pile up in great tangled heaps in the streams and rivers that flow through an old growth forest. A typical small stream contains 200-700 tons per acre of woody debris, much greater than that of the neighboring higher ground. [. . .] As on land, trees in streams both create habitat and offer an ample reservoir of food and nutrients. Debris produces habitat by diversifying the flow of the stream and the shape of its channel, thereby generating new gradients in flow rate, water depth, and size of sediment particles, all useful to a wider variety of species. Trees that dam a small stream create ponds and trap fine sediments, while those that partly obstruct it redirect its flow and shape new meanders and smaller pools. [. . .]. During just the last 10 years biologists have gathered increasing evidence that an important group of Northwest animals, the fish of the salmon family, depends heavily on large woody debris in streams. The slower, safer current around logs allows suspended food particles to settle, and the wood itself provides

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concealment from predators. Surveys show that 50% of adults in first order streams spawn in wood-related habitat, and 25% in third order streams. Coho salmon, cutthroat trout, and steelhead take cover in the pools and backwaters around large, stable woody debris, and in coastal Oregon streams, the greater the pool volume, the greater the coho biomass. In several surveys of old growth streams in western Washington before and after clearcutting, in which all large logs in streams were removed, the only salmonid remaining in any abundance was an expanded population of steelhead trout, mostly under a year old. [. . .] Northern spotted owl (Strix occidentalis caurina). Enmeshed in a heated political controversy between timber interests and conservationists, the spotted owl (Figure 65) is an instructive example of just how an animal comes to be dependent on old growth, so dependent that its existence is seriously threatened by routine timber harvest. Before 1970, most information about the owl was sketchy and anecdotal, and conventional wisdom held that it was extremely rare, skittish, and partial to large conifers. Since then, biologists have fitted several hundred owls with radio transmitters and followed their movements over several weeks and months. As a result, we now have solid information about home ranges, habitat use, and age-specific mortality. The preponderance of evidence shows convincingly that the owl is heavily dependent on forests with several

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Welcome new students! This reader is a collection of readings from and about Puget Sound and that will be at the heart of the Bookends orien...