Roots of the forest primeval

WHEN DRIVING UP U.S. 101 in Northern California, I usually stop for a walk on the Redwood Creek Trail north of the small town of Orick. The trail, which runs 8.2 miles upstream through Redwood National Park to the famous Tall Tree, as it is simply known, seems about as close as you can get today to a complete redwood ecosystem. Of course, the highway passes through ancient groves from Mendocino County north, but they are fragmented compared with those that grow along Redwood Creek, where you can stand by the water and see these trees to every horizon.

It ‘s like the throne room of the redwood gods. The trees don’t disappear into the forest understory, as in most groves: Their entire height is visible, and they seem implausibly tall. The spiky bluish top foliage, evolved to resist wind and ultraviolet rays, is very different from the short, dark green needles of the lower branches. Sitka spruce, western hemlock and grand fir also grow at Redwood Creek, unlike in most of the groves to the south where Douglas fir is the only other emergent conifer.

Another outstanding thing about the trail is the wildlife. Big animals are not a regular feature of most redwood groves. But here I often see elk -- sometimes a lot of elk. Black bears are not uncommon. A small one, sitting in a glade near the trail head as I started on a recent walk, was still there when I got back, possibly sleeping. I haven’t seen mountain lions, but many hikers have. In 1994, the park closed the trail for a month because lion sightings were so frequent. (There is a wildlife reporting box at the trail head, so you can check on what’s been seen in the last few days. I found an alleged Bigfoot sighting in it once.)

It’s a beautiful picture. But there’s something wrong with it, as becomes evident at the trail’s first crossing of Redwood Creek. In all the times I’ve crossed there, I’ve never seen a fish, not even a minnow. And it’s not surprising when you look in the water. The creek bottom is a flat, sterile stretch of stones, as though just bulldozed, and in a way that’s what happened -- although no bulldozer has been at that stretch of creek for a long time.

Redwood Creek was the largest relatively intact redwood watershed in the early 1960s when conservationists proposed a 90,000-acre national park there. The proposal gained momentum in 1964 when the National Geographic Society measured Tall Tree at 367.8 feet, the world’s record. But Congress included only a 20,000-acre corridor on the lower creek when it established the park in 1968, and timber companies clear cut most of the rest. Meanwhile, storms washed a mass of material from the clear cuts into the creek. Gravel raised the bed 10 feet in places and covered the pools and riffles where thousands of salmon had spawned. Sediment smothered the estuary where young fish had fed.

The floods threatened the redwoods along the creek too, and in 1978 Congress bought 48,000 more acres, most of it already logged, to stop the watershed from deteriorating further. It was the most expensive park purchase the U.S. had ever made. The park now includes the lower third of the watershed, and there is a 36,000-acre “park protection zone” upstream of that.

The mass of gravel from the 1960s is still in the creek, however, and has been moving slowly downstream. The fish habitat has tried to re-form in its wake, but most of the watershed is still subject to logging, and logged parts of the park keep eroding. When a big storm hits, as in 1997, a fresh load of material washes in and again covers the pools and riffles.

At first, park managers thought they could control erosion by traditional measures such as planting trees, but that didn’t work because of the steep slopes and violent storms. They have had to resort to using heavy equipment to restore logging roads to natural contours and recover buried topsoil. This is expensive, and after a quarter century, about half the park’s logged acreage, including 150 miles of logging roads, still awaits rehabilitation.

What then do fish have to do with the redwood gods? In the long run, maybe a lot. Nobody really knows why redwoods grow so tall, but they get biggest on flood plains, where soil nutrients accumulate. Tall Tree is about 600 years old, young by redwood standards -- which suggests by how fast it has grown, how fertile the flood plain has been.

Salmon bring nutrients from the ocean when they spawn and die in-stream, and some of those nutrients must accumulate in the soil. Fossil salmon, dating back 5 million years, have been found along the West Coast; they may in fact have been evolving with redwoods for the 20 million years that the trees have grown here.

One extinct species is the sabertoothed salmon (Smilodonichthys), so called because it had long, curved fangs which it used for mating display, not hunting. It grew into a giant anyway, by filtering plankton with its gills. Like living chinook and coho, Smilodonichthys probably died in the stream after mating; its fossils occur in river deposits with mastodon bones. Who knows how tall redwoods grew when it lived?

Yet even if salmon-borne nutrients don’t contribute to redwood height, it seems unlikely that the giant trees will thrive on a flood plain continually torn by the erosion that destroys fish habitat. Changing conditions after 1964 have killed Tall Tree’s top. Maybe you can’t have one without the other.