Redwood Forest Fogdrip
Ancient trees not only water themselves using the fog they rake out of the air at night, but contribute in large part to the water table that supports us all. Some folks have been puzzled about why tree-sitters and conservationists make such a fuss about saving old trees and whole forests that are "just sitting around", or might be more useful as redwood decks. It's not just the trees, it's also the water system that supports all life on earth.
Redwood fog dripdwheeler at teleport.com dwheeler at teleport.com
Thu Dec 3 12:11:27 EST 1998
- The following article appeared in The Oregonian on Dec. 2, 1998, pC11-12, and is posted as a courtesy. Forest giants furnish water to neighbors The dense needles of redwoods are a perfect mechanism for collecting the water from fog. By CAROL KAESUK YOON, New York Times News Service Always an a awe-inspiring sight, the giant redwoods that tower along the California coast are perhaps at their majestic best on foggy days, when these ancients, among the botanical wonders of the world, can be glimpsed through wisps of swirling mist. But now scientists are learning that fog among the redwoods is more than just picturesque. They believe fog may be crucial to the well-being of these rapidly disappearing forests. Scientists have long known that when fog rolls into a redwood, water suspended in the fog begins dripping down the tree's limbs, needles and trunk. But in a study to be published in January in the journal Oecologia, Dr. Todd Dawson, a plant ecologist at Cornell University and the University of California at Berkeley, has shown that this curious mechanism can provide an immense amount of water to the trees -- and to the ground around them. The study overturns a major piece of ecological dogma, that plants steal water rather than contribute it to a habitat. In one foggy night, a single redwood can douse the ground beneath it with the equivalent of a drenching rainstorm, and the drops off redwoods can provide as much as half the water coming into a forest over a year. In fact, Dawson concluded, the redwoods' ability to draw water from fog appears crucial in maintaining the wet climate that they and so many other species, some endangered, thrive in. "Plants aren't passive players out there," Dawson said. "They're active in influencing their own environment. I've never been more wet in my life than when I have been in the redwood forest during a major fog event. You're soaking wet when yoiu're underneath one." Dr. Kathleen Weathers, forest ecologist at the Institute of Ecosystem Studies in Millbrook, N.Y., said, "This is really imoportant, not just for redwoods but for the other plants. If you cut the redwoods down, you take away that structure that can intercept the fog and the water will pass right by." Conservationists working to save these charismatic trees, which can inspire people to extremes of impassioned zeal, have long argued that fog drip is vital not only for plants but the endangered animal species, as well as the people who struggle to maintain water supplies in habitats that can see little or no rain in the summer. Coastal redwoods, or Sequoia sempervirens, are found patchily mostly along the California coast and into Southern Oregon. Working in Northern California, Dawson measured the water dripping off redwoods and off artificial fog collectors in forested and deforested areas. He found that redwoods are extremely efficient producers of fog drip. In deforested areas, which warm up and dry out quickly, it is much more difficult to capture water from fog. Dawson also took advantage of the fact that not all water is created equal. Hydrogen and oxygen, the two components of water, come in different forms, or isotopes. Fog water and rainwater can be distinguished from one another by the varying ratio of isotopes they contain. Studying the isotopes in water in different plants. Dawson found that fog drip was an important source of water to redwoods, as well as many other plants. He said sword ferns were at times entirely dependent on the water coming off redwood trees. Positive feedback loop With redwoods thriving in a wet environment and thriving redwoods making the environment wetter, the interaction forms a positive feedback loop. Dawson said even the handsome structure of a redwood itself may help with this feedback. Redwoods may have evolved their structure of many branches and an array of fine needles over the eons becuase the complex structure so efficiently strips fog. "This is a story that gets repeated in a lot of diferent environments around the world," Dr. Tom Hinckley, forest biologist at the University of Washington, said of the interaction between fog and trees. "Until now these fog phenomena have been largely discounted." For local activists who live in and around redwood forests, scientific confirmation of their theories was good news. "When you clear cut, you don't have any input from the fog," said Els Cooperrider, a redwood conservationsit and local radio talk-show host, who said she has made "fog drip" a household word in Mendocino County. "One of the reasons so many people around here have begun to listen to this phenomenon of fog drip is that they've seen their wells and springs dry up." Paul Carroll, lawyer for Friends of the Old Trees, a conservation group in California, said the group has already used fog drip as an arguing point to stop logging. Twice the group prevented cutting in a redwood forest using the objection that the loss of water from fog drip was not addressed adequately in the logging plans that had been submitted. Difficult battle fought Conservationists are fighting a difficult battle as researchers say only 4 percent of the original redwood forest remains standing today and a single old- growth redwood can contain wood worth hundreds of thousands of dollars. Dawson said it remained an open question whether the fog water he studied replenished streams or ground water. Among those eager for answers are biologists interested in the fate of endangered species like the coho salmon, whose streams run through redwood forests before reaching the sea. "I can see this being hugely important," said Dr. Terry Roelofs, salmon stream ecologist at Humboldt State University in Arcata, Calif., explaining that the time coho spend in shallow, drying streams in the summer can be a crucial bottleneck for these fish. "If fog drip contributes to stream flows, that would be a real plus for these animals," he said. While new to biologists, the idea that fog can be a crucial source of water has in fact been around for some time. In coastal regions of South America and in Namibia, where fog is common but water is not, people built elaborate structures -- which function like a redwood's many branches and needles -- to capture water from rolling banks of fog. Illustration captions: 1) Moisture-laden air from the Arctic warms as it descends over the Pacific coast. 2) As it hits air coming off the Pacific, moisture condenses, creating fog. 3) The fog hangs suspended over the ocean until inland air heated by the afternoon sun rises, causing the cooler air suspended over the ocean to rush in. 4) As the incoming fog makes contact with the redwood branches, which are covered with dense groups of fine needles 1/2 to 3/4 of an inch in length, the moisture accumulates and falls from the branches to the vegetation and soil below. 5) The fog drip reduces temperature and raises relative humidity during summer droughts. A relatively small 100-foot-tall redwood can gather the equivalent of four inches of rain in a single evening. 6) Portions of the fog drip are then absorbed into the tree's internal water system. Columns of water are drawn up the tree's tissues from roots to leaves by dragging water up the sapwood, molecule by molecule. Large redwoods release hundreds of gallons of water vapor daily through their foliage, about twice the average use of water for a household of three. Where does the drip water go? 40% - either evaporates or works its way through the ground to the local water system. 25% - moves by runoff toward the ocean 35% - of water is absorbed by roots, which grow only 10-13 feet deep but spread up to 80 feet wide to absorb the fog drip. Posted as a courtesy by: Daniel B. Wheeler http://www.oregonwhitetruffles.com -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own