Determining prehistoric understory vegetation of giant sequoia (Sequoiadendron giganteum) stands by soil phytolith analysison
Grassy fuels on the forest floor were not the cause of frequent prehistoric fires in giant sequoia (Sequoiadendron giganteum) groves, according to UC Berkeley researchers and California State Park ecologists.
Fire scars in the rings of giant sequoias describe fire history dating back to the birth of the tree—sometimes as far back as 2,500 years ago. Analysis of tree-ring scars indicates that before settlers came to California low-intensity surface fires, ignited by native people or lightening, burned every five years on average. These small fires cleared only the understory brush and small trees, leaving the larger trees only partially burned and on the whole unharmed. They maintained gaps in the canopy, provided space for developing sequoia saplings, replenished soil, and most likely made hunting and moving around in the forest easier for native people.
Today, park managers are finding it difficult to mimic the frequency and intensity of prehistoric fires. They have developed the practice of introducing similar low-intensity fires into giant sequoia understories, usually in late summer or fall, to remove excess fuels as a guard against the more dangerous, high-intensity fires capable of eliminating entire stands of trees. At best, it takes the forest 15 years to regenerate enough fuel for managers to start another prescribed fire. What has happened to change this interval?
Some believe that gaps in giant sequoia stands allowed enough sunlight to reach the forest floor to support an understory of native grass species, which during the dry season fed frequent surface fires. UC Berkeley’s James Bartolome and his team have found very strong evidence to prove this untrue.
To test the theory, they sampled soil in Calaveras Big Trees State Park in the Sierra Nevada Mountains for phytoliths—rigid microscopic silica bodies found in plants that provide structural stability to leaves and stalks. Thousands of years after a plant dies, its phytoliths remain preserved in the soil, fossilized marks of its existence. Grasses in particular have easily identifiable and diagnostic phytoliths. Soils that were long ago covered with grasses are expected to retain a high concentration of grass phytolyths regardless of historic vegetation changes. The number of grass phytoliths per unit of measurement in Dr. Bartolome’s samples were low enough for him to conclude that the giant sequoia understory was not covered by grasses.
Two possible explanations exist to account for park managers’ lack of success in mimicking prehistoric fires, both of which could be true. First, it is likely that trees in forest stands long ago were more widely spaced. This would cause litter to collect unevenly on the forest floor, leading to very patchy, low-intensity annual fires. Park managers today, however, attempt to burn throughout an entire stand. In addition, park managers do not burn under extreme summer conditions as a safety precaution, but it’s very likely that prehistoric fires ignited during extreme summer heat.
Past logging and fire suppression in Calaveras Big Trees State Park have left an environment in which giant sequoia groves do not regenerate naturally. Tightly crowded thickets of fir and pine trees that have developed in the absence of surface fires put large mature trees at risk of being wiped out by high-intensity crown fires. Park managers expect to use the results of this study to revise their use of prescribed fire as a restoration tool in the giant sequoia forest.
–The researchers’ report has been accepted for publication in the journal Madrono.
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Thinning Would Spur Old-Growth Qualities
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Growing New Giants Through Canopy Gaps
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Fires Were Common in Rainy Northern Forests
For years, Steve Norman had been told that the humid forests of coastal Northern California must be too wet to burn. Scientists who research fire acknowledge its power as a tool for reshaping the landscape, but some areas were considered nearly immune to fire. This assumption meant that the damp forests of Del Norte Coast Redwoods State Park remained a blank file in the coastal forest fire records. Learn more about this research.
Old Redwood Forest Restoration
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Wonder Plot Study Tells Story of Development
In 1923 Emanuel Fritz, then a Professor of Forestry at UC Berkeley, and Woodbridge Metcalf secured for study a one-acre grove of second growth trees along the Big River in Mendocino County. By that year, much of California’s old-growth redwood had been logged and a second generation of trees had begun to grow. Fritz and Metcalf intended to study tree growth on their plot in order to better understand just how a second growth forest develops. Learn more about this research.
Prehistoric Fires Not Caused by Understory Grasses
Grassy fuels on the forest floor were not the cause of frequent prehistoric fires in giant sequoia (Sequoiadendron giganteum) groves, according to UC Berkeley researchers and California State Park ecologists. Learn more about this research.
Thinning Speeds Recovery to Old-Growth
Dr. Christopher Keyes and Andrew Chittick have found that thinning—removing select trees in a second-growth coast redwood forest—speeds up the forest’s development of old-growth characteristics, which include tall and bulky trees, small gaps in the canopy through which sunlight can penetrate, trees of varying heights, thicker tree branches, understory shrubs and ferns, and healthy young saplings. Learn more about this research.
Land Use and Forest Conservation
Dr. Sarah Marvin, professor of Geography at the University of Oregon, has set out to understand how the shape of the land and its use by owners reflect the probability of a privately owned coast redwood forest being protected. The two questions she has asked are: “Are privately owned forests more likely to be protected if they are on bigger parcels?” and “Do traditional, rural land uses as opposed to traditional, residential land uses promote forest preservation?” Answers to these questions might help predict the likelihood of future, private redwood forest protection and—of logged forests—regeneration. Learn more about this research.
Chemicals in Redwood Rings Indicate Past Water Uptake
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Bigger and Older Often Means Better Habitat
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Big Trees: A Bank for Soil Bugs
Legacy trees, old-growth trees left standing in second-growth redwood forests, could serve as a habitat refuge for terrestrial microarthropods, miniscule bugs that live in the forest floor and maintain healthy soils, not to be confused with the bigger arthropods like spiders and bees. Dr. Michael Camann, Karen Lamoncha and Laura Hagenhauer have found substantially more and a wider variety of the soil bugs underneath these so-called legacy trees than beneath surrounding second-growth trees. Learn more about this research.
Bats in Giant Sequoias
Prior to this study, little was known about the bat community in Yosemite’s three giant sequoia groves and virtually nothing was known about how bats use the canopy in any of the Parks’ forests. Dr. Elizabeth Pierson, Dr. William Rainey, and Leslie Chow carried out major research to study bat roosting behavior in fire-scarred hollows at the base of sequoia trees, bat feeding behavior in association with a variety of habitats, and bat activity in the giant sequoia canopy. In addition, they combined observations from this study and others to describe the natural history of Yosemite’s 18 bat species. Learn more about this research.
Redwoods to the Sea Forest Carnivore Tracking Project
From time to time, a resident in Humboldt County will submit a report claiming to have spotted a Pacific fisher or a Humboldt marten. Because Pacific fishers are rare, and because the Humboldt marten was previously thought to be extinct due to human influences such as trapping and logging in their old-growth conifer habitat, these animals remain barely documented. The Corridor from the Redwoods to the Sea, built as a passageway for wild creatures, appears to be prime location to spot small carnivores such as fishers and martens, but despite local accounts, the rare sightings remain unverified by scientists. Where have these small predators gone? Learn more about this research.
Buffer and Let Be
Dr. William Russell found that the negative effects of timber harvesting in riparian coast redwood forests lessen with respect to two conditions; (1) longevity of the forest and (2) wider no-cut buffer zones. Longer-lived forests and forests with wider buffer zones surrounding rivers show less harm from logging. Riparian buffers are strips of forest left on either side of rivers after logging that control the amount of sediment and nutrients filtering into the water. In recently harvested forests and ones with thin or no buffers, young tree crowns crowd the canopies, letting through less sunlight, deciduous hardwoods thrive, extra dead wood litters the forest floors, and exotic and disturbance-prone understory species invade. These alterations, in addition to affecting the physical structure of rivers, down the line cause higher levels of organic material to filter into them. Learn more about this research.
Humboldt Martens Need Old Growth
It’s likely that Pacific fisher (Martes pennanti pacifica) populations are well distributed in Northern California’s Redwood National and State Parks (RNSP) for the same reason that Humboldt martens (Martes americana humboldtensis) have disappeared, according to research done by Keith Slauson, William Zielinski, and Gregory Holm. Second-growth forest habitats that cover a majority of the park are fishers’ sweet and martens’ sour. Learn more about this research.
Wandering Salamanders Choose Direct Route to Good Food
Wandering Salamanders (Aneides vagrans), in addition to dwelling on the ground, have been found in high-up patches of humus moss mats in trunk crotches, on limbs, under bark, and in the cracked and rotting wood of coast redwood trees. They may inhabit forest canopies, the researchers of this study speculate, because of a more profitable food resource available there. Learn more about this research.
What limits redwood height?
In the upper reaches of their crowns, coast redwoods struggle to lift water and nutrients into their leaves. This struggle begins a process that limits tree growth, according to a team of researchers studying redwoods in Prairie Creek and Humboldt Redwoods State Parks. Learn more about this research.
Sponge-like Mats Make Good Habitat in Redwood Canopies: Wandering Salamanders Benefit
Based on their research in Pairie Creek Redwoods State Park, Anthony Ambrose and Stephen Sillett have found that mats of humus soil deposited as high up as 265 feet in the crowns of coast redwood trees moderate the climate around them. This makes the mats habitable to a wide variety of insects and animals more commonly found on the forest floor. Learn more about this research.
Giant Sequoia Ecology Cooperative Web Site
Finding scientific resources on a specific plant species like the giant sequoia can be a daunting task. From the tangled network of information on the World Wide Web, the Giant Sequoia Ecology Cooperative Web site provides quick resources, ranging from maps and informational documents to expert contacts, which link the world to data on this rare tree, found only along the western slopes of the Sierra Nevada. Learn more about this research.
Balanced Management of Giant Sequoias
Giant sequoias are sometimes simply referred to as “big trees” and with good reason: They are the largest trees by volume and among the largest living things on Earth. These massive trees do not function in a void; they are supported by an intricate network of natural processes that keep the ecosystem working properly. Learn more about this research.
Epiphytes Provide High-Up Base for Biodiversity
William Ellyson and Stephen Sillett found evidence that demonstrates that epiphytes—plants that use other plants for mechanical support—play a crucial role in maintaining the biodiversity of redwood forest canopies. It’s well known that these hangers-on thrive in the old-growth Douglas-fir forests of Oregon and Washington, in places amassing the weight of two concert grand pianos per acre. Ellyson and Sillett reveal in this study that Douglas-fir has a rival in Sitka spruce, a tree that grows in and among northern coast redwood forests and supports a shockingly high diversity of epiphytes. Learn more about this research.
Bigger Preserves Have Better Chance to Prevail
Dr. William Russell, Dr. Joe McBride, and Ky Carnell have found that old-growth coast redwood forest reserves with areas larger in proportion to the length of their perimeters suffer fewer negative effects from exposed edges. Learn more about this research.
Bibliography Provides Easy Access to Coast Redwood Research
Coast redwoods have captivated scientists since their discovery, and thousands of articles, dissertations, and books have been written in an attempt to decipher various aspects of these magnificent trees. Finding all of this information was considerably more challenging until Deborah Rogers, a research geneticist and conservation biologist with the Genetic Resources Conservation Program at the University of California, Davis, stepped in to organize a bibliography of scientific materials written about coast redwoods in the past 50 years. Learn more.