Big trees three or more feet in diameter accounted for nearly halfthe biomass measured at a Yosemite National Park site, yetrepresented only one percent of the trees growing there. This means just a few towering white fir, sugar pine and incensecedars per acre at the Yosemite site are disproportionatelyresponsible for photosynthesis, converting carbon dioxide intoplant tissue and sequestering that carbon in the forest, sometimesfor centuries, according to James Lutz, a University of Washingtonresearch scientist in environmental and forest sciences. He's lead author of a paper on the largest quantitative study yetof the importance of big trees in temperate forests being publishedonline May 2 on PLoS ONE. "In a forest comprised of younger trees that are generally the sameage, if you lose one percent of the trees, you lose one percent ofthe biomass," he said. "In a forest with large trees like the onewe studied, if you lose one percent of the trees, you could losehalf the biomass." In 2009, scientists including Lutz reported that the density oflarge-diameter trees declined nearly 25 percent between the 1930sand 1990s in Yosemite National Park, even though the area was neverlogged. Scientists including co-author Andrew Larson of theUniversity of Montana, also have found notable numbers of largetrees dying in similar areas across the West. Because of this, scientists have been keen to study a plot largeenough to detect forest ecosystem changes involving large trees,including the effects of climate variability and change, possibleculprits in the declines, Lutz said. The new 63-acre study site in the western part of Yosemite NationalPark is one of the largest, fully-mapped plots in the world and thelargest old-growth plot in North America. The tally of what's there, including the counting and tagging of34,500 live trees, was done by citizen scientists, mainlyundergraduate college students, led by Lutz, Larson, Mark Swansonof Washington State University and James Freund of the UW. Included was all above-ground biomass such as live trees, snags,downed woody debris, litter and what's called duff, the decayingplant matter on the ground under trees. Even when big trees die, they continue to dominate biomass indifferent ways. For example, 12 percent of standing snags were theremains of large-diameter trees, but still accounted for 60 percentof the total biomass of snags. Live and dead biomass totaled 280 tons per acre (652 metric tonsper hectare), a figure unmatched by any other forest in theSmithsonian Center for Tropical Forest Science network, a globalnetwork of 42 tropical and temperate forest plots including the onein Yosemite. Trees in the western U.S. with trunks more than three feet acrossare typically at least 200 years old. Many forests that wereheavily harvested in the 19th and 20th centuries, or those that areused as commercial forest lands today, don't generally havelarge-diameter trees, snags or large wood on the ground. One implication of the research is that land managers may want topay more attention to existing big trees, the co-authors said. Lastyear in the Yosemite National Park, for example, managers planningto set fires to clear out overgrown brush and densely packed smalltrees first used data from the study plot to figure out how manylarge trees to protect. "Before the fires were started, crews raked around some of thelarge trees so debris wouldn't just sit and burn at the base of thetree and kill the cambium, the tissue under the bark that sustainstrees," Lutz said. In some younger forests that lack big trees, citizens and landmanagers might want to consider fostering the growth of a fewbig-trunked trees, Lutz said. Another finding from the new work is that forest models basedeither on scaling theory or competition theory, which are usefulfor younger, more uniform forests, fail to capture how and wherelarge trees occur in forests. "These trees started growing in the Little Ice Age," Lutz said."Current models can't fully capture the hundreds of years ofdynamic processes that have shaped them during their lifetimes.". I am an expert from custom-textileprinting.com, while we provides the quality product, such as Ladies Neck Scarves Manufacturer , Microfiber Travel Towel, Microfiber Glasses Cleaning Cloth,and more.
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