"By every measure we looked at, the recent drought was hotter," Breshears said, adding that, if anything, the 1950s drought was drier. To see how the two droughts differed, the researchers compared the four driest consecutive years of the earlier drought, 1953-1956, with those of the recent drought, 2000-2003. Moreover, the NDVI measurements for the site at LANL showed that the plot's greenness dropped at the same time and in a similar way.ĭuring a previous multi-year drought in the 1950s, not as many trees died. The region's 60,000 square miles (about 155,000 square km) of pinyon-juniper woodlands became a lot less green starting in 2002, the team found. The weekly composite images came from data collected by AVHRR (Advanced Very High Resolution Radiometer) sensors on National Oceanic and Atmospheric Administration satellites. Rich and his colleagues at LANL and the University of Kansas analyzed satellite images of the region's pinyon-juniper woodlands for the years 1989 through 2003 using a measure of vegetation greenness known as Normalized Difference Vegetation Index (NDVI). The effect was so dramatic it could be detected by satellite. Forest Service's aerial surveys of the region's pinyon-juniper woodlands in 20 revealed significant tree die-off covering more than 4,600 square miles (12,000 square km). Pinyon pines all over the Southwest were doing the same thing. Breshears said, "I would see the trees go from vibrant green to pale, gasping green to pale brown to dropping all their needles." By the end of 2003, more than 90 percent of the pinyons on the plot were dead. Initially the trees managed, but in 2002 the pinyon pines began to die. When the recent drought hit, the scientists were well-positioned to compare how the vegetation fared before and during the drought. "I could see the plot from my office window," said Breshears, who used to work at LANL. In 1992, the team began tracking tree mortality. Temperature and precipitation data were recorded at a nearby site. Roughly every two weeks, Breshears and his colleagues measured soil moisture on the 100-by-150 meter plot (about three times the size of a football field). So in 1987, researchers established a study site in the pinyon-juniper woodland zone at LANL. Geological Survey, NASA and the National Institutes of Health funded the research.Įcologists want to learn more about long-term changes in ecosystems that occur in response to climatic and other environmental variation. Los Alamos National Laboratory (LANL), the National Science Foundation, the U.S. A complete list of authors and their affiliations is at the end of this release. 10 in the online Early Edition of the Proceedings of the National Academy of Sciences. Rich, research scientist at Los Alamos National Laboratory in New Mexico, and their colleagues will report their findings the week of Oct. Cobb, director of the Merriam-Powell Center for Environmental Research at Northern Arizona University in Flagstaff, Paul M. "It was the drought beetles don't get trees unless the trees are really water-stressed," Breshears said.īreshears, Neil S. Bark beetles delivered the knock-out punch. The drought coupled with particularly high temperatures set the trees up to be susceptible to insect infestations. "Here we've clearly documented a case that shows how big and fast the die-off can be." "Scientists are concerned about how fast vegetation will respond to climate change, but we don't have many examples to test our ideas," Breshears said. The researchers confirmed the massive regional dieback of vegetation through both aerial surveys and analysis of satellite images of those states' pinyon-juniper woodlands. Breshears, a professor of natural resources in The University of Arizona's School of Natural Resources in Tucson and a member of UA's Institute for the Study of Planet Earth.Īt study sites in Arizona, Colorado, New Mexico and Utah, the team found that from 40 to 80 percent of the pinyon trees (Pinus edulis) died between 20. "We documented a massive forest die-off and it's a concern because it's the type of thing we can expect more of with global warming," said research team leader David D. The new finding suggests big, fast changes in ecosystems may result from global climate change. Hotter temperatures coupled with drought are the type of event predicted by global climate change models. The resulting landscape change will affect the ecosystem for decades. The high heat that accompanied the recent drought was the underlying cause of death for millions of pinyon pines throughout the Southwest, according to new research.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |