Grasslands, deserts, mountains and fire

August 05, 2000

Grasslands, deserts, mountains and fire: US Geological Survey presents studies at ecological society of America

Birds and small animals in America's grasslands: Can they live together in harmony?

What is causing the high mortality rates of grassland birds in Colorado? A chief cause may be small mammals such as ground squirrels and mice that invade the nests and eat the eggs. Some of the bird species that may be threatened are lark bunting and horned lark. Scientists already know that the number of birds that survive to adulthood in grassland areas is very low and that the reason why may relate to differences in vegetation type. Scientists also know that the number of small mammals in a grassland area may relate directly to the number of nests that are invaded.

2002: International year of the mountain

Half of the fresh water that is consumed by humans comes from mountainous areas, and, mountains are home to one-tenth of the world's population. These days, mountain environments are of great interest in climate change studies because scientists have learned that their steep gradients make environmental changes easier to detect. Because of their importance, the year 2002 has been declared the International Year of the Mountain, and a number of studies are underway. One is the Global Observation Research Initiative in Alpine Environments, which monitors high-elevation vegetation responses to climate change. Based in Austria, the project monitors 65 sites in 31 countries. USGS studies some of these sites including ones in the Sierra Nevada, the Central and Northern Rockies and in the Olympic Mountains. USGS researchers have found that similar, decades-long climate changes have occurred in all of the U.S. regions they have studied.

Experimental fires have immediate impact on seed banks in Mojave Desert

The invasion of nonnative annual grasses along with a higher incidence of wildfires in Mojave Desert scrub communities has led to concern that native plant communities will be converted to nonnative annual grasslands. In an attempt to understand what the impact of this change could mean to desert communities, researchers at the USGS, Agricultural Research Service and the University of Nevada-Reno, quantified the effects of experimental fires on seed banks in the Mojave Desert of northwestern Arizona. The experiment was part of a larger study designed to understand plant community changes in response to wildfire, invasive annual grasses and seed-eating animals. Following brief, high-intensity burning of thirty 20 by 20 meter study plots, the researchers tested the seed banks by germinating seeds. The researchers were able to demonstrate that immediate changes occur in the demography of desert seed banks as a result of fires. They found that species richness was reduced by burning on an average of two to three species per plot.

Does more carbon dioxide mean more plants in the mojave? Should the native plants care?

The amount of carbon dioxide in Earth's atmosphere is expected to double before the end of the 21st century. The USGS and colleagues at the University of Nevada-Reno are attempting to determine if the higher levels of carbon dioxide will cause nonnative grasses to replace native grasses in the Mojave Desert. Arid ecosystems such as the Mojave are expected to have a greater increase in plant productivity than any other ecosystem as carbon dioxide increases in the atmosphere. This is because plants that are exposed to higher levels of carbon dioxide generally use available water more efficiently which in turn leaves more moisture available in the soil for other plants to use. In the Mojave, where water is typically limited, nonnative annual grasses may capture this surplus faster, leaving native species at a disadvantage. The growth responses of plants to elevated atmospheric carbon dioxide are complex, especially in natural plant communities where shrubs, grasses, and forbs compete to acquire limited soil moisture and nitrogen. Results of this research will determine whether differences in the responses of native and nonnative species to available moisture will influence future plant communities of arid systems.

Crust and dust: What makes the desert bloom?

In the desert, Mother Nature can do without a dust mop and still have a healthy house. According to USGS research, dust is an important element of the desert environment. Studies conducted in the desert of southeastern Utah indicate that dust furnishes essential nutrients, has an impact on water resources and soil and can be a factor that contributes to soil erosion. Soil crust adds to soil fertility by contributing newly fixed carbon and nitrogen and by trapping dust and stabilizing soil. When dust is added to the soil in an area, all of the necessary nutrients in the soil are increased. Dust may even be essential for plant growth. Some of the dust in southeastern Utah may have been transported long distances, perhaps from as far away as the Mojave in southern California. The data also indicate that dust sources may change through the decades and that human impacts may be responsible for those changes.

People or lightning? Fire in southwestern US, pre-1900

The view that most fires in the southwestern U.S. (chiefly Arizona and New Mexico) before 1900 were set by native peoples rather than caused by lightning appears to be inaccurate. The research of USGS ecologist Craig Allen indicates that while it is true that native peoples of the Southwest used fire for small-scale, local purposes such as clearing land to plant crops, there is insufficient evidence of fires deliberately set on a large scale. Rather, lightning may have been the chief cause of fires. Allen's examination of fire scar and climate records from tree rings, along with other indicators of ecological history, show conclusively that prehistoric fire patterns are very similar to modern observations of fires started by lightning. Allen also states that eyewitness accounts of Indian burning are rare and that the substantial archaeological and ethnographic data available in the Southwest reveal little indication of large-scale fires being deliberately set.
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News Release
U.S. Department of the Interior
U.S. Geological Survey
119 National Center
Reston, VA 20192


Find out how USGS scientists are using artificial nests and clay eggs to explore these factors at a lecture entitled "The Role of Small Mammal Predation on Nesting Success of Grassland Nesting Birds," by USGS wildlife biologist Thomas R. Stanley of Ft. Collins, Colo., at the annual Ecological Society of America meeting in Snowbird, Utah, Sun., Aug. 6, 2000, at 10:30 a.m. in the Superior Room of the Cliff Lodge in Snowbird.

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Thirteen-lined gray squirrel

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Horned lark nestlings

Thomas Stanley may be reached at tom_stanley@usgs.gov or 970-226-9360.

Find out more about the increasing importance of mountain areas in climate change as well as the International Year of the Mountain at a lecture by Daniel B. Fagre, USGS ecologist in West Glacier, Mont., entitled "Taking the Pulse of Mountains: Research and Monitoring Networks," part of Symposium # 2: Stressors in Western Mountain Ecosystems: Detecting Change and Its Consequences, at the annual Ecological Society of America meeting in Snowbird, Utah, Sun., Aug. 6, 2000, at 11:15 a.m. in Ballroom II of the Cliff Lodge in Snowbird.

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Daniel Fagre may be reached at dan_fagre@usgs.gov or 406-888-7993.

USGS ecologist Todd Esque of Las Vegas, Nev. and colleagues J.A.Young of the Agricultural Research Service in Reno, Nev. and C.R. Tracy of the University of Nevada-Reno, will give a lecture on this subject entitled "Seed Bank Responses to Experimental Fires in a Mojave Desert Scrub Community," at the annual Ecological Society of America meeting in Snowbird, Utah, Mon., Aug. 7, 2000 at 11:45 a.m. in the Maybird Room of the Cliff Lodge in Snowbird. The lecture is part of Oral Session #22 on Multiple Disturbance Effects, Including Fire.

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Contact Todd Esque at todd_esque@usgs.gov or 435-688-3215.

Find out more about how native plants react to increased levels of carbon dioxide and nonnative plant invaders at a lecture entitled "Plant Interactions in the Mojave Desert When Exposed to Elevated Atmospheric Carbon Dioxide During a Year With Above-Average Precipitation," by USGS plant ecologist and University of Nevada-Reno doctoral student Lesley DeFalco and Professor Robert Nowak of the University of Nevada-Reno at the annual Ecological Society of America meeting in Snowbird, Utah, on Mon., Aug. 7, 2000, at 1:45 p.m. in the Superior Room of the Cliff Lodge in Snowbird. The lecture is part of Oral Session #30: Effects of Elevated Carbon Dioxide.

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Lesley DeFalco collects measurements while perched above Mojave Desert plants at the Nevada Desert FACE (Free Air CO2 Enrichment) Facility in southern Nevada. The suspended platform allows scientists to easily access plants while studying the effects of elevated carbon dioxide, while fragile desert soils and plants remain undisturbed in their natural habitat.

Lesley DeFalco may be reached at lesley_defalco@usgs.gov or 702-914-2206, extension 229.

Find out more about dust, crust, and the desert at a lecture by USGS research ecologist Jayne Belnap and her colleagues R.L. Reynolds, M. Reheis, and S.L. Phillips of Moab, Utah, at the annual Ecological Society of America meeting in Snowbird, Utah, Sun., Aug., 6, 2000 at 2 p.m., in the Maybird Room of the Cliff Lodge in Snowbird.

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Scanning electron microgram of crust material sticking to sand grains.

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Crusts generally cover all soil spaces not occupied by vascular plants, which may be 70 percent or more of the living cover.

Contact Jayne Belnap at jayne_belnap@usgs.gov or 435-259-8628.

Learn more about what this part of North America was like before the Europeans at a lecture entitled "The Relative Roles of Lightning and Aboriginal Ignitions in Pre-1900 Fire Regimes, Southwestern U.S.," by USGS ecologist Craig Allen at the annual Ecological Society of America meeting in Snowbird, Utah, on Mon., Aug. 7, 2000, at 9:30 a.m. in the Maybird Room of the Cliff Lodge in Snowbird. The lecture is part of Oral Session #22: Multiple Disturbance Effects, Including Fire.

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Craig Allen may be reached at craig_allen@usgs.gov or 505-672-3861 extension 541.

US Geological Survey

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