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NMSU Desert Research Has Worldwide Implications

LAS CRUCES - Before heading for work, Curtis Monger packs for the day -- a trowel, some common plastic bags, a sturdy straw hat and plenty of drinking water. While this New Mexico State University soil scientist's tools are simple, his work has implications for understanding one-third of the world's surface, which is covered by desert.

Monger, a researcher with NMSU's Agricultural Experiment Station, studies desertification at various sites in the Chihuahuan Desert, the largest desert in North America.

"Desertification refers to the decline in quality of vegetation and soil, such as the replacement of grass with desert shrubs," he said. "Desertification can be caused by environmental changes like a decline in rainfall or an increase in temperature; overgrazing; or even, as some experiments are showing, the increase of atmospheric carbon dioxide, which gives desert shrubs a competitive advantage over competing grasses-"

Monger says desertification can have devastating effects on the land and the people who live on the land. "This happened to a very profound extent around the Mediterranean," he said. "The Roman Empire, which was farming northern Africa, lost many of their productive agricultural lands due to desertification.

In that case, the changes from farmland to desert were caused by humans. Monger is interested in these human-induced changes, but also in the natural cycles of desertification. "If we can understand the natural cycles, we can get a better perspective of the impact that humans have contributed to modern desertification that we're seeing in the Chihuahuan Desert today."

He wants to know if deserts form and then become vegetative and then form again in a cyclic pattern.

He tries to find an answer in three ways. First, he studies erosion. "Erosion occurs whenever the ground is barren," he said. "If it's bare, the wind is going to blow the soil away, and the rain is going to wash it away." He tries to pinpoint when the erosion ocurred.

Then, he looks at pollen, which leaves a record of vegetative growth. "Pollen makes a wonderful fossil," he said. "Just like you can take an acorn and say this came from an oak tree, you can take a pollen grain and say this came from a creosote bush."

To find out what today's pollen has to say about vegetation, Monger scoops up small plastic bags full of soil and has the contents analyzed. At one study site at the USDA's Jornada Experiment Range located outside Las Cruces, he takes 30 samples in a 30-by-30- meter area four times each year. This site also is part of the National Science Foundation's Long-term Ecological Research project.

He'll then compare the modern pollen samples to fossil pollen buried in the soil from thousands of years past. At the Jornada, he can go back as far as 600,000 years by taking samples from a three -story-deep trench, built by the Nuclear Regulatory Commission in 1986. Monger calls the trench his time machine, because each buried land surface represents a specific time period.

Finally, he'll look at calcium carbonate crystals or caliche, which form in the soil of arid regions. This, too, tells a tale of changes in vegetation. "Different types of vegetation produce caliche crystals with specific isotope ratios," Monger said.

Putting all three types of data together, he'll try to reconstruct what has happened over time. "We need to get a sense of how fragile or how resilient these areas are to desertification," he said.

Monger thinks what he finds in the Chihuahuan Desert also could have implications for deserts elsewhere in the world. He plans to continue his work by studying deserts in South America.