Jornada Trails

Contents:

• 1997 Friends of the Jornada Symposium
  What Makes a Desert?
  
• Jornada LTER Gets Good Marks in National Science Foundation Review
  
• Plant Biodiversity Experiment Yields Early Results
  
• Featured Investigator: Dale Gillette of NOAA
  
• Recent Publications from the Jornada
  

1997 Friends of the Jornada Symposium

What Makes a Desert?

When most people take a walk in the desert surrounding Las Cruces, they see only sand, occasional shrubs, and tenacious critters. Laura Huenneke sees a creeping process shaped by wind, water, fungus and footsteps.

She calls what she sees desertification.

Huenneke, an associate professor of biology at New Mexico State University, is a coinvestigator of the Jornada LTER, located about 20 miles northeast of Las Cruces.

Through the Jornada's archives, managed by Kris Havstad of the USDA’s Jornada Experimental Range, she has access to photographs taken 100 years ago showing that much of the land we now know as desert was once grassy and lush. Part of her job is to find out what happened, and why. But the more important task, she said, is to restore some aspects of the grasslands and their ecological functions.

"So many things have changed over the past century," Huenneke said, "including land use, increased carbon dioxide in the atmosphere, new seed sources, and the elimination of predators and prairie dogs by people, that it's hard for us ever to say what single thing may have caused desertification. Instead, we're focused on understanding today's systems and how we might best manage them in their current conditions."

In that quest for knowledge and results, Huenneke and other researchers from around the world are studying the Jornada range, looking at drainage patterns, weather conditions, and the collective impact of such things as wind, water, grazing, and human intrusion.

What they're finding indicates that deserts are formed when shrubs--like mesquite, creosote, and tarbush--take root in grassy areas. As the shrubs grow, they accumulate resources once distributed evenly within the grasslands. And soon, Huenneke said, the grass dies out and the shrubs take over, establishing "resource islands" that drastically alter the landscape.

In an effort to better understand these resource islands and the forces that come together to form them, NMSU has teamed up with Duke University and the USDA to form the LTER consortium at the Jornada, funded by the National Science Foundation.

The Jornada LTER been host to seven annual symposia, where researchers from NMSU, Duke, and other universities come together to discuss their research on desertification and to share their understanding of the grasslands-to-desert evolution.

The 1997 symposium, held July 10 on the NMSU campus, brought together more than 125 people to hear 21 presentations concerning ongoing research into the process of desertification and its consequences.

Huenneke said the interdisciplinary approach to studying the Jornada is helping scientists understand how desertification happens and what the consequences may be.

By understanding the process by which resource islands are formed in the first place, there may also be some hope, she said, for appropriate management of grasslands in New Mexico (and elsewhere) that might be in danger of desertification.

by Jess Williams, New Mexico State University News Service.

Jornada LTER Gets Good Marks in National Science Foundation Review

This summer, the National Science Foundation sent a team of six scientists to provide an objective outside review of the Jornada LTER research program.

Arriving on July 13, the team, headed by Scott Collins (NSF), spent two days touring key LTER research sites and listening to a variety of presentations on science and project management of the Jornada LTER program. In a break during an otherwise busy schedule, they dined on local beef at an evening barbecue at the headquarters of the Jornada Experimental Range.

The review team offered a number of useful comments on the Jornada LTER research program, but overall they were impressed by the strength of the conceptual framework for the field research and the excellent interactions between the LTER program and the Jornada Experimental Range of the Agricultural Research Service (USDA).

Particularly gratifying was praise for the data management program that has developed at the Jornada under the leadership of John Anderson of the department of biology. The review team also urged us to better integrate our disparate research activities.

The various comments of the review team will certainly guide our research efforts in the coming years and the preparation of a renewal proposal during the 1999–2000 academic year.

Plant Biodiversity Experiment Yields Early Results

In the fall of 1995, Laura Huenneke established the Plant Biodiversity Experiment as a long-term project of the Jornada LTER program. Replicate 25 x 25 meter plots in a diverse creosote shrubland were altered by removing plant species or plant functional groups in an attempt to assess the effect of these treatments on ecosystem function.

During summer 1997, two undergraduates in the NMSU/Howard University REU program, Heidi Bogner (from the University of Guelph) and Amber Rucker (from Southwestern University), examined patterns of animal activity in the experimental plots. Heidi observed significant differences among treatments in bird activity and in the use of the plots for perching and foraging. Amber found that rodent burrows did not differ among treatments, but soil disturbances created by foraging rodents were more abundant where shrub cover had been reduced.

For the past two summers, Michelle Zeisset, a master's student working with Huenneke, has examined grasshoppers and ants as part of the experiment. For both groups, functional or guild composition responded strongly to the experimental treatments. One striking result was an increase in numbers of bare-ground grasshoppers (including some potential pests) in plots where shrubs had been removed.

Michelle is working with Heather Miller, a Ph.D. student in Biology at NMSU, to describe the response of the vegetation to the alterations. By spring 1997, shrub cover had increased significantly where grasses or succulents had been removed, but perennial grasses did not show a similar response to shrub removal.

Ongoing work in the plots includes a survey of phytophagous insects on mesquite and creosotebush, carried out by a graduate student in entomology, and a study of growth and reproduction in mesquite and Opuntia by Maria del Carmen Mandujano, a postdoctoral associate from Mexico working with Huenneke. Heather Miller will examine nutrient cycling in these plots as part of her dissertation research.

Huenneke is excited about the potential of the experiment to yield insights about the effects of human alterations to plant diversity in semiarid ecosystems and eager to have more researchers capitalize on the establishment of this long-term experiment.
--Laura F. Huenneke, New Mexico State/Biology

Featured Investigator

Dale Gillette of NOAA

This issue of Jornada Trails recognizes the achievements of Dr. Dale A. Gillette and his contributions to the Jornada LTER program. Dale is one of the leading U.S. experts on the wind erosion of desert soils. Recently, his work has taken on special significance, because atmospheric dust is recognized to play an important role in determining the Earth's climate.

For many years, Dale was associated with the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. His work focused on the production, distribution, and fate of atmospheric aerosols--especially those derived from soils. In 1989 he organized an international project to examine the production of dust from seasonal, dry lakes in the U.S. and Russia. A primary research site was located on Owens Dry Lake in California.

In 1993, Dale moved to the Fluid Modeling Facility of the National Oceanic and Atmospheric Administration (NOAA) in Research Triangle Park, North Carolina. Shortly after that, he also joined our LTER team to examine how wind moves soils and generates the dunes that cover so much of the Jornada Basin. Dale works extensively with Jane Belnap (USGS) in his efforts to understand the role of soil crusts in preventing wind erosion.

Dale has established a long-term monitoring station for wind erosion just south of the headquarters of the Jornada Experimental Range. Shortly after it was operative, the station recorded a major wind and dust storm in the Jornada Basin (see Jornada Trails, October 1996). This event moved as much as 40 kg/m2 of soil materials.

Good natured and enthusiastic, Dale imparts his knowledge of wind erosion to all members of the Jornada LTER program. We are pleased to have him join our team.

Recent Publications from the Jornada

BassiriRad, H., J. F. Reynolds, R. A. Virginia, and M. H. Brunelle. 1997. Growth and root NO3- and PO43- uptake capacity of three desert species in response to atmospheric CO2 enrichment. Austrialian Journal of Plant Physiology 24: 353-358.

Chen, J.-L. and J. F. Reynolds. 1997. GePSI: A generic plant simulator based on object-oriented principles. Ecological Modelling 94: 53-66.

Connin, S. L., R. A. Virginia, and C. P. Chamberlain. 1997. Carbon isotopes reveal soil organic matter dynamics following arid land shrub expansion. Oecologia 110: 374-386.

Lauenroth, W. K., D. P. Coffin, I. C. Burke, and R. A. Virginia. 1997. Interactions between demographic and ecosystem processes: A challenge for functional types. pp. 234-254. In T. M. Smith, H. H. Shugart, and F. I. Woodward (eds.). Plant Functional Types. Cambridge University Press, Cambridge.

Peters, A. J., M. D. Eve, E. H. Holt, and W. G. Whitford. 1997. Analysis of desert plant community growth patterns with high temporal resolution satellite spectra. Journal of Applied Ecology 34: 418-432.

Reynolds, J. F. and B. Acock. 1997. Modularity and genericness in plant and ecosystem models. Ecological Modelling 94: 7-16.

Reynolds, J. F., R. A. Virginia, and W. H. Schlesinger. 1997. Defining plant functional types for models of desertification. pp. 195-216. In T. M. Smith, H. H. Shugart, and F. I. Woodward. (eds.). Plant Functional Types. Cambridge University Press, Cambridge.

Whitford, W. G., J. Anderson, and P. M. Rice. l997. Stemflow contributions to the “fertile island” effect in creosotebush, Larrea tridentata. Journal of Arid Environments 35: 451-457.