Jornada Trails

Contents:

• Jornada Results Presented at Nairobi Meeting
  
• Geostatistics Work Appears in Ecology
  
• Friends of Jornada Symposium Set
  
• NSF Awards Grants for Two Cross-Site Studies at Jornada
  
• Duke Grad Student Awarded ESA Grant
  
• Book Review: Sonoran Desert Shrubs
  
• Featured Investigators: Athol Abrahams of SUNY-Buffalo and his team
  

Jornada Results Presented at Nairobi Meeting

Jornada investigators were asked to present a keynote paper at the international UNEP conference, Combating Global Warming by Combating Land Degradation. This meeting brought twenty specialists from nine countries to Nairobi, Kenya, for a week-long workshop in September of last year.

Sean Connin presented the Jornada results in a paper entitled "Dynamics of Carbon Storage in Degraded Arid Land Environments." He reviewed changes in the total amount of carbon stored in vegetation and soils in the Jornada basin by comparing the carbon content of present-day grasslands to that held in shrubland ecosystems. Surprisingly, there has been little overall change in carbon storage during the last 100 years.

The Jornada results were particularly relevant to the conference because various scientists have suggested planting shrubs in arid lands as a means of sequestering carbon dioxide from the atmosphere. But Connin and his coworkers concluded that "soil carbon storage through halophyte production, related energy costs, and landscape disturbance associated with cultivation indicate that arid land crop management offers little potential to mitigate rising atmospheric CO2 concentrations."

The conference proceedings, with this paper, will be published next year by the University of Arizona Press.
Contributed by Sean Connin, Dartmouth College

Geostatistics Work Appears in Ecology

One of the basic postulates of the Jornada LTER research program is that the invasion of desert grasslands by shrubs results in a change in the spatial heterogeneity of soil nutrients. The resulting "patches" of nutrient-rich soil become favored sites for the regeneration and persistence of shrubs in the desertified landscape.

Jornada investigators William H. Schlesinger, Jane A. Raikes, Anne E. Hartley, and Anne F. Cross provide a much-needed test of this hypothesis in research reported in the March 1996 issue of Ecology. These researchers used geostatistics to show the scale of soil nutrient patches in adjacent grassland and shrubland habitats in several areas of the desert Southwest. Their study examines nutrient distributions at three sites in the LTER network--the Central Plains grassland (CPR), the Sevilleta (SEV), and the Jornada (JRN)--as well as sites in the Mojave Desert of California and the Great Basin Desert near Reno.

For sites located in New Mexico, the team found that a non-essential plant nutrient, chloride, is distributed randomly in all communities, whereas in shrublands, soil phosphorus shows marked patches in its spatial distribution that are associated with the average size of creosotebush. In shrublands, the spatial distribution of soil nitrogen is also strongly related to the size and distribution of shrubs.

The development of soil patchiness is less extreme in the recently desertified habitats of the Chihuahuan Desert than in the more arid Mojave Desert.

Surprisingly, patchy nutrient distributions were found at the CPR as well, but the scale of patchiness is fine-grained and apparently associated with the size of clumping in the bunch grasses.

Friends of Jornada Symposium Set

The Annual "Friends of the Jornada" symposium will be held at New Mexico State University on May 23, 1996. This year, returning to its traditional format, the symposium will feature a day-long slate of research presentations by Jornada investigators and their students, followed by an evening barbecue at the Headquarters of the USDA Jornada Experimental Range. Speakers will make informal presentations about their latest research findings and their ideas for future summer study.

There is a registration fee of $5.00. For further details, contact Kris Havstad (Khavstad@nmsu.edu) at the Jornada Experimental Range.

NSF Awards Grants for Two Cross-Site Studies at Jornada

Two proposals involving the Jornada LTER site were successful in last fall's NSF competition for cross-site studies. With nearly $200,000 of new funding from NSF, Jornada investigator David Lightfoot will extend his studies of the effects of small mammals on desertification by establishing a site for comparative studies in Mapimi, Mexico.

Dave is testing the hypothesis, first proposed by Jim Brown at the University of New Mexico, that the exclusion of kangaroo rats from desert shrublands allows arid grasses to recolonize former grassland habitats. His work involves extensive areas of rodent exclusion at the Jornada and Sevilleta LTER sites. Similar study plots will now be established in Mexico.

Separately, John Wiens of Colorado State University was awarded $200,000 to begin comparative studies of ant communities at the Central Plains, Sevilleta, and Jornada LTER sites. John's studies will examine the changes in ant community structure that accompany changes in the spatial distribution of soil resources in grassland and shrubland habitats.

Duke Grad Student Wins ESA Grant

After our last issue went to press, Jornada Trails learned that Adrienne Pilmanis, a graduate student in botany at Duke University, received a $1000 award from the Ecological Society of America.

The award was made from the Society's Forrest Shreve Fund to support student research in the desert Southwest.

Adrienne is examining changes in the distribution of soil nutrients that accompany fires and the invasion of mesquite in desert grass-lands at the Jornada. She began her work in the summer of 1995 and will visit the Jornada again this year.

Book Review: Sonoran Desert Plants

Turner, R. M., J. E. Bowers, and Tony L. Burgess. 1995. Sonoran Desert Plants: An Ecological Atlas. University of Arizona Press, Tucson. 1-800-426-3797. xvii + 504 pp., illus., $70.00.

All serious desert ecologists will want to own this long-awaited volume by Ray Turner and his coworkers at the Desert Lab in Tucson. Many of the Sonoran species are also found at the Jornada, making the book essential for students of the Chihuahuan Desert as well.

For each species, Turner et al. provide a brief description of its field ecology and distribution, a range map compiled from herbarium specimens and published sightings, and a graph showing the distribution of each record as a function of altitude. These will provide a cornucopia of ideas for field physiological studies to understand the controls on plant distribution. Looking at these maps, it takes little imagination to see how global climate change may impact vegetation in the desert Southwest.

Featured Investigators: Athol Abrahams of SUNY-Buffalo and His Team

This issue of Jornada Trails recognizes the research team of Athol D. Abrahams (SUNY- Buffalo), Tony Parsons (U. Keele, UK) and John Wainwright (King's College, London) as its featured investigators. Working together for many years at the USDA's Walnut Gulch research station in southeastern Arizona, these workers are recent additions to the Jornada LTER team. They hope to extend their studies of runoff and sediment transport to a broad area of the desert Southwest.

Athol and his coworkers are the authors of a late-1995 paper in Geomorphology that shows that the invasion of desert grasslands by shrubs causes increased erosion from the "interrill" areas, by decreasing resistance to overland flow. This erosion increases the spatial heterogeneity of nutrients in desert soils.

Last summer, Athol and his coworkers performed a number of rainfall simulation experiments at the Jornada, in which the runoff waters were collected for measurements of the loss of nitrogen, phosphorus and other soil nutrients from soils in grassland and shrubland habitats.

The Jornada welcomes these prolific and talented scientists as co-investigators on its current LTER grant.

The newsletter Jornada Trails is published twice annually, in March and September. If you would like to contribute story ideas, or for more information on how to receive the printed newsletter, contact Bill Schlesinger.