Jornada Trails

Contents:

• Climate Variability Impacts Jornada Ecosystems
  
• Conference Participants Urge Ratification of U.N. Desertification Convention
  
• Students Participate in Jornada Programs
  
• Book Review: Physiological Ecology of North American Desert Plants
  
• Featured Investigator: Laura F. Huenneke
  

by Ross Virginia

Environmental Studies Program

Dartmouth College

More than 100 researchers, including students and representatives from public and private resource management agencies, convened on July 16 for the Eighth Annual Friends of the Jornada Symposium at New Mexico State University. Kris Havstad (USDA-ARS) and Bill Schlesinger (Duke University) welcomed the 16 symposium speakers and encouraged all to continue to make the Jornada one of the world’s leading aridland research sites.

John Wainwright from King’s College (London) opened the symposium with a comprehensive examination of climate and climate variability in the Jornada Basin reaching back to 1915. John’s work highlighted the special status of the Jornada as having one of longest continuous climate records of any aridland site in the world. Since 1915, the trend has been for increasing (0.8 mm/yr) rainfall, mostly in the summer, and a decrease in mean temperature, mainly since the 1940s. During El Niño years, there is a 150% increase in winter rain, but no change in summer rains. La Niña in our region produces dry winters (only 50% of normal rainfall) and little change in summer precipitation. These climate patterns and other cycles may underlie events such as the "Drought of the 1950s" that are thought to play a major role in the increasing success of shrubs on the Jornada in recent decades. John speculated that the ability of some shrubs to switch growth between winter and summer seasons (as shown from the recent Jornada rainout experiments) may explain the success of shrubs over grasses, whose growth is dependent on summer rains.

Ed Fredrickson (USDA-ARS) and Milt Thomas (NMSU) gave a tag-team presentation on potential improvements in aridland beef production. They made a strong case for the design of flexible grazing systems that prevent damage to rangelands during poor forage production years. In particular, ranch managers should consider the "match" between the animal and the physiological stresses imposed by the semiarid environment. Historically, we have used cattle breeds from temperate locales to graze in the hot and dry lands of the Southwest. Ed and Milt showed that a variety of smaller, lesser-known cattle that have been bred for centuries in arid lands may be better suited to beef production in the Chihuahuan desert. These include the Criollo cattle of Mexico and Latin America, Mashona cattle of southern Africa, and various Brahman breeds.

The impact of climate on the grassland-shrubland boundary was explored in a modeling study by Deb Coffin and Jeff Herrick (USDA-ARS). Their modeling framework centers on plant functional type responses to environment and soils, and the associated feedbacks. Climate change can be simulated over a 50-year period, and model runs of up to 700 years are possible. Their results suggest that plant life history traits (especially recruitment) are most important in determining the dynamic balance between grass and shrub functional types on sites with good soils. On degraded soils, soil development processes involving plants (including plant-driven changes in soil heterogeneity) determine the outcome. They plan to couple a nitrogen cycling model to the ECOTONE model to study the role of this limiting nutrient on ecosystem-level responses to climate.

The symposium closed with an invitation by Ross Virginia to consider the inter-site research opportunities provided by the McMurdo Antarctic LTER, which has replaced the Jornada as the most arid site in the network. Comparative studies of cold-dry and hot-dry habitats provide powerful contrasts in the functioning of arid lands throughout the world. The crowd adjourned for the traditional barbecue at the USDA Headquarters, drawing to a close another informative and happy gathering of Jornada friends.

Jornada Basin LTER principal investigator William Schlesinger gave a keynote address at a conference organized by the Smithsonian Institution, entitled "Combating Desertification: America’s Role in Ensuring the Future." Held on June 19 in Washington, D.C., this conference was organized to provide Congressional staff and government officials with basic knowledge about desertification as a global problem and to promote Senate ratification of the United Nations Convention on Desertification.

Schlesinger reviewed his work on the loss of soil nutrients that is associated with the transition between semiarid grasslands and desert shrublands in the Jornada Basin. He suggested that desertification events around the world may be associated with the transport and loss of soil nutrients by wind and water. Losses of soil nutrients are associated with the development of "islands of fertility" in shrub deserts. Schlesinger also suggested that the appearance of linear features—roads, power lines, aqueducts, etc.—in arid habitats may be a useful "leading desertification index" in many areas of the world. These linear features often disrupt the natural flowpaths of water that are essential to ecosystem function in arid lands.

Among others speaking to the conference were Dr. Patricia Jacobberger-Jellison, of the National Air and Space Museum, who emphasized the value of remote sensing for recording the desertification process in Africa. Dr. Uriel Safriel reviewed the success and failure of government policies striving "to make the desert bloom" in Israel during the last several decades, and Ms. Michele Leighton reviewed the work of the Natural Heritage Foundation to document recent desertification in Mexico.

After the conference, Schlesinger met with staff members of the Senate Committee on Foreign Relations, which will determine if the U.N. treaty should come before the entire Senate for a ratification vote. As a followup to the conference, he participated in a number of press briefings for Senate staffers, business leaders and the media in mid-September.

by Kris Havstad

U.S. Department of Agriculture

Agricultural Research Service

The staff of the Jornada Experimental Range has developed a variety of programs focusing on desert ecology for K-12 students and their teachers in southern New Mexico and west Texas. Within the past year, field activities for 2,500 students in groups ranging from 10 to 50 have been a core part of this effort.

Students visit sites in the Jornada basin to see studies of animal ecology, plant chemistry, photosynthesis, animal husbandry, soil morphology, and invertebrate ecology. All stations involve hands-on experiences and in some cases field measurements of selected biological properties. The program complements classroom demonstrations in local schools and student visits to the scientific facilities of New Mexico State University.

The Jornada Basin LTER is also in its second year of the First-Step Program, with funds provided by the National Science Foundation to the USDA’s Agricultural Research Service. In this program, local grade school science teachers spend a month working on desert ecology experiments at the Jornada. The emphasis is on developing affordable projects that elementary students can do in their classrooms. Four teachers participated in the First-Step Program in 1997 and six teachers in 1998.

A 960-acre easement has been officially granted by the USDA to the Chihuahuan Desert Nature Park, Inc. (CDNP), a non-profit organization devoted to environmental education for children and adults in the Las Cruces region. Coordinated by Peggy Logan, the CDNP is assuming some of the educational activities of the Jornada Basin LTER, primarily for K-12 students. The easement provides land adjacent to the Jornada Experimental Range for educational activities and for exhibits highlighting LTER and other activities.

by James F. Reynolds

Duke University

by S. D. Smith, R. K. Monson, and J. E. Anderson (Springer-Verlag, 1997)

This compact book contains a wealth of information. The authors’ stated goal is to examine the structure and function of North American desert plants from the perspective of growth forms. The first chapter is an excellent review of vegetation and physical environments of North American deserts. This overview is followed by a thorough treatment of plant adaptations, physiological processes (photosynthesis, nitrogen acquisition, water relations, etc.) and their responses to the stresses typical of arid ecosystems.

The authors place considerable emphasis on drought stress, reflecting their research expertise. The rest of the book surveys numerous case studies of the dominant growth forms of North American deserts, including evergreen shrubs (mainly Artemisia and Larrea), perennial grasses, phreatophytes, annuals, and exotics (e.g., Bromus tectorum and Tamarix). My only disappointment was that other species were not included as case studies.

For years, I’ve always considered Osmond, Bjorkman, and Anderson’s book, Physiological Processes in Plant Ecology, to be the best reference for the physiological ecology of desert plants. This new book by Smith, Monson, and Anderson now has that honor.

In this issue of Jornada Trails we recognize Dr. Laura F. Huenneke as our featured Jornada LTER investigator. Laura arrived at New Mexico State University as an assistant professor in 1987. Moving rapidly through the professorial ranks, she has just recently assumed the position of Chair of the Biology Department at NMSU.

A specialist in plant community ecology from her early days as a doctoral student at Cornell University, Laura directs the core-area measurements of net primary production in the Jornada LTER program. She also organized the long-term biodiversity experiment, in which various "simplifications" of plant community structure are made in replicate plots to examine the importance of plant diversity to ecosystem function.

Laura has worked closely with Dave Lightfoot (University of New Mexico) to establish ties with ecologists in Mexico. Their efforts have resulted in a number of cooperative experiments between the Mapimi Biosphere Reserve (Chihuahua, Mexico) and the Jornada Basin and Sevilleta LTER sites in New Mexico.

All those who have worked with Laura know of her love of the desert and her appreciation of the impact of human populations on desert ecosystems. During the past several years, Laura has represented the Jornada Basin LTER at several meetings of the International Geosphere Biosphere Program (IGBP), speaking on the impacts of plant invasions and losses of biodiversity in desert ecosystems worldwide.

Laura offers a cordial welcome to all those who come to Las Cruces to visit the Jornada for science or pleasure. In Fiscal Year 2001, she will assume the role of principal investigator of the Jornada Basin LTER, upon its next scheduled renewal by the National Science Foundation. We look forward to working with her as our LTER site enters its third decade.