The daylong series of research presentations brought more than 100 researchers to the New Mexico State University campus June 24, 1999. Bill Schlesinger opened the morning session with a paper on the relationships between vegetation cover, albedo, and radiant temperatures in arid and semiarid lands of the Chihuahuan desert. As ground cover decreases, radiant land temperature and albedo increase. Satellite imagery detected lower vegetation cover in Mexico, as the result of overgrazing, which showed up as increased temperatures and albedo.
Greg Okin, (California Institute of Technology), described his studies of advanced remote sensing of semiarid grasslands at the Jornada to detect vegetation types, living versus dead vegetation, gravel-sand-clay content, iron oxidation, and land surface disturbance. High spectral resolution from AVIRIS can be used to recognize different ecosystems in the central Jornada Basin. Al Rango described how the JORNEX project has produced detailed topographic maps of the morphology of mesquite dunes, using remote sensing techniques, such as scanning laser and video data. His maps of coppice dunefields have a vertical resolution of 10 cm and a horizon resolution of 1 meter.
Among other papers, Laura Huenneke described patterns of aboveground plant production in the Jornada from 1989 to 1999. Her data revealed three patterns:
- Shrublands and grasslands have similar amounts of aboveground biomass and net primary production (NPP)
- Biomass distribution is more patchy in shrublands than in grasslands
- Grasslands have greater temporal variability in NPP than shrubland
Walt Whitford spoke on his long-term studies of the establishment of Larrea tridentata in semiarid grasslands. He tracked the survival of creosote bush seedlings planted in control plots, in irrigated plots, and in irrigated plots with nitrogen. Early in the experiment (1984), many seedlings survived in the control and in the irrigated plots with nitrogen, but by 1986 no seedlings survived, and even the control contained few surviving seedlings. The high mortality rate was attributed to rabbits, other rodents, and damping-off.
Later, Dave Lightfoot spoke of his research of the interactions between rodents, plants and ants, which is conducted at the Sevilleta and Jornada LTER sites and the Mapimi Biosphere Reserve in Mexico. At several sites, more fluff grass is visible inside rodent exclosures because the plants reach greater heights when they are not grazed. This gives rise to more seed-harvester ants because the fluff grass provides them with a food source.
The Symposium closed with a presentation by Ed Fredrickson and Kris Havstad, who reviewed the history of livestock grazing in the Jornada basin, including the impacts of the Pleistocene megafauna, the Spanish introduction of grazing animals, and populations of grazing animals at the Jornada from the late 1800s to present. They pointed out the economic difficulties facing ranchers, who must contend with fluctuations in forage biomass and constant mortgage payments. They described how management practices in the future may include diversifying forage, decreasing forage demand, basing management on ecological principles, and developing economic flexibility.