The Jornada LTER has experienced a major change in principal investigators and a modification of program objectives. In January 1988, four new P.I.s joined the Jornada team: Dr. William Schlesinger (Duke University); Dr. Wesley Jarrell (University of California-Riverside); Dr. Ross Virginia (San Diego State University); and Dr. Laura Huenneke (New Mexico State University).
Dr. Schlesinger has been conducting research on nutrient cycling processes at the Jornada for several years and has been an informal participant in the Jornada LTER program since its beginning. Bill will be expanding his studies of denitrification and initiating work on ammonia volatilization in the summer of this year. Drs. Jarrell and Virginia have been conducting research on N-fixation in deep rooted legumes and on rhizosphere processes in deep rooted shrubs. They are expanding their efforts to examine soil organic matter dynamics utilizing natural abundance ratios of stable isotopes in addition to other techniques. Because Dr. Peter Wierenga will be leaving the Jornada LTER program to take a position as head of the soils department at the University of Arizona, Wes and Ross will assume responsibility for the soil water studies. They plan to expand their root studies using mini-rhizotions to obtain data on root growth and root turnover. Our current studies have shown that deep rooting is not limited to mesquite, Prosopis glandulosa. Other shrubs may have viable roots at depths of 5-7 meters which imposes logistic constraints on root studies of such species.
Dr. Huenneke is a recent addition to the biology faculty at NMSU. In addition to continuing some studies in collaboration with Hal Mooney at Stanford where she was a post-doc, Laura is setting up long term demographic studies of several shrubs plus collaborating on primary productivity studies and studies of the effects of soil disturbance by animals.
Dr. James Reynolds, who joined the Jornada LTER in 1985, is modifying his modelling work which has focused on primary production, decomposition, and nitrogen cycling processes to incorporate spatial patterns using a dynamic geographic information system approach. Jim is currently director of Systems Ecology at San Diego State University.
Dr. Tim Ward, collaborating hydrologist, and Sue BoIn have been analyzing infiltration and run-off data as part of their hydrological studies. They found that run-off was a function of storm energy nt vegetative cover, for virtually all of the storms that we experienced on the Jornada since 1980. Thus one more conventional idea must be modified when applied to desert ecosystems.
The modification of program objectives is a change from focusing on hypotheses built around temporal and spatial variability with work focused on a single watershed to hypotheses built around the concept that desertification has changed a previously uniform distribution of resources to a patchy distribution of resources. We hypothesize that this shift in distribution of resources has disrupted temporal linkages among ecosystems and ecosystem processes. In order to address questions concerning desertification processes, we have set up research at several new locations on the Jornada and are working to increase collaborative efforts with the USDA programs at the Jornada.
Additional information may be obtained by contacting Dr. Walt Whitford, Dept. of Biology, New Mexico State University, Las Cruces, NM 88003.