It seems clear that a thorough knowledge of the biological details of the nitrogen (and especially phosphorus) cycles in this region may change attitudes toward mesquite and other seemingly useless components of the system. If mesquite is as expected, a major contributor of available nitrogen in the system, range management may become more compatible with wildlife management and biological conservation out of simple self interest.
Not surprisingly, the initial impulse of many, when learning of the nitrogen-fixing ability of mesquite, is to think primarily in terms of growing the plant as a crop (Felker and Bandurski, 1979). Research is then channeled toward genetic improvement (Felker, 1981) rather than ecology. In my opinion the first priority is to find out just how important mesquite is as a nitrogen source in this system. Given that information, the second priority should be to reevaluate existing range management procedures, integrating the positive input of mesquite into the economic analysis (e.g., Whitson and Scifres, 1980). I suggest that both ranching and the native biota of South Texas will benefit.
Finally, experimental manipulation, both basic and applied, must be carried out on longer time frames commensurate with the natural climatic cycles of the South Texas region. Research applied to the improvement of ranching should broaden its scope to include more basic questions about the whole system. Meanwhile, basic research in this northern piece of the Tamaulipan province must transcend compilation of species lists and autecology to face the big questions that dominate the biology and use of this region. The role of mesquite is perhaps the most obvious first question to ask, and proper inquiry will minimally involve exploration of nutrient cycles, insect-plant interactions, impact of drought, fire, and man (Figure 2). Comparisons with matched sites across the Rio Grande in Mexico should prove valuable in evaluation of the interaction of grazing and range management practices in the ecosystem, which "once provided the best wild pastures in the world." For a Texas naturalist, it is a pleasing thought that mesquite will be adding nitrogen to the soils of the Tamaulipan region when Texas oil wells are lost in history. It would be pleasing to a rancher to know how much will be added and under what conditions.