Water stress of tallgrass prairie plants in central Oklahoma.

The predawn xylem water potentials of Andropogon gerardi, Schizachyrium scoparti, Panicum oligosanthes, Sporobolus asper, Ambrosia psilostachya, Psoralea tenuiflora and Sohwuun eleagnifolium were determined by the pressure equilibration chamber method during the 1980 growing season in a Central Oklahoma tallgrass prairie. Water potentials declined rapidly after June indicating high levels of water stress in all species. The decline in plant water potential for Schizachyrium scoparium, and to a lesser extent, Panicum oligosanthes, was much greater than that for ,the other 5 species. Andropogon gerardi apparently avoids dehydration by having a deep root system, whereas Schizachyrium scoparium survives in spite of a high degree of dehydration. Aboveground live biomasses declined sharply at about the same time plant water potential values decreased sharply. Results indicate plant water potential data are useful for interpreting range plant growth responses and predicting adaptability of species to harsh growing conditions.