EXPLOITATION OF PHOSPHATE FROM FERTILE SOIL MICROSITES BY 3 GREAT-BASIN PERENNIALS WHEN IN COMPETITION

The effectiveness of phosphate (P) exploitation from fertile soil microsites was investigated with a dual-radioisotope approach for three perennial Great Basin species. Three experiments with competing species pairs assessed the ability to acquire P in fertilized and control patches. The patches occupied less than 1 % of the rooted soil volume. In all experiments, the plants acquired at least as much radioisotope from the enriched as from the control patches even though the isotopes in the enriched patches were diluted by a factor of 10(8) with added P-31. The plants procured P from the enriched patches in proportion to its increased concentration relative to P in the control patches. The relative ability of the competing species to acquire P was very similar in control and enriched patches. Artemisia tridentata (Rydb.) Beetle was able to acquire much more P than Pseudoroegneria spicata (Pursh) A. Love and was equivalent in ability to acquire P when in competition with Agropyron desertorum (Fisch, ex Link) Schult. However, when the Agropyron and Pseudoroegneria were together, they were unexpectedly similar in procuring P.