Phreatic Tendencies of Exotic Grasses and Residual Species as Indicated by Radioisotope Absorption

Abstract

Rooting habits with respect to the capillary moisture zone above the watertable were studied by two methods: (1) absorption and translocation of radioactive isotopes and (2) direct observation of trench walls. Isotopes used were 131-I, 99-Mo, 51-Cr and 75-Se. In general, grasses appeared to absorb more actively in spring than in fall, and more from midlevel of the capillary zone than from the top or bottom. The highest activity was in foliage of intermediate wheatgrass which accumulated 75-Se from the watertable. While some injections resulted in no detected absorption, all grasses showed ability to pick up radioactivity at various levels in the capillary zone.