SEEDLING GROWTH-RATE OF 3 SUBSPECIES OF BIG SAGEBRUSH

Over an extended period and in a non-water-limiting environment, the rate of seedling growth in Wyoming big sagebrush Artemisia tridentata ssp. wyomingensis approached zero and was less than that of seedlings of basin A.t. tridentata and mountain big sagebrush. A.t. vaseyana. Basin and mountain big sagebrush continued to have nonnegligible growth rates even at the end of the study. Wyoming big sagebrush reached its point of maximum growth rate c2 wk earlier than did the other 2 subspecies. It appears that Wyoming big sagebrush has evolved, placing 2 important growth characteristics under genetic control: 1) the maximum growth rate is attained earlier (when more water is available to sustain such growth) than in the other 2 subspecies, possibly enhancing its ability to survive on xeric sites during the early stages of growth; and 2) top growth produces smaller above-ground parts, enhancing survival after the early stages. -from Authors