Most of the grass species studied produced more and taller tillers subsequent to burning, so that shoot productivity is enhanced, with this stimulation sometimes persisting more than a decade. Possible stimulation of grasses by reduced competition from Artemisia tridentata in communities containing this fire-sensitive shrub is ruled out by the fact that the same grasses are equally stimulated in closely similar communities lacking the shrub. Fire may result in a major alteration of plant form, as in Agropyron spicatum, with tillers standing erect at first, then with marginal tillers bending centrifugally or centripetally across dead centers. What has long been described as 'burned out centers' in this grass proved to be an illusion, for the dead centers of large bunches are normally masked by standing litter plus new growth until after a fire. Except for an increase in the Ca content of Stipa comata shoots, chemical analyses of plant tissue, and bioassays of soil fertility showed no clear fire effects.