Several populations of Rhus glabra were studies to assess the effect of fire on productivity, biomass allocation, N and chlorophyll content, and seasonal water relations in a North American tallgrass prairie. Compared with shoots in unburned prairie, shoots from burned sites had reduced biomass and fewer leaves; however, a significant postfire increase in shoot density led to similar midseason leaf area indices for both populations. Productivity was greater in the unburned population principally because of the biomass of sexual reproductive structures, which were absent in the resprouting shoots. However, burned populations allocated a greater proportion of biomass to leaves and wood, utilized for vertical growth, than unburned populations. Leaves in unburned prairie had greater stomatal density, specific leaf mass, and chlorophyll and N content than leaves from the burned population. For much of the growing season, stomatal conductances were greater in unburned prairie. Despite lower soil water potentials at the burned site, differences in midday leaf water potentials were small between populations; hence, differences in N content probably contributed more to the responses. The postfire reduction in productivity and sexual reproduction in R. glabra indicates that fire reduces its fitness