Many forests, including the mixed-conifer forest of the Sierra Nevada, California, historically experienced a fire regime that generated considerable within- and among-fire environmental variability. Fire suppression has resulted in a heavier, more continuous fuel bed, which can cause today's prescribed fires to be considerably more homogeneous. To evaluate the potential importance of variability in fire severity on post-fire plant communities, I conducted an experiment to test whether understory species respond differently to sites burned under a heavy fuel load versus sites that burned under a light fuel load. Woody fuel was added or removed from small forest plots in order to manipulate the fire severity during prescribed fire. The fuel load manipulations affected which species survived fire as well as which species germinated after fire. Seven species (Chimaphila menziesii, Chrysolepis sempervirens, Osmorhiza chilensis, Pyrola picta, Phacelia hydrophylloides, Rubus parviflorus, and Smilacina racemosa) were unable to survive fire in either treatment. Four species (Bromus laevipes, Galium sparsiflorum, Rubus glaucifolius, and Symphoricarpos mollis) survived more often on sites that were burned under a light fuel load. Several fire-stimulated species (Calystegia malacophylla, Cryptantha sp., Gayophytum eriospermum, Solatium xanti, Arctostaphylos patula, Ceanothus parvifolius, and Lotus crassifolius) germinated after fire regardless of fuel load, but others (Claytonia perfoliata, Ceanothus cordulatus, Prunus emarginata, and Ribes tularense) appeared more often on the light fuel treatments. Seedlings of Abies concolor germinated more often on the sites that burned under heavy fuel conditions. The varying responses of different species suggest that small-scale variations in fuel load may cause heterogeneous patterns of surface fire severity, which in turn may contribute to maintaining floral diversity in the mixed-conifer forest understory. In order to conserve native understory plant diversity, fire management efforts to restore these forests might consider spatial heterogeneity in fire severity as a management objective.