The dynamics of the grass Danthonia spicata were studied in five sites in a pine-hardwood forest undergoing secondary succession in northern lower Michigan. The five sites had last been burned in 1980, 1954, 1948, 1936, and 1911, respectively. Total population size, number of seedlings, adult survivorship and seedling survivorship were monitored by mapping quadrats from 1982-1985. Adult survivorship was also measured by marking individuals and observing their fates from 1980-1985. Fifty individuals in each site were measured for size, relative reproductive effort and survival. Population size rose rapidly following clear-cutting and fire, and slowly declined between 30 and 70 years following disturbance. One-half of each population, on average, dies every 2.2 years. The number of seedlings and total population size varied significantly among census years. Seedling survivorship and adult survivorship did not vary significantly. Number of seedlings, total population size and adult survivorship varied significantly among sites of different successional age. Seedling survivorship did not vary significantly. Adult survivorship increased with increasing size and decreased with increasing relative reproductive effort. Changes in population size in these sites were controlled by genetic and environmental changes, especially the size and number of patches with high light levels. The long-term dynamics of these populations cannot be predicted by extrapolating from short-term measurements.