During 1998–1999 a severe drought occurred in northwestern Patagonia that provoked an extensive wildfire. We monitored vegetation cover and the soil seed bank to study the diversity and functional group gap dynamics in burned and unburned sites. Species were grouped into 3 functional groups: forbs, fugitive species, and annual grasses. Post-drought vegetation recovered quickly due to a rainy spring in the second year but decreased after a dry and warm spring in the third year. These patterns underline the close relationship that exists between phenological phases and meteorological variables. Drought decreased richness but did not affect the presence of stress-tolerant species, whereas fire increased richness by allowing the establishment of fugitive species. Species in the fugitive functional group may be fire adapted and depend on seed accumulation in the seed bank (storage effect) to coexist with other gap species. Forbs exhibited their highest vegetation cover and seed bank density in the unburned site. Global climate change suggests an increase in the frequency and amplitude of El Niño/Southern Oscillation phenomena that, in northwestern Patagonia, are related to the occurrence of drought, fire, and changes in vegetation dynamics.

Nomenclature: Correa, 1969–1999.