Abstract 9810414 Ebert Understanding why natural landscapes look as they do requires understanding how vegetation responds to unusual events. In the desert of southern California, rain typically is confined to winter months; occasionally, however, unusual late summer storms sweep up from the south. During the past 25 years there have been two of these unusual summer events: Hurricane Kathleen in 1976 and Hurricane Nora in 1997. In response to these events, seeds germinated for species that usually do not have new additions to their populations. Germination of seeds is just the first step in adding new plants to a population; they also must survive. The winter following Hurricane Kathleen was relative dry and seedling mortality was high. The winter of 1997-98 is during an El Nino and is proving to be much wetter. Seed germination following an unusual summer hurricane followed by high winter rains associated with an El Nino may prove to be the most important event of this century for many plant species in the desert. Our study of seedling growth and survival will help to understand the importance of rare events in ecosystems.
