My project aims to understand how the diversity and composition of grasslands changes from year to year with changes in rainfall and other environmental conditions. In particular, I would like to know whether years that are unfavorable for the majority of species, such as drier than average years, are predictably beneficial to a certain minority of species. For example, species that are poor competitors, but that are drought-tolerant, may benefit more from the reduction in competition with other species in a dry year than they are directly disadvantaged by the dry conditions. To the extent that this is true, then yearly variation in conditions contributes to the total diversity of a community, and this relationship is particularly important to understand given the recent anthropogenic increase in climatic variability and climatic extremes. The sites and data from this study will be made freely available to other researchers through several avenues. The study will support and train several personnel; my laboratory has an excellent record of training women and minorities as graduate students and post-doctoral researchers. The students employed by this project will contribute to environmental education programs at the McLaughlin UC Natural Reserve, which serves a community with many lower-income and minority students.