Climate change is shifting flowering dates in polar and temperate regions around the world, but we know relatively little about the demographic consequences of these shifted flowering times, especially whether there are consequences for population persistence. Plants that initiate life-cycle events earlier could be tracking their preferred climate conditions, which simply occur on an earlier calendar date under climate change. However, plants can also be exposed to novel environmental conditions when life-cycle events occur earlier, because different aspects of the climate are changing at different rates (for example, temperature and precipitation). We are experimentally causing plant life-cycle events to occur earlier by shifting spring snowmelt date in the Colorado Rocky Mountains (using black shade cloths on top of snow). We will track plant demographic vital rates (survival, growth, and reproduction) and phenology to compare plants that are early to control plants. This information will be incorporated into population models to determine how plant populations are affected by earlier life-cycle events, which is currently widely unknown.  (Iler)