Vulnerability of wild American ginseng to an extreme early spring temperature fluctuation

Frost events in natural plant populations can have dramatic demographic consequences. For many plant species, spring emergence occurs when probability of damaging frost is low. Climate change, however, may alter weather patterns such that the environmental cues signaling spring emergence no longer coincide with periods of low frost risk, rendering plant populations susceptible to damaging frost events more frequently than in the past. In 2007, a spring freeze occurred in the eastern United States after a period of unusually warm temperatures. We took advantage of a long-term demographic dataset for American ginseng (Panax quinquefolius L.) to examine among and within population patterns of frost damage, as well as the effects of the frost on ginseng demography. Higher temperatures prior to the frost event increased the probability and extent of frost damage at the population level. Within populations, large plants tended to be damaged more frequently than smaller plants. Survival, growth, and reproduction were reduced in frost-damaged plants compared to undamaged plants in the year of the frost event, and negative effects on growth and reproduction persisted the following year. For plants such as ginseng, increases in frost frequency will negatively impact population growth, and likely have serious ramifications for long-term population viability.