Variation in snow cover drives differences in frost resistance in seedlings of the alpine herb Aciphylla glacialis

Snow cover protects alpine plants from winter frost damage, keeping them under warmer and more stable temperatures than if there were no snow. Future climate scenarios predict less snow cover and earlier snow melt due to warming, causing paradoxically colder winters in a warmer climate. We compared intraspecific variation in cold tolerance between early snow melt (ESM) and late snow melt (LSM) populations of Aciphylla glacialis. Seedlings grown under common conditions were found to differ in cold tolerance consistent with their habitat of origin. ESM seedlings were more frost resistant and had a greater capacity to increase frost resistance in response to low temperatures than LSM seedlings. These results emphasise the relevance of microclimatic heterogeneity in driving physiological differences that might buffer some effects of climate change. Loss of snow cover could increase vulnerability of A. glacialis to lethal freezing in LSM sites whereas plants with greater frost tolerance in adjacent colder habitats (ESM sites) would be protected. Thus, intraspecific differentiation in tolerance of climatic stresses in combination with microclimatic refuges provided by topographic variation could enhance survival of some alpine species as climate warming progresses.