LITTLE ICE-AGE TEMPERATURE ESTIMATED BY GROWTH AND FLOWERING DIFFERENCES BETWEEN SUBFOSSIL AND EXTANT SHOOTS OF CASSIOPE TETRAGONA, AN ARCTIC HEATHER

1. A unique opportunity to study conditions for plant growth at the onset of glaciation was offered as a retreating glacier at Ellesmere Island, Canada, revealed well-preserved, subfossil plants (411+/-70 radio-carbon years old) of Cassiope tetragona, an arctic dwarf-shrub previously used to study climate-related growth of modern plants. 2. Growth and flowering of the ancient and modern shoots of C. tetragona from the same locality were examined retrospectively. The ancient shoots produced leaves in each, and flowers in each except one, of the last 26 years before they died, although this production was significantly lower and less variable among years than in the modern shoots. 3. Predictions based on regression between modern plant performance and climatic data from the study site imply that the mean July temperature of the period immediately preceding the glaciation of the area was about 0.7 degrees C lower than today, This estimate is independently supported by the correlation between growth and mean July temperature seen today among different sites. 4. The results support the idea that the pre-little Ice Age plants were killed suddenly by permanent snow embedment and not by glacial movements or temperature limitations as such.