Effects of a short-term freeze on Sphagnum girgensohnii grown under different light-temperature regimes

During the short, snow-free growing seasons in the Arctic, sudden “cold snaps” or freeze thaw events (FTE) frequently occur when temperatures fall subzero for 24 to 72 h. Vascular plants exposed to FTE are often irreversibly damaged, but despite their importance, the responses of nonvascular plants to FTE have been little studied. I grew plants of Sphagnum girgensonhii under high and low light and temperature conditions to investigate whether pre-freeze conditions influence damage and recovery of this important moss species. Plants grown at low light and high temperature showed the greatest growth. Upon freezing they also showed irreversible physiological damage and the greatest reduction in growth. Furthermore, some growing conditions resulted in increased production of new branches that were lost during freezing. The findings of this study suggest that the responses of Sphagnum species to climate variation may be important for the structure of arctic plant communities