Long-term effects of snowmelt timing and climate warming on phenology, growth, and reproductive effort of Arctic tundra plant species(1)

Arctic regions are particularly affected by rapidly rising temperatures and altered snow regimes. Snowmelt timing depends on spring temperatures and winter snow accumulation. Scenarios for the Arctic include both decreases and increases in snow accumulation. Predictions of future snowmelt timing are, thus, difficult and experimental evidence for ecological consequences is scarce. In 1995, a long-term factorial experiment was set up in a High Arctic evergreen shrub heath community on Ellesmere Island, Canada. We investigated how snow removal, snow addition, and passive warming affected phenology, growth and reproductive effort of the four common tundra plant species Cassiope tetragona (L.) D. Don, Dryas integrifolia Vahl, Luzula arctica Blytt, and Papaver radicatum Rottb. Timing of flowering and seed maturation as well as flower production were more strongly influenced by the combined effects of snowmelt timing and warming in the two shrub species than in the two herbaceous species. Warming effects persisted over the course of the growing season and resulted in increased shrub growth. Moreover, the long-term trend of increasing growth in two species suggests that ambient warming promotes tundra plant growth. Our results confirm the importance of complex interactions between temperature and snowmelt timing in driving species-specific plant responses to climate change in the Arctic.