Emissions of greenhouse gases are expected to raise global mean temperature over the next century by 1.0-3.5 °C. Global warming trends are amplified at high latitudes because heating converts high-albedo (reflective) ice and snow surfaces to dark absorptive surfaces that absorb more solar energy and transfer it to the atmosphere. Furthermore, scientists have argued that ecological responses to this recent climate change will be complex and varied. For example, the warming of the Alaskan Arctic during the past 150 years has accelerated over the last three decades and is expected to increase vegetation productivity in tundra if shrubs become more abundant. In order to investigate how tundra vegetation may respond to increases in temperature and snow cover that could result as a consequence of the Arctic amplification, we used 1m² open-topped fiberglass chambers (OTC’s) combined with large snow fences to artificially warm and modify winter snow regimes of a series of permanent vegetation plots established in Toolik Lake, Alaska. Fieldwork consisted in measuring the vegetation growth and height of plant species in these plots using the point-frame method. The snow cover and temperature manipulation was done in two ecosystem types, dry heath tundra and moist tussock tundra.

Results/Conclusions

Results show that after 14 years of manipulating snow regime and temperature of the vegetation at our two experimental sites, plant communities have responded drastically to manipulations but mainly in response to the changes in the snow conditions. Findings at the moist site further support the importance of snow in regulating plant community patterns in the Alaskan tundra; however, results from an NPMANOVA revealed that temperature was also an important influence in the determination of the particular community structures at the plots. Therefore, major changes in plant community composition are expected to result as a consequence of a hypothesized warmer and wetter future climate scenario in both Arctic dry heath and moist tussock tundra. A higher influence of increasing temperature on moist tussock tundra plant communities will have serious implications to the arctic carbon balance as soil carbon stocks are greatest in tussock tundra that forms on stable, gentle slopes withrelatively shallow thaw like the one present in our site.