Chapter 15 - Long-term warming research in high-latitude ecosystems: Responses from polar ecosystems and implications for future climate
The aim of this chapter is to provide a synthesis of the findings from terrestrial warming experiments conducted in the Arctic and Antarctic. The Arctic is warming at twice the average global rate (Anisimov et al., 2007). The strongest warming rates worldwide occur in Siberia, northwestern Canada, and Alaska, and in the Antarctic, most notably the western Antarctic Peninsula. These systems are essentially the canaries of the coalmine, not only experiencing the strongest warming rates, but also being particularly sensitive to warming because of the limitation of many biological processes by low temperatures.First, we describe how terrestrial ecosystems in high-latitude biomes differ from ecosystems elsewhere. Then we examine experimental warming effects in the Arctic, with a focus on nonforested tundra landscapes. Next, we describe experimental warming methods and their challenges. We then review plant responses to warming, such as plant productivity and plant community dynamics to warming, and how these relate to soil nutrient availability. We transition to belowground responses of warming, including warming effects on the soil food web in the active layer (ground that thaws seasonally) of the soil profile. In the final portion of the Arctic section we discuss the implications of warming on the vast and vulnerable carbon stores in permafrost. We discuss the scale of the permafrost feedback to the global carbon balance using experimental data from Eight Mile Lake, Alaska, United States, with suggestions for improved quantification of temporal changes of carbon stores in permafrost.In the next part of the chapter we focus on Antarctica. We describe climatic and biological differences between the two principal regions on the Antarctic continent that contain field-warming experiments: the western Antarctic Peninsula and the McMurdo Dry Valleys, the largest ice-free area on the continent. We then describe the effect of warming in these two areas.In the final section of the chapter we draw parallels, but also describe differences, between the warming responses of the polar regions of both hemispheres. Taking into account the similarities and differences in responses to warming, as well as environmental and biological constraints, we then predict ecosystem trajectories under future warming scenarios for the Arctic and Antarctic. We conclude the section by synthesizing how changes in carbon cycling in the polar regions will feed back to the pace of planetary warming.