The Role of Mid-latitude Mountains in the Carbon Cycle: Global Perspective and a Western US Case Study

The International Geosphere Biosphere Program report on mountain ecosystems stresses the potential role of mountainous regions in the Earth’s geophysical cycles (Becker and Bugmann 2001). However, mountain environments have rarely been addressed specifically in studies of terrestrial carbon dynamics. Although it was first suggested that the US carbon sink was localized in eastern US forests (Fan et al. 1998), more recent studies that partition the US sink into specific regions suggest that a significant fraction is located in the western US (Schimel et al. 2000; Pacala et al. 2001 ; Schimel et al. 2002). As increasing development puts pressure on arable lands in North America and Temperate Asia, forests and other high carbon storage ecosystems are increasingly relegated to mountain landscapes. Inspection of recent land cover databases (e.g. IGBP or DeFries et al. 2000) shows clearly that in Temperate North America, Europe and China, a large fraction of forested landscapes is found in major and minor mountain ranges. Figure 1 shows an index of carbon uptake in forests based on forest cover from satellite observations (Defries et al. 2000) and growing season length (with longer growing seasons indicating a higher carbon uptake potential). Growing season lengths are scaled to eddy covariance estimates of carbon uptake per growing season day (Falge et al. 2002). Since the majority of current terrestrial sinks are found in the Northern Hemisphere mid-latitudes, montane forests have the potential to contribute significantly to current carbon sinks