Arctic tree-line response to 21st century warming is an important positive feedback mechanisms that can facilitate further tree line advance and amplify changes to the global heat budget through changes in the planetary albedo and effects on soil carbon pools. However, responses of the forest-tundra ecotone to the modern warming trend are spatially heterogeneous because controls other than temperature limit tree growth and seedling establishment near tree line. Paleo-investigations can address the sensitivity of the forest-tundra ecotone to external drivers by identifying factors that led to the establishment and persistence of modern vegetation composition. In contrast to many circumpolar regions that experienced advanced positions [...]
