10.6084/m9.figshare.1011560.v1 Wenxin Zhang Wenxin Zhang Paul A Miller Paul A Miller Benjamin Smith Benjamin Smith Rita Wania Rita Wania Torben Koenigk Torben Koenigk Ralf Döscher Ralf Döscher Tree-line IOP Publishing 2013 poleward advance vegetation shifts Hot spots future climate scenarios Hudson Bay heat flux latter land surface feedbacks ecosystem biogeochemical cycling dominance shift CH 4 emission carbon sequestration Arctic version CAVM forest phenology changes evergreen boreal conifer forest Wetland ecosystems 21 st century shrub tundra model Environmental Science 2013-08-29 00:00:00 Figure https://iop.figshare.com/articles/figure/_Tree_line/1011560 <p><strong>Figure 2.</strong> Tree-line. (a) The simulated tree-line comparisons between the CRU-forced run and the RCAO-forced run. (b) The recent and the future tree-line comparisons in the RCAO-forced run. (Green: the CAVM tree-line boundary; blue: tree-line advance for the latter; red: tree-line retreat for the latter; gray: no difference.)</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH<sub>4</sub> emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH<sub>4</sub>, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p>