Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model

Abstract

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 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 4 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 4 , may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.

Mapping Arctic Tundra Vegetation Communities Using Field Spectroscopy and Multispectral Satellite Data in North Alaska, USA

“…The fine-scale differences between the plant traits, community dynamics and spectral properties create the unique spectral signatures that allow each community to be differentiated. This can be especially useful as many areas of the Arctic are undergoing an increase in shrub-cover [13], allowing for potential mapping of this expansion, as well as partitioning vegetation community contribution to landscape level carbon budgets.…”

“…These changes influence the terrestrial carbon cycle and thus alter the relationship between arctic ecosystems and global climate. For example, an increasing growing season length can enhance carbon uptake through photosynthesis and thereby reduce atmospheric carbon dioxide (CO 2 ) concentrations [13]. Conversely, increasing temperatures may heighten methane (CH 4 ) and CO 2 release from thawing permafrost, enhancing plant-mediated transport of CH 4 [14,15] and contributing to rising levels of greenhouse gases in the atmosphere.…”

Biogeophysical feedbacks enhance the Arctic terrestrial carbon sink in regional Earth system dynamics

“…Hickler et al, 2012), and Arctic and Subarctic regions (e.g. Zhang et al, 2013). The performance and behaviour of the model in simulating ecosystem carbon cycle variations and responses to drivers has been highlighted, for example, by Ahlström et al (2012a, b), Piao et al (2013) and .…”

“…To evaluate net ecosystem exchange (NEE), the residual difference among the fluxes of NPP, HR and fire disturbance, we compared inter-annual variability of NEE anomalies and mean C budget for an Arctic tundra domain Fig. S1 in the Supplement) to the estimates of process-based models (LPJ-GUESS WHyMe (Wania et al, 2009a(Wania et al, , b, 2010Zhang et al, 2013). Terrestrial Carbon Flux (TCF) model (Kimball et al, 2009), OR-CHIDEE (Koven et al, 2009(Koven et al, , 2011, Terrestrial Ecosystem Model (TEM; version 6.03) (McGuire et al, 2010;Hayes et al, 2011) and inversion models for the period 1990-2006; for details also see the Appendix in McGuire et al (2012).…”

The Impact of Climate Change and Human Activity on Net Primary Production in Tibet

“…In contrast with evidence showing that vegetation resources are threatened by human population growth [6], a larger population might use vegetation resources more efficiently. A close connection exists between vegetation and human activity [34,35]. Furthermore, the impact of the percentage of human activity on NPP did not increase human-activity density such as in Lhasa.…”