title: Circumpolar arctic tundra biomass and productivity dynamics in response to projected climate change and herbivory.
abstract: Satellite remote sensing data have indicated a general 'greening' trend in the arctic tundra biome. However, the observed changes based on remote sensing are the result of multiple environmental drivers, and the effects of individual controls such as warming, herbivory, and other disturbances on changes in vegetation biomass, community structure, and ecosystem function remain unclear. We apply ArcVeg, an arctic tundra vegetation dynamics model, to estimate potential changes in vegetation biomass and net primary production (NPP) at the plant community and functional type levels. ArcVeg is driven by soil nitrogen output from the Terrestrial Ecosystem Model, existing densities of Rangifer populations, and projected summer temperature changes by the NCAR CCSM4.0 general circulation model across the Arctic. We quantified the changes in aboveground biomass and NPP resulting from (i) observed herbivory only; (ii) projected climate change only; and (iii) coupled effects of projected climate change and herbivory. We evaluated model outputs of the absolute and relative differences in biomass and NPP by country, bioclimate subzone, and floristic province. Estimated potential biomass increases resulting from temperature increase only are approximately 5% greater than the biomass modeled due to coupled warming and herbivory. Such potential increases are greater in areas currently occupied by large or dense Rangifer herds such as the Nenets-occupied regions in Russia (27% greater vegetation increase without herbivores). In addition, herbivory modulates shifts in plant community structure caused by warming. Plant functional types such as shrubs and mosses were affected to a greater degree than other functional types by either warming or herbivory or coupled effects of the two.
authors.affiliation: Department of Geography, The George Washington University, 1922F street NW, Washington, DC, 20052, USA.
authors.forename: Qin
authors.identifier: 0000-0002-6693-7299
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Department of Environmental Sciences, University of Virginia, 291 McCormick Rd, Charlottesville, VA, 22904, USA.
authors.forename: Howard
authors.initials: H
authors.lastname: Epstein
authors.affiliation: Department of Geography, The George Washington University, 1922F street NW, Washington, DC, 20052, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Engstrom
authors.affiliation: Arctic Geobotany Center, University of Alaska, Fairbanks, AK, USA.
authors.forename: Donald
authors.initials: D
authors.lastname: Walker
mesh_terms: D001110:Arctic Regions; D018533:Biomass; D057231:Climate Change; D017753:Ecosystem; D060434:Herbivory; D012426:Russia; D065929:Tundra
keywords: arctic tundra; climate change; herbivory; net primary productivity; shrub expansion; tundra greening; vegetation biomass; vegetation dynamics modeling