title: Historical and projected trends in landscape drivers affecting carbon dynamics in Alaska.
abstract: Modern climate change in Alaska has resulted in widespread thawing of permafrost, increased fire activity, and extensive changes in vegetation characteristics that have significant consequences for socioecological systems. Despite observations of the heightened sensitivity of these systems to change, there has not been a comprehensive assessment of factors that drive ecosystem changes throughout Alaska. Here we present research that improves our understanding of the main drivers of the spatiotemporal patterns of carbon dynamics using in situ observations, remote sensing data, and an array of modeling techniques. In the last 60 yr, Alaska has seen a large increase in mean annual air temperature (1.7°C), with the greatest warming occurring over winter and spring. Warming trends are projected to continue throughout the 21st century and will likely result in landscape-level changes to ecosystem structure and function. Wetlands, mainly bogs and fens, which are currently estimated to cover 12.5% of the landscape, strongly influence exchange of methane between Alaska's ecosystems and the atmosphere and are expected to be affected by thawing permafrost and shifts in hydrology. Simulations suggest the current proportion of near-surface (within 1 m) and deep (within 5 m) permafrost extent will be reduced by 9-74% and 33-55% by the end of the 21st century, respectively. Since 2000, an average of 678 595 ha/yr was burned, more than twice the annual average during 1950-1999. The largest increase in fire activity is projected for the boreal forest, which could result in a reduction in late-successional spruce forest (8-44%) and an increase in early-successional deciduous forest (25-113%) that would mediate future fire activity and weaken permafrost stability in the region. Climate warming will also affect vegetation communities across arctic regions, where the coverage of deciduous forest could increase (223-620%), shrub tundra may increase (4-21%), and graminoid tundra might decrease (10-24%). This study sheds light on the sensitivity of Alaska's ecosystems to change that has the potential to significantly affect local and regional carbon balance, but more research is needed to improve estimates of land-surface and subsurface properties, and to better account for ecosystem dynamics affected by a myriad of biophysical factors and interactions.
authors.affiliation: Stinger Ghaffarian Technologies (contractor to the U.S. Geological Survey), Sioux Falls, South Dakota, 57198, USA.|Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, 55108, USA.
authors.forename: Neal J
authors.initials: NJ
authors.lastname: Pastick
authors.affiliation: Neptune and Company, Lakewood, Colorado, 80215, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Duffy
authors.affiliation: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, USA.
authors.forename: Hélène
authors.initials: H
authors.lastname: Genet
authors.affiliation: International Arctic Research Center, Scenarios Network for Alaska and Arctic Planning, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, USA.
authors.forename: T Scott
authors.initials: TS
authors.lastname: Rupp
authors.affiliation: U.S. Geological Survey, Earth Resources Observation and Science Center, Sioux Falls, South Dakota, 57198, USA.
authors.forename: Bruce K
authors.initials: BK
authors.lastname: Wylie
authors.affiliation: Northern Research Station, U.S. Department of Agriculture Forest Service, Newtown Square, Pennsylvania, 19073, USA.
authors.forename: Kristofer D
authors.initials: KD
authors.lastname: Johnson
authors.affiliation: Alaska Ecoscience, Fairbanks, Alaska, 99709, USA.
authors.forename: M Torre
authors.initials: MT
authors.lastname: Jorgenson
authors.affiliation: ASRC Federal InuTeq (contractor to the U.S. Geological Survey), Sioux Falls, South Dakota, 57198, USA.
authors.forename: Norman
authors.initials: N
authors.lastname: Bliss
authors.affiliation: U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, USA.
authors.forename: A David
authors.initials: AD
authors.lastname: McGuire
authors.affiliation: Computational Earth Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA.
authors.forename: Elchin E
authors.initials: EE
authors.lastname: Jafarov
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, 55108, USA.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Knight
mesh_terms: D000413:Alaska; D057486:Carbon Cycle; D057965:Carbon Sequestration; D057231:Climate Change; D065946:Permafrost; D066188:Taiga; D013696:Temperature; D065929:Tundra
keywords: Alaska; boreal forest; carbon dynamics; climate change; permafrost; succession; surface water; tundra; wetlands; wildland fire