title: Growing season and spatial variations of carbon fluxes of Arctic and boreal ecosystems in Alaska (USA).
abstract: To better understand the spatial and temporal dynamics of CO2 exchange between Arctic ecosystems and the atmosphere, we synthesized CO2 flux data, measured in eight Arctic tundra and five boreal ecosystems across Alaska (USA) and identified growing season and spatial variations of the fluxes and environmental controlling factors. For the period examined, all of the boreal and seven of the eight Arctic tundra ecosystems acted as CO2 sinks during the growing season. Seasonal patterns of the CO2 fluxes were mostly determined by air temperature, except ecosystem respiration (RE) of tundra. For the tundra ecosystems, the spatial variation of gross primary productivity (GPP) and net CO2 sink strength were explained by growing season length, whereas RE increased with growing degree days. For boreal ecosystems, the spatial variation of net CO2 sink strength was mostly determined by recovery of GPP from fire disturbance. Satellite-derived leaf area index (LAI) was a better index to explain the spatial variations of GPP and NEE of the ecosystems in Alaska than were the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). Multiple regression models using growing degree days, growing season length, and satellite-derived LAI explained much of the spatial variation in GPP and net CO2 exchange among the tundra and boreal ecosystems. The high sensitivity of the sink strength to growing season length indicated that the tundra ecosystem could increase CO2 sink strength under expected future warming, whereas ecosystem compositions associated with fire disturbance could play a major role in carbon release from boreal ecosystems.
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan. miyabi-flux@muh.biglobe.ne.jp
authors.forename: Masahito
authors.initials: M
authors.lastname: Ueyama
authors.affiliation: International Arctic Research Center, University of Alaska, Fairbanks, Alaska 99775, USA.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Iwata
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Harazono
authors.affiliation: Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775, USA.
authors.forename: Eugénie S
authors.initials: ES
authors.lastname: Euskirchen
authors.affiliation: Global Change Research Group, Department of Biology, San Diego State University, San Diego, California 92182, USA.
authors.forename: Walter C
authors.initials: WC
authors.lastname: Oechel
authors.affiliation: Global Change Research Group, Department of Biology, San Diego State University, San Diego, California 92182, USA.
authors.forename: Donatella
authors.initials: D
authors.lastname: Zona
mesh_terms: D000413:Alaska; D001110:Arctic Regions; D002244:Carbon / Q000737:chemistry* / Q000378:metabolism*; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism; D004784:Environmental Monitoring; D010944:Plants / Q000145:classification / Q000378:metabolism; D012621:Seasons; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D002244:Carbon