HR: 0800h
AN: C31A-1104    [Abstracts]
TI: Recent Increases in the Productivity of Alaskan Boreal Forest and Tundra: Evidence of an Acceleration of the Northern Terrestrial Carbon Cycle
AU: * Kimball, J S
EM: johnk@ntsg.umt.edu
AF: Flathead Lake Biological Station, The University of Montana 311 Biostation Lane, Polson, MT 59860-9659 United States
AU: * Kimball, J S
EM: johnk@ntsg.umt.edu
AF: Numerical Terradynamic Simulation Group, The University of Montana, Missoula, MT 59812 United States
AU: Zhao, M
EM: zhao@ntsg.umt.edu
AF: Numerical Terradynamic Simulation Group, The University of Montana, Missoula, MT 59812 United States
AU: Heinsch, F
EM: faithann@ntsg.umt.edu
AF: Numerical Terradynamic Simulation Group, The University of Montana, Missoula, MT 59812 United States
AU: McDonald, K C
EM: kyle.mcdonald@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 United States
AB: Northern ecosystems contain much of the global reservoir of terrestrial carbon that is potentially reactive in the context of near-term climate change. We assessed annual variability and recent trends in vegetation productivity for Alaska using a global production efficiency model driven by daily surface meteorology and satellite remote sensing of photosynthetic leaf area. We also conducted prognostic model simulations of the terrestrial carbon cycle to evaluate regional trends from the remote sensing record in the context of process-based simulations that more comprehensively represent the terrestrial carbon cycle. We find that a positive trend in annual vegetation productivity since the early 1980's is widespread and coincides with a summer warming trend of more than 1.8°C from 1982 to 2000. This positive productivity response is a direct result of the relaxation of cold temperature constraints to plant growth. Prognostic model simulations are generally consistent with the remote sensing record, and also indicate that an increase in soil decomposition and plant-available nitrogen with regional warming is partially responsible for the positive productivity response. The increase in productivity is also occurring at a greater rate than soil respiration, enhancing the near-term terrestrial sink strength for atmospheric CO₂. Despite an increasing trend in litter inputs to the soil organic carbon pool provided by a positive trend in vegetation productivity, we find evidence of a decline in less labile soil organic carbon, which represents approximately 75% of total carbon storage for the region. The regional carbon cycle also appears to be accelerating under a warming climate, with an increasing fraction of total carbon storage in vegetation biomass, leading to decreasing stability and more rapid turnover of the terrestrial carbon reservoir. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and at the University of Montana, Missoula, under contract to the National Aeronautics and Space Administration.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0480 Remote sensing
DE: 1640 Remote sensing (1855)
SC: Cryosphere [C]
MN: Fall Meeting 2005