The impact of growing-season length variability on carbon assimilation and evapotranspiration over 88 years in the eastern US deciduous forest

M. A. White, S. W. Running, P. E. Thornton

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Abstract

Recent research suggests that increases in growing-season length (GSL) in mid-northern latitudes may be partially responsible for increased forest growth and carbon sequestration. We used the BIOME-BGC ecosystem model to investigate the impacts of including a dynamically regulated GSL on simulated carbon and water balance over a historical 88-year record (1900-1987) for 12 sites in the eastern USA deciduous broadleaf forest. For individual sites, the predicted GSL regularly varied by more than 15 days. When grouped into three climatic zones, GSL variability was still large and rapid. There is a recent trend in colder, northern sites toward a longer GSL, but not in moderate and warm climates. The results show that, for all sites, prediction of a long GSL versus using the mean GSL increased net ecosystem production (NEP), gross primary production (GPP), and evapotranspiration (ET); conversely a short GSL is predicted to decrease these parameters. On an absolute basis, differences in GPP between the dynamic and mean GSL simulations were larger than the differences in NEP. As a percentage difference, though, NEP was much more sensitive to changes in GSL than were either GPP or ET. On average, a 1-day change in GSL changed NEP by 1.6%, GPP by 0.5%, and ET by 0.2%. Predictions of NEP and GPP in cold climates were more sensitive to changes in GSL than were predictions in warm climates. ET was not similarly sensitive. First, our results strongly agree with field measurements showing a high correlation between NEP and dates of spring growth, and second they suggest that persistent increases in GSL may lead to long-term increases in carbon storage.

Original languageEnglish
Pages (from-to)139-145
Number of pages7
JournalInternational Journal of Biometeorology
Volume42
Issue number3
DOIs
StatePublished - Feb 1999

Funding

&p.2: wledgements We gratefully thank P.Y. Hughes, E.H. Mason, T.R. Karl, and W.A. Brower at the National Climatic Data Center for creating and extensively documenting the United States Historical Climatology Network Daily Temperature and Precipitation Data (http://cdiac.esd.ornl.gov/cdiac/ndps/ndp042.html). M.A. White is supported by the National Aeronautics and Space Administration Earth System Science fellowship program. This research was funded in part by National Aeronautics and Space Administration Moderate Resolution Imaging Spectrometer grant NAS5-31368.

FundersFunder number
National Aeronautics and Space AdministrationNAS5-31368

    Keywords

    • BIOME-BGC
    • Evapotranspiration
    • Gross ecosystem production
    • Growing season length
    • Net ecosystem production

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