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    Author(s): A. Noormets
    Date: 2009
    Source: In: Noormets, A., ed. Phenology of ecosystem processes. Springer: New York, NY. 57-82.
    Publication Series: Book
    Station: Southern Research Station
    PDF: View PDF  (470.15 KB)


    The relative duration of active and dormant seasons has a strong influence on ecosystem net carbon balance and its carbon uptake potential. While recognized as an important source of temporal and spatial variability, the seasonality of ecosystem carbon balance has not been studied explicitly, and still lacks standard terminology. In the current chapter, we apply a curve fitting procedure to define seasonal transitions in ecosystem gross productivity (GEP) and respiration (ER), and we show that the temporal changes in these two fluxes are not synchronous, and that the transition dates and rates of change vary both across sites and between years. Carbon uptake period (CUP), a common phenological metric, defined from ecosystem net carbon exchange (NEE), is related to these periods of activity, but the differential sensitivities of GEP and ER to environmental factors complicate the interpretation of variation in CUP alone. On a landscape scale, differences in stand age represent a major source of heterogeneity reflected in different flux capacities as well as microclimate. In the current study, we evaluate age-related differences in the phenological transitions of GEP and ER using hardwood and conifer chronosequences. While a significant portion of variability in GEP seasonality was explained with stand age, the influence of interannual climatic variability exceeded these, and was the predominant factor affecting ER seasonality.

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    Noormets, A.; Chen, J.; Gu, L.; Desai, A. 2009. The phenology of gross ecosystem productivity and ecosystem respiration in temperate hardwood and conifer chronosequences. In: Noormets, A., ed. Phenology of ecosystem processes. Springer: New York, NY. 57-82.

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