The Phenology of Gross Ecosystem Productivity and Ecosystem Respiration in Temperate Hardwood and Conifer Chronosequences

  • Asko Noormets
  • Jiquan Chen
  • Lianhong Gu
  • Ankur Desai


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. The length of the active season (ASL) varied more due to differences in the timing of the end rather than the start of the active period. ASL of GEP was consistently greater in conifers than hardwoods, but the opposite was true for ER.


Normalize Difference Vegetation Index Ecosystem Respiration Enhance Vegetation Index Young Stand Mature Stand 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations Phenological stages and dates


length of active season (days)


length of active season (days)


length of active season (days)


end of active season (DOY)


day of half-maximum flux (DOY)


length of flux development period (days)


length of flux recession period (days)


length of peak flux period (days)


rate of development (g C m−2 d−1)


rate of recession (g C m−2 d−1)


start of active season (DOY) Subscripts appended to any of the above


index or date referring to gross ecosystem productivity


index or date referring to ecosystem respiration Site abbreviations


intermediate hardwood, 2003


intermediate red pine, 2003


mature hardwood, 2002


mature hardwood, 2003


mature red pine, 2002


mature red pine, 2003


young hardwood, 2002


young red pine, 2002



This work was supported by USDA Forest Service Southern Global Change Program (AN, JC) and National Science Foundation (JC). We thank Ben Bond-Lamberty, Eero Nikinmaa and Andrew Richardson for constructive comments.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Asko Noormets
    • 1
  • Jiquan Chen
    • 2
  • Lianhong Gu
    • 3
  • Ankur Desai
    • 4
  1. 1.Department of Forestry and Environmental ResourcesNorth Carolina State UniversityRaleighUSA
  2. 2.Department of Environmental SciencesUniversity of ToledoToledoUSA
  3. 3.Environmental Sciences DivisionOak Ridge National LaboratoryOak RidgeUSA
  4. 4.A. DesaiDepartment of Atmospheric and Oceanic SciencesUniversity of Wisconsin-MadisonMadisonUSA

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