Abstract
Net ecosystem exchange (NEE) represents the difference between carbon assimilated through photosynthesis, or gross primary productivity (GPP), and carbon released via ecosystem respiration (ER). NEE, measured via eddy covariance and chamber techniques, must be partitioned into these fluxes to accurately describe and understand the carbon dynamics of an ecosystem. GPP and daytime ER may be significantly overestimated if the light inhibition of foliar mitochondrial respiration, or “Kok effect,” is not accurately estimated and further integrated into ecosystem measurements. The light inhibition of respiration, a composite effect of multiple cellular pathways, is reported to cause between 25‐100% inhibition of foliar mitochondrial respiration, and for this reason needs to be considered when estimating larger carbon fluxes. Partitioning of respiration between autotrophic and heterotrophic respiration, and applying these scaled respiratory fluxes to the ecosystem‐level proves to be difficult, and the integration of light inhibition into single and continuous measures of ecosystem respiration will require new interpretations and analysis of carbon exchange in terrestrial ecosystems.
Highlights
The flow of carbon between the land and atmosphere accounts for immense fluxes of carbon dioxide globally
Net ecosystem exchange (NEE), the difference between the carbon acquired through photosynthetic fixation and the carbon released through Ecosystem respiration (ER), can be measured through eddy covariance techniques (Baldocchi et al 1988)
Neglecting to include the light inhibition of respiration can lead to overestimations of both gross primary productivity (GPP) and ER (Amthor and Baldocchi 2001, Janssens et al 2001, Morgenstern et al 2004, Wohlfahrt et al 2005b, Bruhn et al 2011); as GPP is derived from ER, inaccurate assessments of ER will confound GPP
Summary
The flow of carbon between the land and atmosphere accounts for immense fluxes of carbon dioxide globally. Net ecosystem exchange (NEE), the difference between the carbon acquired through photosynthetic fixation (gross primary productivity, GPP) and the carbon released through ER, can be measured through eddy covariance techniques (Baldocchi et al 1988). While these methods allow for estimation of ecosystem scale CO2 flux, partitioning and interpretation of this value is difficult and requires the consideration of multiple scales and environmentally sensitive processes (Chambers et al 2004, Griffis et al 2004, Gilmanov et al 2007, Zobitz et al 2008, Lasslop et al 2010). Our paper addresses the measurement and partitioning of NEE into different fluxes of carbon dioxide, and suggests how RL should be evaluated and incorporated into models of ecosystem carbon cycling
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