Journal ArticleDOI
Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future
TLDR
The eddy covariance method is most accurate when the atmospheric conditions (wind, temperature, humidity, CO2) are steady, the underlying vegetation is homogeneous and it is situated on flat terrain for an extended distance upwind as discussed by the authors.Abstract:
The eddy covariance technique ascertains the exchange rate of CO2 across the interface between the atmosphere and a plant canopy by measuring the covariance between fluctuations in vertical wind velocity and CO2 mixing ratio. Two decades ago, the method was employed to study CO2 exchange of agricultural crops under ideal conditions during short field campaigns. During the past decade the eddy covariance method has emerged as an important tool for evaluating fluxes of carbon dioxide between terrestrial ecosystems and the atmosphere over the course of a year, and more. At present, the method is being applied in a nearly continuous mode to study carbon dioxide and water vapor exchange at over a hundred and eighty field sites, worldwide. The objective of this review is to assess the eddy covariance method as it is being applied by the global change community on increasingly longer time scales and over less than ideal surfaces.
The eddy covariance method is most accurate when the atmospheric conditions (wind, temperature, humidity, CO2) are steady, the underlying vegetation is homogeneous and it is situated on flat terrain for an extended distance upwind. When the eddy covariance method is applied over natural and complex landscapes or during atmospheric conditions that vary with time, the quantification of CO2 exchange between the biosphere and atmosphere must include measurements of atmospheric storage, flux divergence and advection.
Averaging CO2 flux measurements over long periods (days to year) reduces random sampling error to relatively small values. Unfortunately, data gaps are inevitable when constructing long data records. Data gaps are generally filled with values produced from statistical and empirical models to produce daily and annual sums of CO2 exchange. Filling data gaps with empirical estimates do not introduce significant bias errors because the empirical algorithms are derived from large statistical populations. On the other hand, flux measurement errors can be biased at night when winds are light and intermittent. Nighttime bias errors tend to produce an underestimate in the measurement of ecosystem respiration.
Despite the sources of errors associated with long-term eddy flux measurements, many investigators are producing defensible estimates of annual carbon exchange. When measurements come from nearly ideal sites the error bound on the net annual exchange of CO2 is less than ±50 g C m−2 yr−1. Additional confidence in long-term measurements is growing because investigators are producing values of net ecosystem productivity that are converging with independent values produced by measuring changes in biomass and soil carbon, as long as the biomass inventory studies are conducted over multiple years.read more
Citations
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Journal ArticleDOI
Shifting plant phenology in response to global change
TL;DR: Recent advances in several fields that have enabled scaling between species responses to recent climatic changes and shifts in ecosystem productivity are discussed, with implications for global carbon cycling.
Journal ArticleDOI
‘Breathing’ of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems
TL;DR: Key findings reported include: ecosystems with the greatest net carbon uptake have the longest growing season, not the greatest FA; many old-growth forests act as carbon sinks; and year-to-year decreases in FN are attributed to a suite of stresses that decrease FA and FR in tandem.
Journal ArticleDOI
Sources of CO2 efflux from soil and review of partitioning methods
TL;DR: In this article, the root-derived CO2 efflux from soil has been distinguished and described according to their turnover rates and the mean residence time of carbon in the soil according to five main biogenic sources.
Journal ArticleDOI
Reconciling carbon-cycle concepts, terminology, and methods
F. S. Chapin,George M. Woodwell,James T. Randerson,Edward B. Rastetter,Gary M. Lovett,Dennis D. Baldocchi,Deborah A. Clark,Mark E. Harmon,David S. Schimel,Riccardo Valentini,Christian Wirth,John D. Aber,Jonathan J. Cole,Michael L. Goulden,Jennifer W. Harden,Martin Heimann,Robert W. Howarth,Pamela A. Matson,A. D. McGuire,Jerry M. Melillo,Harold A. Mooney,Jason C. Neff,Richard A. Houghton,Michael L. Pace,Michael G. Ryan,Steven W. Running,Osvaldo E. Sala,William H. Schlesinger,Ernst Detlef Schulze +28 more
TL;DR: In this article, the imbalance between gross primary production (GPP) and ecosystem respiration (ER) was defined as a measure of the amount of carbon being transferred from one ecosystem to another.
Journal ArticleDOI
CO2 balance of boreal, temperate, and tropical forests derived from a global database
Sebastiaan Luyssaert,Sebastiaan Luyssaert,I. Inglima,Martin Jung,Andrew D. Richardson,Markus Reichstein,Dario Papale,S. L. Piao,Ernst Detlef Schulze,Lisa Wingate,Giorgio Matteucci,Luiz E. O. C. Aragão,Marc Aubinet,Christian Beer,Christian Bernhofer,Kevin Black,Damien Bonal,Jean-Marc Bonnefond,Jeffrey Q. Chambers,Philippe Ciais,Bruce D. Cook,Kenneth J. Davis,A. J. Dolman,Birgit Gielen,Michael L. Goulden,John Grace,A. Granier,Achim Grelle,Timothy J. Griffis,Thomas Grünwald,Gabriele Guidolotti,Paul J. Hanson,Richard Harding,David Y. Hollinger,Lucy R. Hutyra,Pasi Kolari,Bart Kruijt,Werner L. Kutsch,Fredrik Lagergren,T. Laurila,Beverly E. Law,G. Le Maire,Anders Lindroth,Denis Loustau,Yadvinder Malhi,J. Mateus,Mirco Migliavacca,Laurent Misson,Leonardo Montagnani,John Moncrieff,Eddy Moors,J. W. Munger,Eero Nikinmaa,Scott V. Ollinger,Gabriel Pita,Corinna Rebmann,Olivier Roupsard,Nobuko Saigusa,María José Sanz,Guenther Seufert,Carlos A. Sierra,Marie-Louise Smith,Jianwu Tang,Riccardo Valentini,Timo Vesala,Ivan A. Janssens +65 more
TL;DR: In this article, the authors present a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g., leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics.
References
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Journal ArticleDOI
Correction of flux measurements for density effects due to heat and water vapour transfer
TL;DR: In this article, the basic relationships are discussed in the context of vertical transfer in the lower atmosphere, and the required corrections to the measured flux are derived, where the correction to measurements of water vapour flux will often be only a few per cent but will sometimes exceed 10 percent.
Journal ArticleDOI
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
Dennis D. Baldocchi,Eva Falge,Lianhong Gu,Richard J. Olson,David Y. Hollinger,Steven W. Running,P. M. Anthoni,Ch. Bernhofer,Kenneth J. Davis,Robert G. Evans,Jose D. Fuentes,Allen H. Goldstein,Gabriel G. Katul,Beverly E. Law,Xuhui Lee,Yadvinder Malhi,Tilden P. Meyers,William Munger,Walter C. Oechel,Kim Pilegaard,Hans Peter Schmid,Riccardo Valentini,Shashi B. Verma,Timo Vesala,Kell B. Wilson,S. C. Wofsy +25 more
TL;DR: The FLUXNET project as mentioned in this paper is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere.
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
Dennis D. Baldocchi,Eva Falge,Lianhong Gu,Richard J. Olson,David Y. Hollinger,Steven W. Running,P. M. Anthoni,Christian Bernhofer,Kenneth J. Davis,Robert G. Evans +9 more
Journal ArticleDOI
Energy balance closure at FLUXNET sites
Kell B. Wilson,Allen H. Goldstein,Eva Falge,Marc Aubinet,Dennis D. Baldocchi,Paul Berbigier,Christian Bernhofer,Reinhart Ceulemans,Han Dolman,Christopher B. Field,Achim Grelle,A. Ibrom,Beverly E. Law,Andrew S. Kowalski,Tilden P. Meyers,John Moncrieff,Russell K. Monson,Walter C. Oechel,John Tenhunen,Riccardo Valentini,Shashi B. Verma +20 more
TL;DR: A comprehensive evaluation of energy balance closure is performed across 22 sites and 50 site-years in FLUXNET, a network of eddy covariance sites measuring long-term carbon and energy fluxes in contrasting ecosystems and climates as mentioned in this paper.
Journal ArticleDOI
Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer
TL;DR: In this article, a system of models for the simulation of gas and energy exchange of a leaf of a C3 plant in free air is presented, where the physiological processes are simulated by sub-models that: (a) give net photosynthesis (An) as a function of environmental and leaf parameters and stomatal conductance (gs); (b) give g, as well as the concentration of CO2 and H2O in air at the leaf surface and the current rate of photosynthesis of the leaf.
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