The application and interpretation of Keeling plots in terrestrial carbon cycle research

Photosynthesis and respiration impart distinct isotopic signatures to the atmosphere that are used to constrain global carbon source/sink estimates and partition ecosystem fluxes. Increasingly, the “Keeling plot” method is being used to determine the carbon isotope composition of ecosystem respiration (δ13CR) in order to better understand the processes controlling ecosystem isotope discrimination. In this paper we synthesize emergent patterns in δ13CR by analyzing 146 Keeling plots constructed at 33 sites across North and South America. In order to interpret results from disparate studies, we discuss the assumptions underlying the Keeling plot method and recommend standardized methods for determining δ13CR. These include the use of regression calculations that account for error in the x variable, and constraining estimates of δ13CR to nighttime periods. We then recalculate δ13CR uniformly for all sites. We found a high degree of temporal and spatial variability in C3 ecosystems, with individual observations ranging from −19.0 to −32.6‰. Mean C3 ecosystem discrimination was 18.3‰. Precipitation was a major driver of both temporal and spatial variability of δ13CR, suggesting (1) a large influence of recently fixed carbon on ecosystem respiration and (2) a significant effect of previous climatic effects on δ13CR. These results illustrate the importance of water availability as a key control on atmospheric 13CO2 and highlight the potential of δ13CR as a useful tool for integrating environmental effects on dynamic canopy and ecosystem processes.

[1]  G. Farquhar,et al.  13C discrimination during CO2 assimilation by the terrestrial biosphere , 1994, Oecologia.

[2]  C. Körner,et al.  Carbon isotope discrimination by plants follows latitudinal and altitudinal trends , 1991, Oecologia.

[3]  J. Kaplan,et al.  The stable carbon isotope composition of the terrestrial biosphere: Modeling at scales from the leaf to the globe , 2002 .

[4]  J. Ehleringer,et al.  Carbon isotope discrimination in forest and pasture ecosystems of the Amazon Basin, Brazil , 2002 .

[5]  Nina Buchmann,et al.  Predicting daytime carbon isotope ratios of atmospheric CO2 within forest canopies , 2002 .

[6]  J. Ehleringer,et al.  Age-related variations in delta(13)C of ecosystem respiration across a coniferous forest chronosequence in the Pacific Northwest. , 2002, Tree physiology.

[7]  N. McDowell,et al.  13C content of ecosystem respiration is linked to precipitation and vapor pressure deficit , 2002, Oecologia.

[8]  Sandy P. Harrison,et al.  Global Biogeochemical Cycles in the Climate System , 2001 .

[9]  N. Buchmann,et al.  Large-scale forest girdling shows that current photosynthesis drives soil respiration , 2001, Nature.

[10]  A. Arneth,et al.  Vertical profiles, boundary layer budgets, and regional flux estimates for CO2 and its 13C/12C ratio and for water vapor above a forest/bog mosaic in central Siberia , 2001 .

[11]  F. Badeck,et al.  δ13C of CO2 respired in the dark in relation to δ13C of leaf metabolites: comparison between Nicotiana sylvestris and Helianthus annuus under drought , 2001 .

[12]  R. Monson,et al.  Partitioning net ecosystem carbon exchange with isotopic fluxes of CO2 , 2001 .

[13]  J. Kaplan,et al.  Carbon isotope discrimination of terrestrial ecosystems - how well do observed and modeled results match? , 2001 .

[14]  Corinne Le Quéré,et al.  Regional changes in carbon dioxide fluxes of land and oceans since 1980. , 2000, Science.

[15]  Nina Buchmann,et al.  Biotic and abiotic factors controlling soil respiration rates in Picea abies stands , 2000 .

[16]  M. Henn,et al.  Differential C Isotope Discrimination by Fungi during Decomposition of C3- and C4-Derived Sucrose , 2000, Applied and Environmental Microbiology.

[17]  K. Wilson,et al.  A spectral analysis of biosphere-atmosphere trace gas flux densities and meteorological variables across hour to multi-year time scales , 2000 .

[18]  L. Sternberg,et al.  The use of stable isotopes to study ecosystem gas exchange , 2000, Oecologia.

[19]  Susan E. Trumbore,et al.  AGE OF SOIL ORGANIC MATTER AND SOIL RESPIRATION: RADIOCARBON CONSTRAINTS ON BELOWGROUND C DYNAMICS , 2000 .

[20]  J. Ehleringer,et al.  Carbon isotope ratios in belowground carbon cycle processes , 2000 .

[21]  P. Tans,et al.  Global Carbon Sinks and Their Variability Inferred from Atmospheric O2 and δ13C , 2000 .

[22]  C. Somerville.  Department of plant biology , 2000 .

[23]  D. Baldocchi,et al.  Dynamics of isotopic exchange of carbon dioxide in a Tennessee deciduous forest , 1999 .

[24]  P. Rochette,et al.  Separating Soil Respiration into Plant and Soil Components Using Analyses of the Natural Abundance of Carbon‐13 , 1999 .

[25]  Schweizer,et al.  Isotopic ((13)C) fractionation during plant residue decomposition and its implications for soil organic matter studies. , 1999, Rapid communications in mass spectrometry : RCM.

[26]  P. Ciais,et al.  A global calculation of the δ13C of soil respired carbon: Implications for the biospheric uptake of anthropogenic CO2 , 1999 .

[27]  D. Baldocchi,et al.  The carbon balance of tropical, temperate and boreal forests , 1999 .

[28]  D. Baldocchi,et al.  Below-canopy and soil CO2 fluxes in a ponderosa pine forest , 1999 .

[29]  F. Badeck,et al.  δ13C of CO2 respired in the dark in relation to δ13C of leaf carbohydrates in Phaseolus vulgaris L. under progressive drought , 1999 .

[30]  J. Ehleringer,et al.  Spatial and temporal variation in the carbon and oxygen stable isotope ratio of respired CO2 in a boreal forest ecosystem , 1999 .

[31]  H. Griffiths,et al.  Determinants of isotopic coupling of CO2 and water vapour within a Quercus petraea forest canopy , 1999, Oecologia.

[32]  J. Ehleringer,et al.  Elevated CO2 and temperature impacts on different components of soil CO2 efflux in Douglas‐fir terracosms , 1999 .

[33]  P. Bakwin,et al.  Determination of the isotopic(13C/12C) discrimination by terrestrial biology from a global network of observations , 1998 .

[34]  J. Ehleringer,et al.  Carbon and oxygen isotope ratios of ecosystem respiration along an Oregon conifer transect: preliminary observations based on small-flask sampling. , 1998, Tree physiology.

[35]  J. Ehleringer,et al.  Carbon isotope dynamics in Abies amabilis stands in the Cascades , 1998 .

[36]  P. Tans.  Oxygen isotopic equilibrium between carbon dioxide and water in soils , 1998 .

[37]  Dennis D. Baldocchi,et al.  On using eco-physiological, micrometeorological and biogeochemical theory to evaluate carbon dioxide, water vapor and trace gas fluxes over vegetation: a perspective , 1998 .

[38]  J. Ehleringer,et al.  Carbon isotope discrimination of terrestrial ecosystems , 1998 .

[39]  J. Ehleringer,et al.  Ecosystem-atmosphere CO(2) exchange: interpreting signals of change using stable isotope ratios. , 1998, Trends in ecology & evolution.

[40]  G. Campbell,et al.  Water Flow in Soil , 1998 .

[41]  G. Gleixner,et al.  Carbon isotope effects on key reactions in plant metabolism and 13C-patterns in natural compounds , 1998 .

[42]  J. Ehleringer,et al.  CO2 concentration profiles, and carbon and oxygen isotopes in C3, and C4 crop canopies , 1998 .

[43]  D. Nepstad,et al.  Carbon dioxide recycling in two Amazonian tropical forests , 1997 .

[44]  J. Ehleringer,et al.  Photosynthesis and carbon isotope discrimination in boreal forest ecosystems: A comparison of functional characteristics in plants from three mature forest types , 1997 .

[45]  J. Randerson,et al.  Carbon 13 exchanges between the atmosphere and biosphere , 1997 .

[46]  Luiz Antonio Martinelli,et al.  Contribution of transpiration to forest ambient vapour based on isotopic measurements , 1997 .

[47]  J. Ehleringer,et al.  Carbon Isotopic Fractionation Does Not Occur during Dark Respiration in C3 and C4 Plants , 1997, Plant physiology.

[48]  M. G. Ryan,et al.  Hydraulic Limits to Tree Height and Tree Growth , 1997 .

[49]  J. Ehleringer,et al.  Carbon isotope composition of boreal plants: functional grouping of life forms , 1997, Oecologia.

[50]  J. Ehleringer,et al.  Interseasonal comparison of CO2 concentrations, isotopic composition, and carbon dynamics in an Amazonian rainforest (French Guiana) , 1997, Oecologia.

[51]  J. Ehleringer,et al.  Influence of stand structure on carbon-13 of vegetation, soils, and canopy air within deciduous and evergreen forests in Utah, United States , 1997, Oecologia.

[52]  P. Rochette,et al.  Quantifying rhizosphere respiration in a corn crop under field conditions , 1997 .

[53]  T. Machida,et al.  Aircraft measurements of the concentrations of CO2, CH4, N2O, and CO and the carbon and oxygen isotopic ratios of CO2 in the troposphere over Russia , 1997 .

[54]  L. Flanagan,et al.  Leaf δ13C in Pinus resinosa trees and understory plants: variation associated with light and CO2 gradients , 1997, Oecologia.

[55]  J. Ehleringer,et al.  Carbon isotope discrimination during photosynthesis and the isotope ratio of respired CO2 in boreal forest ecosystems , 1996 .

[56]  Steven W. Running,et al.  Strategies for measuring and modelling carbon dioxide and water vapour fluxes over terrestrial ecosystems , 1996 .

[57]  J. William Munger,et al.  Measurements of carbon sequestration by long‐term eddy covariance: methods and a critical evaluation of accuracy , 1996 .

[58]  D. Yakir,et al.  Fluxes of CO2 and water between terrestrial vegetation and the atmosphere estimated from isotope measurements , 1996, Nature.

[59]  T. Boutton,et al.  Stable carbon isotope ratios of soil organic matter and their use as indicators of vegetation and climate change. , 1996 .

[60]  D. Hollinger,et al.  Vegetation Effects on the Isotopic Composition of Atmospheric CO2 at Local and Regional Scales: Theoretical Aspects and a Comparison Between Rain Forest in Amazonia and a Boreal Forest in Siberia , 1996 .

[61]  P. Bakwin,et al.  Measurements of carbon dioxide on a very tall tower , 1995 .

[62]  Charles D. Bonham,et al.  Least squares regression vs. geometric mean regression for ecotoxicology studies , 1995 .

[63]  P. Ciais,et al.  A Large Northern Hemisphere Terrestrial CO2 Sink Indicated by the 13C/12C Ratio of Atmospheric CO2 , 1995, Science.

[64]  P. P. Tans,et al.  Changes in oceanic and terrestrial carbon uptake since 1982 , 1995, Nature.

[65]  Pieter P. Tans,et al.  Oceanic 13C/12C observations: A new window on ocean CO2 uptake , 1993 .

[66]  H. Griffiths,et al.  Carbon Isotope Discrimination and the Coupling of CO2 Fluxes within Forest Canopies , 1993 .

[67]  Martina Schmidt,et al.  The regional budget of atmospheric methane of a highly populated area , 1993 .

[68]  Graham D. Farquhar,et al.  Stable isotopes and plant carbon-water relations. , 1993 .

[69]  William H. Press,et al.  The Art of Scientific Computing Second Edition , 1998 .

[70]  B. Tilbrook,et al.  Oceanic Uptake of Fossil Fuel CO2: Carbon-13 Evidence , 1992, Science.

[71]  S. Daniels-McQueen,et al.  Derepression of ferritin messenger RNA translation by hemin in vitro. , 1990, Science.

[72]  S. Wofsy,et al.  13C/12C of atmospheric CO2 in the Amazon Basin: Forest and river sources , 1989 .

[73]  S. Mulkey,et al.  Ecological Interpretation of Leaf Carbon Isotope Ratios: Influence of Respired Carbon Dioxide , 1989 .

[74]  D. H. Peterson,et al.  Aspects of climate variability in the Pacific and the western Americas , 1989 .

[75]  William H. Press,et al.  Book-Review - Numerical Recipes in Pascal - the Art of Scientific Computing , 1989 .

[76]  J. Ehleringer,et al.  Carbon Isotope Discrimination and Photosynthesis , 1989 .

[77]  R. Hodson,et al.  Depletion of 13C in lignin and its implications for stable carbon isotope studies , 1987, Nature.

[78]  H. Friedli,et al.  Measurements of concentration, 13C/12C and 18O/16O ratios of tropospheric carbon dioxide over Switzerland , 1987 .

[79]  H. Oeschger,et al.  Measurements of concentration, 13 C/ 12 C and 18 O/ 16 O ratios of tropospheric carbon dioxide over Switzerland , 1987 .

[80]  William H. Press,et al.  Numerical recipes in C. The art of scientific computing , 1987 .

[81]  R. Francey.  Cape Grim isotope measurements — A preliminary assessment , 1985 .

[82]  G. Farquhar,et al.  Isotopic Composition of Plant Carbon Correlates With Water-Use Efficiency of Wheat Genotypes , 1984 .

[83]  R. Guy,et al.  Stable carbon isotope ratios of flooded and nonflooded sunflowers (Helianthus annuus) , 1984 .

[84]  T. Sharkey,et al.  Stomatal conductance and photosynthesis , 1982 .

[85]  A. Ehrenberg.  Environmental biophysics. , 1977, Acta biochimica et biophysica; Academiae Scientiarum Hungaricae.

[86]  W. Ricker.  Linear Regressions in Fishery Research , 1973 .

[87]  Charles D. Keeling,et al.  The concentration and isotopic abundances of carbon dioxide in rural and marine air , 1961 .

[88]  Charles D. Keeling,et al.  The concentration and isotopic abundances of atmospheric carbon dioxide in rural areas , 1958 .

[89]  N. McDowell,et al.  Ehleringer 13 C content of ecosystem respiration is linked to precipitation and vapor pressure deficit , 2022 .