A Database of Herbaceous Vegetation Responses to Elevated Atmospheric CO₂ (NDP-073)

Data PDF file

Contributed by
Michael H. Jones
Peter S. Curtis
Department of Evolution, Ecology, and Organismal Biology
The Ohio State University
Columbus, Ohio

Prepared by Robert M. Cushman and Antoinette L. Brenkert
Carbon Dioxide Information Analysis Center
Environmental Sciences Division
Publication No. 4909
Date Published: November 1999

Prepared for the
Environmental Sciences Division
Office of Biological and Environmental Research
Budget Activity Number KP 12 04 01 0

Prepared by the
Carbon Dioxide Information Analysis Center
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831-6290
managed by
LOCKHEED MARTIN ENERGY RESEARCH CORP.
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-96OR22464

Abstract
1. Background Information
2. Applications of the Data
3. Data Limitations and Restrictions
4. Data Checks and Processing Performed by CDIAC
5. Instructions for Obtaining the Data and Documentation
6. References
7. Listing of Files Provided
8. Description of the Documentation File
9. Description, Format, and Partial Listings of the ASCII Data Files
10. Description and Format of the Lotus 1-2-3 Binary Spreadsheet Files
11. SAS and Fortran Codes to Access the Data
Appendix A: Species Included in Database
Appendix B: Full Listing of Refs.dat
Appendix C: Full Listing of Comments.dat

Abstract

Jones, M. H., P. S. Curtis, R. M. Cushman, and A. L. Brenkert. 1999. A Database of Herbaceous Vegetation Responses to Elevated Atmospheric CO₂. ORNL/CDIAC-124, NDP-073. Carbon Dioxide Information Analysis Center, U.S. Department of Energy, Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.

To perform a statistically rigorous meta-analysis of research results on the response by herbaceous vegetation to increased atmospheric CO₂ levels, a multiparameter database of responses was compiled from the published literature. Seventy-eight independent CO₂-enrichment studies, covering 53 species and 26 response parameters, reported mean response, sample size, and variance of the response (either as standard deviation or standard error). An additional 43 studies, covering 25 species and 6 response parameters, did not report variances. This numeric data package accompanies the Carbon Dioxide Information Analysis Center's (CDIAC's) NDP- 072, which provides similar information for woody vegetation.

This numeric data package contains a 30-field data set of CO₂- exposure experiment responses by herbaceous plants (as both a flat ASCII file and a spreadsheet file), files listing the references to the CO₂-exposure experiments and specific comments relevant to the data in the data sets, and this documentation file (which includes SAS and Fortran codes to read the ASCII data file; SAS is a registered trademark of the SAS Institute, Inc., Cary, North Carolina 27511).

The data files and this documentation are available without charge on a variety of media and via the Internet from CDIAC.

Keywords: carbon dioxide, meta-analysis, vegetation

1. Background Information

To perform a statistically rigorous synthesis of research results on the response by vegetation to increased atmospheric CO₂ levels, a multiparameter database of herbaceous-plant responses was compiled from the published literature (Wand et al. 1999; Jones et al. submitted). Seventy-eight independent CO₂-enrichment studies, covering 53 species and 26 response parameters, reported mean response, sample size, and variance of the response. An additional 43 studies, covering 25 species and six response parameters, did not report variances. The plant species included in the database are listed in Appendix A. Meta-analytical methods (Cooper and Hedges 1994; Gurevitch and Hedges 1993; Gurevitch et al. 1992) have been applied to part of this database (Wand et al. 1999). This numeric data package accompanies the Carbon Dioxide Information Analysis Center's (CDIAC's) NDP- 072 (Curtis et al. 1999), which provides similar information for woody vegetation.

Physiological "acclimation" or "downward regulation" of photosynthetic rates, stomatal conductance, dark respiration, and water-use efficiency of plants exposed to elevated CO₂ levels can be analyzed according to the following definitions. "Acclimation" is in general defined as "diminishing enhancement of photosynthesis by elevated CO₂ with time" (Mousseau and Saugier 1992). "Downward regulation" can be defined as "the initial stimulation of enhanced photosynthesis and growth by atmospheric enrichment eroding with time" (Idso and Kimball 1992). The phenomenon is also called "downward acclimation": "following prolonged exposure to high CO₂, photosynthetic capacity measured at either elevated or ambient CO₂ partial pressure falls to below that of plants exposed only to ambient CO₂" (Curtis and Teeri 1992).

Data were compiled for the database according to the following guidelines. The durations of experimental exposures are always reported. When more than one elevated- CO₂ treatment level is reported, only the level that is approximately twice the ambient level is included. For photosynthetic rates, stomatal conductance, dark respiration, and water use efficiency, only final- exposure experiment results are included; multiple measurements over time for the same plant are not. For acclimatory responses, only data for (1) plants grown at ambient CO₂ levels and measured at elevated CO₂ levels and (2) plants grown at elevated CO₂ levels and measured at elevated CO₂ levels are included.

2. Applications of the Data

This database was produced to support a meta-analysis of the effects of elevated CO₂ on herbaceous vegetation (Wand et al. 1999), and it was formatted accordingly. For other applications, the user should be aware that the data may be reported in more than one unit for a given variable (e.g., aboveground weight is reported in units of grams, grams per square meter, grams per plant, grams per pot, kilograms per hectare, kilograms per square meter, milligrams, milligrams per plant, and tons per hectare); this is not a problem for meta- analysis, but for other applications the user may need to convert the data to consistent units. The effects of environmental factors (e.g., nutrient levels, light intensity, temperature), stress treatments (e.g., drought, heat, ozone), and the effects of experimental conditions (e.g., duration of CO₂ exposure, pot size, type of CO₂ exposure facility) on plant responses to elevated CO₂ levels can be explored with this database.

3. Data Limitations and Restrictions

In many papers, the data were reported graphically rather than numerically. In such cases, values reported in the database were digitized from the printed figures and may therefore be less accurate.

Some of the standard deviations (and derived standard errors and coefficients of variation) in this database may be incorrect. When a "standard deviation" was reported in a published paper, it was not generally possible to verify whether this value was a sample standard deviation or the standard deviation of the mean, which is sometimes used synonymously with standard error (i.e., standard error of the mean). Unfortunately, it was not possible to settle this issue definitively without personally contacting the authors of the published papers. In all cases, where not specified or known to be otherwise, a reported standard deviation was taken to be the sample standard deviation. If this assumption was in error, then the standard deviation, standard error, and coefficient of variation reported in this database would be incorrect.

In some cases an error bar in a figure or confidence interval in a table was not specified as standard deviation or standard error. If it was not possible to determine whether the reported variability was standard deviation or standard error, a missing-value indicator (-9.99) is entered under standard deviation and standard error for that observation.

In some cases (e.g., in long-term exposures), the duration of CO₂ exposure was approximated.

As noted in Sect. 2, various units may be used for the same parameter, so the user should apply caution in integrating observations from more than one paper. Units are reported in the database.

4. Data Checks and Processing Performed By CDIAC

An important part of the data-packaging process at CDIAC involves the quality assurance (QA) of data before distribution. To guarantee data of the highest possible quality, CDIAC performs extensive QA checks, examining the data for completeness, reasonableness, and accuracy, through close cooperation with the data contributor.

All entries in the data file were visually inspected for reasonableness, and selected entries were spot-checked against the original publications.

The following paragraphs describe the additional data checks that were performed in the preparation of this numeric data package and the resulting revisions to the database.

Excel (a registered trademark of the Microsoft Corporation, Redmond, Washington 98052) was used to convert the spreadsheets provided by the principal investigators to Lotus 1-2- 3 (a registered trademark of the Lotus Development Corporation, Cambridge, Massachusetts 02142) format. Two separate databases, one including observations for which standard deviation or standard error was reported ("weighted") and the other consisting of observations without reported standard deviation or standard error ("unweighted"), were merged into one.

Lists of entries for each field were generated to identify possible spelling variants, typographical errors, or order-of-magnitude errors in the original literature or in the compilation and data entry of the database.

Where a cited paper reported standard error, standard deviation was calculated and tabulated (such occurrences are indicated in the database with a SDC flag-code).

The ratio of elevated/ambient for X, SE, SD, and N was calculated for all parameters and all observations; then all observations were ranked on the basis of each ratio, whenever possible (all these variables were not present for all observations), to identify suspect values (defined as jumps of greater than twofold between adjacent observations). The ranked ratios of X_ELEV/X_AMB ranged without abrupt jumps from 0.19 to 3.5, except for the ratio for variable AGWT reported from PAP_NO 2440 (X_ELEV/X_AMB = 9.2); the individual values for X_ELEV and X_AMB were verified in that publication (they were digitized from Fig. 5). The ranked ratios of SE_ELEV/SE_AMB and SD_ELEV/SD_AMB ranged without abrupt jumps from 0.05 to 18, except for the ratios of 0 for variables TOTWT, RGR, PN, and GS reported from PAP_NO 2363; the individual values for which standard error was reported as 0 were verified in that publication. The ranked ratios of CV*_ELEV/CV*_AMB ranged without abrupt jumps from 0.07 to 29.25, except for the same observations for PAP_NO 2363, for which the reported standard error of 0 was verified. The ranked ratios of N_ELEV/N_AMB ranged without abrupt jumps from 0.4 to 1.43. Thus, this analysis did not reveal any aberrant and unverifiable observations in the databases.

To search for possible confusion between standard error and standard deviation (see Sect. 3), coefficients of variation CV* (after Sokal & Rohlf 1981) were calculated, whenever possible, for each PARAM from each mean, standard deviation, and sample size. It was expected that, for any PARAM, an anomalously low coefficient of variation for a given observation might signal that a standard error was mis-labeled as a standard deviation. The database was sorted by PARAM, then by CV*_AMB and CV*_ELEV, and was inspected for jumps of greater than fourfold between adjacent observations. Where the standard error, rather than standard deviation, was reported in the cited publication, no mislabeling should have been possible. This analysis identified two pairs of adjacent observations that warranted further scrutiny. The following list contains those pairs of adjacent observations, along with the results of the checks.

PAP_NO = 3034
PARAM = PN
SPECIES = Echinochloa crusgalli
SOURCE = F1
X_ELEV = 44.400
SE_ELEV = 0.100
CV*_ELEV = 0.694

and

PAP_NO = 2723
PARAM = PN
SPECIES = Poa alpina
SOURCE = F4
X_ELEV = 40.120
SE_ELEV = 0.505
CV*_ELEV = 2.955

Data for both of the above observations were verified in the original publications./p>

PAP_NO = 2184
PARAM = TILLERS
SPECIES = Phleum pratense
SOURCE = T2
X_ELEV = 726.000
SE_ELEV = 52.000
CV*_ELEV = 28.203

and

PAP_NO = 2717
PARAM = TILLERS
SPECIES = Bromus erectus
SOURCE = F1
X_ELEV = 4.590
SE_ELEV = 0.400
CV*_ELEV = 129.991

Data for both of the above observations were verified in the original publications. However, the error bars in Fig. 1 of PAP_NO 2717 were not labeled as to their meaning; they were assumed to represent standard error (see Sect. 3).

5. Instructions for Obtaining the Data and Documentation

Download the data from here.

6. References

Cooper, H., and L. V. Hedges. 1994. The Handbook of Research Synthesis. Russell Sage Foundation, New York.
Curtis, P. S., and J. A. Teeri. 1992. Seasonal responses of leaf gas exchange to elevated carbon dioxide in Populus grandidentata. Canadian Journal of Forest Research 22:1320-1325.
Curtis, P. S., R. M. Cushman, and A. L. Brenkert. 1999. A Database of Woody Vegetation Responses to Elevated Atmospheric CO₂. ORNL/CDIAC-120, NDP- 072. Carbon Dioxide Information Analysis Center, U.S. Department of Energy, Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.
Gurevitch, J., and L. V. Hedges. 1993. Meta-analysis: Combining the results of independent experiments. Pages 378-398 in S. M. Scheiner and J. Gurevitch, editors. Design and Analysis of Ecological Experiments. Chapman and Hall, New York.
Gurevitch, J., L. L. Morrow, A. Wallace, and J. S. Walsch. 1992. A meta- analysis of competition in field experiments. American Naturalist 140:539-572.
Idso, S. B., and B. A. Kimball. 1992. Effects of atmospheric CO₂ enrichment on photosynthesis, respiration, and growth of sour orange trees. Plant Physiology 99:341-343.
Jones, M. H., P. S. Curtis, and E. A. Kellogg. Patterns of response to elevated CO₂ in the grasses (Poaceae). Submitted to The American Naturalist.
Mousseau, M., and B. Saugier. 1992. The direct effect of increased CO₂ on gas exchange and growth of forest tree species. Journal of Experimental Botany 43:1121-1130.
Sokal, R. R., and F. J. Rohlf. 1981. Biometry. W. H. Freeman and Company, New York.
Wand, S. J. E., G. F. Midgley, M. H. Jones, and P. S. Curtis. 1999. Responses of wild C4 and C3 grass (Poaceae) species to elevated atmospheric CO₂ concentration: a test of current theories and perceptions. Global Change Biology 5:723-741 (available online via Blackwell Science Ltd.'s Synergy subscription service).

7. Listing of Files Provided

The database consists of seven files (see Table 1), including this documentation file. The data files (ndp073.dat and ndp073.wk1), reference files (refs.dat and refs.wk1), and comment files (comments.dat and comments.wk1) are available in two formats: as flat ASCII files and as binary spreadsheet files (in Lotus 1-2-3 format, but readable by other spreadsheet programs).

The 30-field ndp073.dat and ndp073.wk1 files contain data (954 observations in all) relevant for CO₂-exposure meta-analysis for herbaceous plants. The ndp073.dat file can be read into SAS or Fortran programs, using the access codes provided in Sect. 11 of this numeric data package. The ndp073.dat file can also be converted into a spreadsheet file for processing, although it is simpler to use the corresponding ndp073.wk1 spreadsheet file provided. The refs.dat file (included in this report as Appendix B) and refs.wk1 file list the selected literature represented in the data file (119 references), and the comments.dat file (included in this report as Appendix C) and comments.wk1 file provide additional information about the studies, beyond what appears in the ndp073.dat and ndp073.wk1 data files. The reference numbers in the refs.dat, refs.wk1, comments.dat, and comments.wk1 files correspond to the paper numbers in the ndp073.dat and ndp073.wk1 data files.

8. Description of the Documentation File

The ndp073.txt (File 1) file is an ASCII text equivalent of this document.

9. Description, Format, and Partial Listings of the ASCII Data Files

Table 2 describes the format and contents of the ASCII data file ndp073.dat (File 2) distributed with this numeric data package. Table 2 also indicates the column in the corresponding spreadsheet file ndp073.wk1 in which each variable is found. The missing-value indicator in this database is the period (.), except for the real numeric fields SE_AMB, SD_AMB, CV*_AMB, SE_ELEV, SD_ELEV, and CV*_ELEV, in which the missing-value indicator is -9.99, and the integer numeric fields N_AMB and N_ELEV, in which the missing-value indicator is -9.

First two data records:

    38AGWT   G PLANT-1     TRITICUM     AESTIVUM     ANGIO GRASS_CC3   GRASS
330
660UL L-1       461.45         GC  SEED     H2O   LO     10 ML PL-1 D-1   F4
3.61   -9.99   -9.99  -9.99   10     5.13  -9.99   -9.99   -9.99    10  .
    38AGWT   G PLANT-1     TRITICUM     AESTIVUM     ANGIO GRASS_CC3   GRASS
330
660UL L-1       371.45         GC  SEED     H2O   CTL    40 ML PL-1 D-1   F4
2.98   -9.99   -9.99  -9.99   10     3.97  -9.99   -9.99   -9.99    10  .

Last two data records:

  3042PN     UMOL M-2 S-1  ZEA          MAYS         ANGIO GRASS_CC4   GRASS 330
640UBAR         305            GH  SEED     FERT  HI     .                F2
64.80    2.10    5.94   9.45    8    52.40   0.90    2.55    5.01     8  Y
  3042PN     UMOL M-2 S-1  ZEA          MAYS         ANGIO GRASS_CC4   GRASS 330
640UBAR         305            GH  SEED     FERT  LO     .                F2
27.90    1.84    5.20  19.24    8    21.90   2.10    5.94   27.97     8  Y

The refs.dat (File 4) ASCII file provides citations of papers included in the database. A full listing of the file is included as Appendix B.

The comments.dat (File 6) ASCII file provides experimental details from papers included in the database. A full listing of the file is included as Appendix C.

10. Description and Format of the Lotus 1-2-3 Binary Spreadsheet Files

Three Lotus 1-2-3 binary spreadsheet files (files 3, 5, and 7) contain the same information as the corresponding ASCII files (files 2, 4, and 6).

File ndp073.wk1 (File 3) corresponds to ASCII file ndp073.dat (File 2). Table 2, which describes the contents and format of ndp073.dat, also indicates the column of ndp073.wk1 in which each variable is found.

File refs.wk1 (File 5) corresponds to ASCII file refs.dat (File 4).

File comments.wk1 (File 7) corresponds to ASCII file comments.dat (File 6).

11. SAS and Fortran Codes to Access the Data

The following is SAS code to read file ndp073.dat:

*SAS data retrieval routine to read ndp073.dat;

data ndp073;
infile 'ndp073.dat';
input PAP_NO 6. @7 PARAM $char7. P_UNIT $ 14-27 GENUS $ 28-40
      SPECIES $ 41-53 DIV1 $ 54-59 DIV2 $ 60-66 DIV3 $ 67-71
      DIV4 $ 72-77 AMB $ 78-80 ELEV $ 81-84
      CO2_UNIT $ 85-94 TIME $ 95-99 POT $ 100-112 MTHD $ 113-116
      STOCK $ 117-125 XTRT $ 126-131 LEVEL $ 132-138 QUANT $ 139-155
      SOURCE $ 156-161 X_AMB 162-169 SE_AMB 170-177 SD_AMB 178-185
      CV_AMB 186-192 N_AMB 193-197 X_ELEV 198-206 SE_ELEV 207-213
      SD_ELEV 214-221 CV_ELEV 222-229 N_ELEV 230-235 SDC $ 236-238 ;

* In the above INPUT statement, the variables CV*_AMB and CV*_ELEV have
  been renamed CV_AMB and CV_ELEV, respectively.;

proc print;
run;

The following is Fortran code to read file ndp073.dat:

C *** Fortran program to read the file "ndp073.dat"
C
      INTEGER PAP_NO, N_AMB, N_ELEV
C
      REAL X_AMB, SE_AMB, SD_AMB, CV_AMB, X_ELEV, SE_ELEV,
     +     SD_ELEV, CV_ELEV
C
      CHARACTER PARAM*7, P_UNIT*14, GENUS*13, SPECIES*13, DIV1*6,
     + DIV2*7, DIV3*5, DIV4*6, AMB*3, ELEV*4, CO2_UNIT*10,
     + TIME*5,  POT*13, MTHD*4, STOCK*9, XTRT*6, LEVEL*7,
     + QUANT*17, SOURCE*6, SDC*3
C
      OPEN (UNIT=1, FILE='ndp073.dat')
C
C     Note that the variables CV*_AMB and CV*_ELEV have
C     been renamed CV_AMB and CV_ELEV, respectively
C
   10 READ (1,100,END=99) PAP_NO, PARAM, P_UNIT, GENUS, SPECIES,
     + DIV1, DIV2, DIV3, DIV4, AMB, ELEV, CO2_UNIT, TIME, POT,
     + MTHD, STOCK, XTRT, LEVEL, QUANT, SOURCE, X_AMB, SE_AMB,
     + SD_AMB, CV_AMB, N_AMB, X_ELEV, SE_ELEV, SD_ELEV, CV_ELEV,
     + N_ELEV, SDC
C
  100 FORMAT (I6,A7,A14,2A13,A6,A7,A5,A6,A3,A4,A10,A5,A13,A4,A9,
     + A6,A7,A17,A6,3F8.2,F7.2,I5,F9.2,F7.2,2F8.2,I6,A3)
C
      GO TO 10
   99 CLOSE (UNIT=1)
      STOP
      END

Appendix A: Species Included in Database

Agropyron caninum
Agropyron smithii
Agrostis capillaris
Andropogon gerardii
Avena barbata
Avena fatua
Avena sativa
Bouteloua curtipendula
Bouteloua eriopoda
Bouteloua gracilis
Briza subaristata
Bromus erectus
Bromus hordaeceus
Bromus willdenowii
Calamagrostis epigejos
Carex curvula
Dactylis glomerata
Digitaria macroblephara
Digitaria sanguinalis
Echinochloa crusgalli
Eleusine indica
Eriophorum vaginatum
Festuca arundinacea
Festuca durviscula
Festuca elatior
Festuca idahoensis
Festuca ovina
Festuca pratense
Festuca rupicola
Festuca vivipara
Hordeum vulgare
Lolium boucheanum
Lolium multiflorum
Lolium perenne
Nardus stricta
Oryza sativa
Panicum antidotale
Panicum laxum
Panicum millioides
Pascopyrum smithii
Paspalum dilatatum
Pennisetum clandestinum
Phalaris aquatica
Phleum pratense
Poa alpina
Poa annua
Poa pratensis
Puccinellia maritima
Rottboellia exaltata
Schizachyrium scoparium
Scirpus olneyi
Setaria faberi
Sorghum bicolor
Sorghum helpense
Spartina patens
Sporobolus kentrophyllus
Stipa occidentalis
Themeda triandra
Triticum aestivum
Vulpia microstachys
Zea mays

Appendix B: Full Listing of refs.dat

The number at the beginning of each entry corresponds to PAP_NO, the cited paper number, as defined in Sect. 9.

38. Andre, M., and H. Du Cloux. 1993. Interaction of CO2 Enrichment and Water
Limitations on Photosynthesis and Water-Use Efficiency in Wheat. Plant
Physiology and Biochemistry 31:103-112.

186. Drake, B. G. 1992. A Field Study of the Effects of Elevated CO2 on
Ecosystem Processes in a Chesapeake Bay Wetland. Australian Journal of Botany
40:579-595.

488. Nie, D., H. He, M. B. Kirkham, and E. T. Kanemasu. 1992. Photosynthesis
of a C3 Grass and a C4 Grass under Elevated CO2. Photosynthetica 26:189-198.

618. Ryle, G. J. A., C. E. Powell, and V. Tewson. 1992. Effect of elevated co2
on photosynthesis, respiration and growth of perennial ryegrass. Journal of
Experimental Botany 43:811-818.

754. Ziska, L. H., and J. A. Bunce. 1993. Inhibition of Whole Plant
Respiration by Elevated CO2 as Modified by Growth Temperature. Physiologia
Plantarum 87:459-466.

765. Baker, J. T., L. H. Allen Jr., and K. J. Boote. 1992. Response of Rice to
Carbon Dioxide and Temperature. Agricultural and Forest Meteorology
60:153-166.

2066. Samarakoon, A. B., W. J. Muller, and R. M. Gifford. 1995. Transpiration
and leaf area under elevated CO2: Effects of soil water status and genotype in
wheat. Australian Journal of Plant Physiology 22:33-44.

2119. Greer, D. H., W. A. Laing, and B. D. Campbell. 1995. Photosynthetic
responses of thirteen pasture species to elevated CO2 and temperature.
Australian Journal of Plant Physiology 22:713-722.

2125. Baxter, R., M. Gantley, T. W. Ashenden, and J. F. Farrar. 1994. Effects
of elevated carbon dioxide on three grass species from montane pasture.
Journal of Experimental Botany 45:1267-1287.

2132. Rao, M. V., B. A. Hale, and D. P. Ormrod. 1995. Amelioration of
ozone-induced oxidative damage in wheat plants grown under high carbon
dioxide. Plant Physiology 109:421-432.

2133. Tuba, Z., K. Szente, and J. Koch. 1994. Response of photosynthesis,
stomatal conductance, water use efficiency and production to long-term
elevated CO2 in winter wheat. Journal of Plant Physiology 144:661-668.

2158. Gloser, J., and M. Bartak. 1994. Net photosynthesis, growth rate and
biomass allocation in a rhizomatous grass Icalamagrostis epigejos grown at
elevated CO2 concentration. Photosynthetica 30(1):143-150.

2159. Ziska, L. H., and J. A. Bunce. 1994. Increasing growth temperature
reduces the stimulatory effect of elevated CO2 on photosynthesis or biomass in
two perennial species. Physiologia Plantarum 91:183-190.

2168. Knapp, A. K., E. P. Hamerlynck, and C. E. Owensby. 1993. Photosynthetic
and water relations responses to elevated CO2 in the C4 grass Andropogon
geradii. International Journal of Plant Science 154(4):459-466.

2184. Saebo, A., and L. M. Mortensen. 1995. Growth and regrowth of Phleum
pratense, Lolium perenne, Trifolium repens and Trifolium pratense at normal
and elevated O2 concentration. Agriculture, Ecosystems and Environment
55:29-35.

2192. Knapp, A. K., J. T. Fahnestock, and C. E. Owensby. 1994. Elevated
atmospheric O2 alters stomatal responses to variable sunlight in a C4 grass.
Plant, Cell and Environment 17:189-195.

2202. Wilsey, B. J., S. J. McNaughton, and J. S. Coleman. 1994. Will increases
in atmospheric O2 affect regrowth following grazing in C4 grasses from
tropical grasslands? Oecologia 99:141-144.

2208. Crush, J. R. 1994. Elevated atmospheric O2 concentration and rhizosphere
nitrogen fixation in four forage plants. New Zealand Journal of Agricultural
Research 37:455-463.

2211. Morgan, J. A., W. G. Knight, L. M. Dudley, and H. W. Hunt. 1994.
Enhanced root system C-sink activity, water relations and aspects fo nutrient
acquisistion in mycotrophic Bouteloua gracilis subjected to CO2 enrichment.
Plant and Soil 165:139-146.

2227. Bowler, J. M., and M. C. Press. 1993. Growth responses of two
contrasting upland grass species to elevated CO2 and nitrogen concentration.
New Phytologist 124:515-522.

2229. Mitchell, R. A. C., V. J. Mitchell, S. P. Driscoll, J. Franklin, and D.
W. Lawlor. 1993. Effects of increased CO2 concentration and temperature on
growth and yield of winter wheat at two levels of nitrogen application. Plant,
Cell and Environment 16:521-529.

2246. Baxter, R., T. W. Ashenden, T. H. Sparks, and J. F. Farrar. 1994.
Effects of elevated carbon dioxide on three montane grass species. Journal of
Experimental Botany 45 (272):305-315.

2300. Bassirirad, H., D. T. Tissue, J. F. Reynolds, and F. S. Chapin. 1996.
Response of Eriophorum vaginatum to CO2 enrichment at different soil
temperature: effects on growth, root respiration and PO-4 uptake kinetics. New
Phytologist 133:423-430.

2312. Wilsey, B. J. 1996. Urea additions and defoliation affect plant
responses to elevated CO2 in a C3 grassland from Yellowstone National Park.
Oecologia 108:321-327.

2315. Casella, E., J. F. Soussana, and P. Loiseau. 1996. Long-term effects of
CO2 enrichment and temperature increase on a temperate grass sward. 1.
Productivity and water use. Plant and Soil 182:83-99.

2316. Soussana, J. F., E. Casella, and P. Loiseau. 1996. Long-term effects of
CO2 enrichment and temperature increase on a temperate grass sward. 2. Plant
nitrogen budgets and root fraction. Plant and Soil 182:101-114.

2329. Jones, M. B., M. Jongen, and T. Doyle. 1996. Effects of elevated carbon
dioxide concentrations on agricultural grassland production. Agricultural and
Forest Meteorology 79:243-252.

2330. Stewart, J., and C. Potvin. 1996. Effects of elevated CO2 on an
artificial grassland community: competition, invasion and neighbourhood area.
Functional Ecology 10:157-166.

2337. Saebo, A., and L. M. Mortensen. 1996. The influence of elevated CO2
concentration on growth of seven grasses and one clover species in a cool
maritime climate. Acta Agriculturae Scandinavia Section B-Sorland Plant
Science 46:49-54.

2341. Schappi, B., and C. Korner. 1996. Growth responses of an alpine
grassland to elevated CO2. Oecologia 105:43-52.

2342. Jackson, R. B., and H. L. Reynolds. 1996. Nitrate and ammonium uptake
for single and mixed species communities grown at elevated CO2. Oecologia
105:74-80.

2345. Hakala, K., and T. Mela. 1996. The effects of prolonged exposure to
elevated temperatures and elevated CO2 leveles on the growth, yield and dry
matter partitioning of filed-sown meadow fescue. Agricultural and Food Science
in Finland 5(3):285-298.

2347. Jackson, R. B., Y. Luo, Z. G. Cardon, O. E. Sala, C. B. Field, and H. A.
Mooney. 1995. Photosynthesis, growth and density for the dominant species in a
CO2 enriched grassland. Journal of Biogeography 22:221-225.

2350. Teughels, H., I. Nijs, P. Van Hecke, and I. Impens. 1995. Competition in
a global change environment: The importance of different plant traits for
competitive success. Journal of Biogeography 22:297-305.

2351. Campbell, B. D., W. A. Laing, D. H. Gree, J. R. Crush, H. Clark, D. Y.
WIlliamson, and M. D. J. Given. 1995. Variation in grassland populations and
species and the implications for community responses to elevated CO2. Journal
of Biogeography 22:315-322.

2357. Chu, C. C., C. B. Field, and H. A. Mooney. 1996. Effects of CO2 and
nutrient enrichment on tissue quality of two California annuals. Oecologia
107:433-440.

2358. Ferris, R., I. Niy, T. Bejaeghe, and I. Impens. 1996. Contrasting CO2
and temperature effects on leaf growth of perennial rye grass in spring and
summer. Journal of Experimental Botany 47:1033-1043.

2362. Wheeler, T. R., G. R. Batts, R. H. Ellis, P. Hadley, and J. J. L.
Morison. 1996. Growth and yield of winter wheat (Triticum aestium) crops in
response to CO2 and temperature. Journal of Agricultural Science 127:37-48.

2363. Volin, J. C., and P. B. Reich. 1996. Interaction of elevated CO2 and O3
on growth, photosynthesis and respiration of three perennial species grown in
low and high nitrogen. Physiologia Plantarum 97:674-684.

2364. Miglietta, F., A. Giuntoli, and M. Bindi. 1996. The effect of free air
carbon dioxide enrichment (FACE) and soil nitrogen availability on the
photosynthetic capacity of wheat. Photosynthesis Research 47:281-290.

2366. Ziska, L. H., W. Weerakoon, O. S. Namuco, and R. Pamplona. 1996.
Influence of nitrogen on the elevated CO2 response in field-grown rice.
Australian Journal of Plant Physiology 23:45-52.

2367. Saebo, A., and L. M. Mortensen. 1996. Growth, morphology and yield of
wheat, barley and oats grown at elevated atmospheric CO2 concentration in a
cool maritime climate. Agriculture, Ecosystems and Environment 57:9-15.

2369. Ziska, L. H., P. A. Manalo, and R. A. Ordonez. 1996. Intraspecific
variaiton in the response of rice (Oryza sativa L) to increased CO2 and
temeprature: growth and yield response of seventeen cultivars. Journal of
Experimental Botany 47:1353-1359.

2372. Nijs, I., H. Teughels, H. Blum, G. Hendrey, and I. Impens. 1996.
Simulation of climate change with infrared heaters reduces the productivity of
Lolium perenne L in summer. Environmental and Experimental Botany 36:271-280.

2379. Veisz, O., N. Harnos, L. Szunies, and T. Tischner. 1996. Overwintering
of winter cereals in Hungary in the case of global warming. Euphytica
92:249-253.

2383. Nijs, I., and I. Impens. 1996. Effects of elevated CO2 concentration and
climate-warming on photosynthesis during winter in Lolium perenne. Journal of
Experimental Botany 47:915-924.

2387. Leadley, P. W., and J. Stocklin. 1996. Effects of elevated CO2 on model
calcareous grasslands: Community, species, and genotype responses. Global
Change Biology 2:389-397.

2395. Tuba, Z., K. Szente, Z. Nagy, Z. Csintalan, and J. Koch. 1996. Responses
of CO2 assimilation, transpiration and water use efficiency to long-term
elevated CO2 in perennial C3 xeric loess steppe species. Journal of Plant
Physiology 148:356-361.

2398. Mortensen, L. M., and A. Saebo. 1996. The effects of elevated CO2
concentration on growth of Phleum pratense L. in different parts of the growth
season. Acta Agriculturaie Scandinavia Section B-Soil and Plant Science
46:128-134.

2401. Jackson, R. B., and A. L. Reynolds. 1996. Nitrate and annomium uptake
for single- and mixed species communities grown at elevated CO2. Oecologia
105:74-80.

2403. Fanymeier, A., U. Geuters, U. Hesstein, H. Sandhagel, A. Hoffmann, B.
Vermebren, and A. J. Jager. 1996. Effects of elevated CO2, nitrogen supply and
tropospheric ozone on spring wheat. 1. Growth and Yields. Environmental
Pollution 91:381-390.

2407. Kinball, B. A., P. J. Pinter, R. L. Garcia, R. L. La Mort, G. W. Wall,
D. J. Hunsaker, G. WEchsung, F. Wechsung, and T. Kartschall. 1995.
Productivity and water use of wheat under free-air CO2 enrichment. Global
Change Biology 1:429-442.

2420. Hunt, H. W., E. T. Elliot, J. K. Detling, J. A. Morgan, and D. X. Chen.
1996. Responses of a C3 and a C4 perennial grass to elevated CO2 and
temperature under different water regimes. Global Change Biology 2:35-47.

2427. Samarakoon, A. B., and R. M. Gifford. 1996. Elevated CO2 effects on
water use and growth of maize in wet and drying soils. Australian Journal of
Plant Physiology 23:53-62.

2430. Ruget, F., O. Bethenod, and L. Combe. 1996. Repercussions of increased
atmospheric CO2 on maize morphogenesis and growth for various temperature and
radiation levels. Maydica 41:181-191.

2440. Frank, A. B., and A. Bauer. 1996. Temperature, nitrogen and carbon
dioxide effects on spring wheat development and spikelet numbers. Crop Science
36:659-665.

2441. Read, J. J., and J. A. Morgan. 1996. Growth and partitioning in
Pascopyrum smithii (C3) and Bouteloua graciles (C4) as influenced by carbon
dioxide and temperature. Annals of Botany 77:487-496.

2443. Polley, H. W., H. B. Johnson, H. S. Mayeux, D. A. Brown, and J. W. C.
White. 1996. Leaf and plant water use efficiency of C4 species grown at
glacial to elevated CO2 concentrations. International Journal of Plant
Sciences 157:164-170.

2444. Bowler, J. M., and M. C. Press. 1996. Effects of elevated CO2 nitrogen
form and concentration on growth and photosynthesis of a fast- adn
slow-growing grass. New Phytologist 132:391-401.

2448. RowlandBamford, A. J., J. T. Baker, H. L. Allen, and G. Bowes. 1996.
Interactions of CO2 enrichment and temperature on carbohydrate accumulation
and partitioning in rice. Environmental and Experimental Botany 36:111-124.

2454. Bagash, D. Z., M. J. Paul, M. A. J. Parry, A. J. Keys, and D. W. Lawlor.
1995. Increased capacity for photosynthesis in wheat grown at elevated CO2.
The relationship between electron-transport and carbon metabolism. Planta
197:482-489.

2468. Rao, M. V., and L. J. Dekok. 1994. Interactive effects of high CO2 and
SO2 on growth and antioxidant levels in wheat. Phyton-Annales Rei Botanicae
34:279-290.

2474. Newbery, R. M., J. Wolfenden, T. A. Mansfield, and A. F. Harrison. 1995.
Nitrogen, phosphorus and potassium uptake and demand Agrostis capillaria. The
influence of elevated CO2 and nutrient supply. New Phytologist 130:565-574.

2480. Lenssen, G. M., W. E. Vandium, P. Jak, and J. Roxema. 1995. The response
of Aster tripolium and Puccinellia maritima to atmospheric carbon dioxide
enrichment and their interaction with flooding and salinity. Aquatic Botany
50:181-192.

2492. Schenk, U., R. Maderscheid, J. Hugen, and H. J. Weigel. 1995. Effects of
CO2 enrichment and intraspecific competition on biomass partitioning, nitrogen
content, and microbial biomass carbon in soil of perennial rye grass and white
clover. Journal of Experimental Botany 46:987-993.

2502. Jacob, J., C. Greitner, and B. G. Drake. 1995. Acclimation of
photosynthesis in relation to Rubisco and non-structural carbohydrate contents
and in-situ carboxylase activity in Scirpus olnei grown at elevated CO2 in the
field. Plant, Cell and Environment 18:875-884.

2503. Jongen, M., M. B. Jones, T. Hebeisen, H. Blum, and G. Hendrey. 1995. The
effects of elevated CO2 concentrations on the root growth of Lolium perenne
and Trifolium repens grown in a FACE system. Global Change Biology 1:361-371.

2504. Kleemola, J., J. Peltonen, and P. Peltonen-Sainio. 1994. Apical
development and growth of Barley under different CO2 and nitrogen regimes.
Journal of Agronomy and Crop Science 173:79-92.

2510. Demothes, M. A. G., and D. Knoppik. 1994. Effects of long term enhanced
CO2 partial pressure on gas exchange parameters and saccharide pools of wheat
leaves. Photosynthetica 30:435-445.

2521. Balaguer, L., J. D. Barnes, A. Panicucci, and A. M. Borland. 1995.
Production and utilization of assimilates in wheat leaves exposed to elevated
O3 and/or CO2. New Phytologist 129:557-568.

2522. Barnes, J. D., J. H. Ollerenshaw, and C. P. Whitfield. 1995. Effects of
elevated CO2 and/or O3 on growth, development and physiology of wheat. Global
Change Biology 1:129-142.

2525. Hattenschwiler, S., and C. Korner. 1996. System-level adjustments to
elevated CO2 in model spruce ecosystems. Global Change Biology 2:377-387.

2531. Owensby, C. E., P. I. Coyne, J. M. Ham, L. M. Avea, and A. K. Knapp.
1993. Biomass production in a tallgrass prairie ecosystem exposed to ambient
and elevated CO2. Ecological Applications 3:644-653.

2541. Jackson, R. B., O. E. Sala, C. B. Field, and H. A. Mooney. 1994. CO2
alters water use, carbon gain, and yield for the dominant species in a natural
grassland. Oecologia 98:257-262.

2547. Baker, J. T., L. H. Allen, and K. J. Boote 1992. Temperature effects on
rice at elevated CO2 concentration. Journal of Experimental Botany 43:959-964.

2579. Billes, G., H. Rouhier, and P. Bottner. 1993. Modifications of the
carbon and nitrogen allocations in the plant Triticum aestivum L. soil system
in response to increased atmospheric CO2 concentration. Plant and Soil
157:215-225.

2580. Baker, J. T., S. L. Albrecht, D. Pan, L. H. Allen, N. B. Pickering, and
K. J. Boote. 1994. Carbon dioxide and temperature effects on rice (Oryza
sativa L., CV 1R-72). Soil and Crop Science Society of Florida, Proceedings
53:90-97.

2595. Santruce, J., H. Santurckova, J. Kueton, M. Simkoua, and K. Rohacek.
1994. The effect of elevated CO2 concentration on photosynthetic CO2 fixation,
respiration and carbon economy of wheat plants. Rostlinna Vyroba 40:689-696.

2597. Ingaurdsen, C., and B. Veierskov. 1994. Response of young barley plants
to CO2 enrichment. Journal of Experimental Botany 45:1373-1378.

2644. Reeves, D. W., H. H. Royers, S. A. Prior, C. W. Wood, and G. B. Runion.
1994. Elevated atmospheric carbon dioxide effects on sorghum and soybean
nutrient status. Journal of Plant Nutrition 17:1939-1954.

2654. Jackson, R. B., Y. Lou, Z. G. Cardon, O. E. Sala, C. B. Field, and H. A.
Mooney. 1995. Photosynthesis, growth and density for the dominant species in a
CO2 enriched grassland. Journal of Biogeography 22:221-225.

2666. Samarakoon, A. B., and R. M. Gifford. 1995. Soil water content under
plants at high CO2 concentrations and interaction with the direct CO2 effects:
A species comparison. Journal of Biogeography 22:193-202.

2669. Schenk, U., A. J. Jager, and H. J. Weigel. 1996. Nitrogen supply
determine responses of yeild and biomass partitioning of perennial rye grass
to elevated atmospheric carbon dioxide concentrations. Journal of Plant
Nurtition 19:1423-1440.

2692. Kimball, B. A., P. J. P. Pinter, R. L. Garcia, R. L. LaMorte, G. W.
Wall, D. J. Hunsaker, G. Wechsung, F. Wechsong, and T. Kartschall. 1995.
Productivity and water use of wheat under free-air CO2. Global Change Biology
1:429-442.

2698. Potvin, C., and L. Vasseur. 1997. Long-term CO2 enrichment of a pasture
community: species richness, dominance, and succession. Ecology 78:666-677.

2709. Hebeisen, T., A. Luscher, and J. Nosberger. 1997. Effects of elevated
atmospheric CO2 and nitrogen fertilisation on yield of Trifolium repens and
Lolium perenne. Acta Oecologica/Oecologia Plantarum 18:277-284.

2710. Hebeisen, T., A. Luscher, S. Zanetti, B. U. Fischer, U. A. Hartwig, M.
Frehner, G. R. Hendrey, H. Blum, and J. Nosberger. 1997. Growth response of
Trifolium repens L and Lolium perenne L as monocultures and bi-species mixture
to free air CO2 enrichment and management. Global Change Biology 3:149-160.

2711. Ghannoum, O., S. vonCaemmerer, E. W. R. Barlow, and J. P. Conroy. 1997.
The effect of CO2 enrichment and irradiance on the growth, morphology and gas
exchange of a C3 (Panicum laxum) and a C4 (Panicum antidotale) grass.
Australian Journal of Plant Physiology 24:227-237.

2715. Cotrufo, M. F., and A. Gorissen. 1997. Elevated CO2 enhances
below-ground C allocation in three perennial grass species at different levels
of N availibility. New Phytologist 137:421-431.

2718. Wilsey, B. J., J. S. Coleman, and S. J. McNaughton. 1997. Effects of
elevated CO2 and defoliation of grasses: A comparative ecosystem approach.
Ecological Applications 7:844-853.

2723. Stirling, C. M., P. A. Davey, T. G. Williams, and S. P. Long. 1997.
Acclimation of photosynthesis to elevated CO2 and temperature in five British
native species of contrasting functional type. Global Change Biology
3:237-246.

2735. Nijs, I., and I. Impens. 1997. An analysis of the balance between root
and shoot activity in Lolium perenne cv Melvina. Effects of CO2 concentration
and air temperature. New Phytologist 135:81-91.

2737. Mortensen, L. M. 1997. Effects of carbon dioxide concentrations on three
grass species grown in mixture in two soil types at different ozone
concentrations or temperatures. Acta Agriculturae Scandinavica, Section B,
Soil and Plant Sciences 47:14-19.

2756. Hamerlynck, E. P., C. A. McAllister, A. K. Knapp, J. M. Ham, and C. E.
Owensby. 1997. Photosynthetic gas exchange and water relation responses of
three tallgrass prairie species to elevated carbon dioxide and moderate
drought. International Journal of Plant Sciences 158:608-616.

2758. Stocker, R., P. W. Leadley, and C. Korner. 1997. Carbon and water fluxes
in a calcareous grassland under elevated CO2. Functional Ecology 11:222-230.

2785. Hungate, B. A., J. Canadell, and F. S. Chapin. 1996. Plant species
mediate changes in soil microbial N in response to elevated CO2. Ecology
77:2505-2515.

2793. Fitter, A. H., G. K. Self, J. Wolfenden, M. M. I. vanVuuren, T. K.
Brown, L. Williamson, J. D. Graves, and D. Robinson. 1996. Root production and
mortality under elevated atmospheric carbon dioxide. Plant and Soil
187:299-306.

2802. Casela, E., and J. F. Soussana. 1997. Long-term effects of CO2
enrichment and temperature increase on the carbon balance of a temperate grass
sward. Journal of Experimental Botany 48:1309-1321.

2821. Schapendonk, A. H. C. M., P. Dijkstra, J. Groenwold, C. S. Pot, and S.
C. vandeGeijn. 1997. Carbon balance and water use effciency of frequently cut
Lolium perenne L swards at elevated carbon dioxide. Global Change Biology
3:207-216.

2834. Baxter, R., T. W. Ashenden, and J. F. Farrar. 1997. Effect of elevated
CO2 and nutrient status on growth, dry matter partitioning and nutrient
content of Poa alpina var vivipara L. Journal of Experimental Botany
48:1477-1486.

2835. Bassirirad, H., J. F. Reynolds, R. A. Virginia, and M. H. Brunelle.
1997. Growth and root NO3- and PO43- uptake capacity of three desert species
in response to atmospheric CO2 enrichment. Australian Journal of Plant
Physiology 24:353-358.

2839. Lin, W. H., L. H. Ziska, O. S. Namuco, and K. Bai. 1997. The interaction
of high temperature and elevated CO2 on photosynthetic acclimation of single
leaves of rice in situ. Physiologia Plantarum 99:178-184.

2855. Wolf, J. 1996. Effects of nutrient supply (NPK) on spring wheat response
to elevated atmospheric CO2. Plant and Soil 185:113-123.

2856. Nakamura, T., M. Osaki, T. Koike, Y. T. Hanba, E. Wada, and T. Tadano.
1997. Effect of CO2 enrichment on carbon and nitrogen interaction in wheat and
soybean. Soil Science and Plant Nutrition 43:789-798.

2892. McKee, I. F., J. F. Bullimore, and S. P. Long. 1997. Will elevated CO2
concentrations protect the yield of wheat from O3 damage? . Plant, Cell and
Environment 20:77-84.

2893. Manderscheid, R., and H. J. Weigel. 1997. Photosynthetic and growth
responses of old and modern spring wheat cultivars to atmospheric CO2
enrichment. Agriculture, Ecosystems and Environment 64:65-73.

2895. Sicher, R. C., and J. A. Bunce. 1997. Relationship of photosynthetic
acclimation to changes of Rubisco activity in field-grown winter wheat and
barley during growth in elevated carbon dioxide. Photosynthesis Research
52:27-38.

2911. Mulholland, B. J., J. Craigon, C. R. Black, J. J. Colls, J. Atherton,
and G. Landon. 1997. Impact of elevated atmospheric CO2 and O3 on gas exchange
and chlorophyll content in spring wheat (Triticum aestivum L). Journal of
Experimental Botany 48:1853-1863.

2919. VanVuuren, M. M. I., D. Robinson, A. H. Fitter, S. D. Chasalow, L.
Williamson, and J. A. Raven. 1997. Effects of elevated atmospheric CO2 and
soil water availability on root biomass, root length, and N, P and K uptake by
wheat. New Phytologist 135:455-465.

2924. Vu, J. C. V., L. H. Allen, K. J. Boote, and G. Bowes. 1997. Effects of
elevated CO2 and temperature on photosynthesis and Rubisco in rice and
soybean. Plant, Cell and Environment 20:68-76.

2928. Ziska, L. H., O. Namuco, T. Moya, and J. Quilang. 1997. Growth and yield
response of field-grown tropical rice to increasing carbon dioxide and air
temperature. Agronomy Journal 89:45-53.

2935. Baker, J. T., L. H. Allen, K. J. Boote, and N. B. Pickering. 1997. Rice
responses to drought under carbon dioxide enrichment. 1. Growth and yield.
Global Change Biology 3:119-128.

3033. Patterson, D. T., and E. P. Flint. 1980. Potential effects of global
atmospheric CO2 enrichment on the growth and competitiveness of C3 and C4 weed
and crop plants. Weed Science 28:71-75.

3034. Potvin, C., and B. R. Strain. 1985. Photosynthetic response to growth
temperature and CO2 enrichment in two species of C4 grasses. Canadian Journal
of Botany 63:483-487.

3035. Potvin, C., and B. R. Strain. 1985. Effects of CO2 enrichment and
temperature on growth in two C4 weeds, Enchinochloa crus-galli and Eleusine
indica. Canadian Journal of Botany 63:1495-1499.

3036. Sionit, N., and D. T. Patterson. 1984. Responses of C4 grasses to
atmospheric CO2 enrichment. I. Effect of irradiance. Oecologia 65:30-34.

3038. Carter, D. R., and K. M. Peterson. 1983. Effects of a CO2 enriched
atmosphere on the growth and competitive interaction of a C3 and a C4 grass.
Oecologia 58:188-193.

3041. Morison, J. I. L., and R. M. Giford. 1984. Plant growth and water use
with limited water supply in high CO2 concentrations. II. Plant dry weight,
partitioning, and water use efficiency. Australian Journal of Plant Physiology
11:375-384.

3042. Wong, S. C. 1979. elevated atmospheric partial pressure of CO2 and plant
growth. I. Interactions of nitrogen nutrition and photosynthetic capacity in
C3 and C4 plants. Oecologia 44:68-74.

Appendix C: Full Listing of comments.dat