FREE AIR CO2 ENRICHMENT (FACE) DATA REPORT:
                           NITROGEN CONCENTRATIONS 
                      LEAVES, LITTER, FINE ROOTS, WOOD  

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DESCRIPTION OF FILE 
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This report documents the file, Nconc.dat, which contains the nitrogen  
concentration data for leaves, litter, fine roots, and wood produced in 
1998-2009.  These data were collected for rings 1 and 2 which are 
exposed to elevated CO2 and rings 3-5 which have ambient CO2.

This file updates the previously posted file with the addition of data from 2008-2009 and revised data based on re-analysis of wood samples and a new calculation of fine-root N based on a relationship with root diameter.


Additional information describing this dataset can be found in 
Norby, R.J. and C.M. Iversen (2006).  Nitrogen uptake, distribution, 
turnover, and efficiency of use in a CO2-enriched sweetgum forest. 
Ecology 87:5-14.
and 
Iversen CM, Ledford J, Norby RJ. 2008. CO2 enrichment increases carbon and nitrogen input from fine roots in a deciduous forest. New Phytologist 179: 837-847.

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CONTENTS OF THE ASCII DATA FILE
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Variable   Variable  Variable  Starting  Ending  Units Definition and
           type      width     column    column         comments

PLOT         Integer   1         3         3           Plot number
YEAR         Integer   4         6         9       y   Year
leaf_N       Real      6         11        16      %   Leaf nitrogen 
litter_N     Real      6         19        24      %   Litter nitrogen 
fine-root_N  Real      6         29        34      %   Fine root nitrogen 
wood_N       Real      6         42        47      %   Wood nitrogen 


PARTIAL LISTING OF THE ASCII DATA FILE
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The missing-value indicator for the variables in this file is -.999. 


Format and contents of the ASCII data file Nconc.dat.

First two data records:

1998  1.550   0.872   0.548   0.147  
1998  1.528   0.857   0.677   0.146
Last two data records:

2008   1.382  0.708   0.892   0.091
2008   1.235  0.624   0.753   0.084
SPREADSHEET SOFTWARE TO ACCESS THE DATA
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Since this nitrogen concentration file is space-delimited ASCII 
text, the files can be imported to spreadsheet software such as Excel.
A search and replace command can be used to replace the missing value 
of -.999 with an appropriate missing value for the software being used. 


SAS and FORTRAN CODES TO ACCESS THE DATA
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The following is SAS code to read the file, Nconc.dat.

/* SAS code to read Nconc.dat */

/*   Input Variables: */
/*         plot      - Plot number     */
/*         year      - Year            */
/*         leafN     - leaf N (%)      */
/*         litterN   - litter N (%)    */
/*         finerootN - fine root N (%) */
/*         woodN     - wood N (%)      */
 
data Nconc;

   infile "Nconc.dat";
   if _N_ = 1 then do;
      /* Read header records. */
      input ////////;
   end;

   input plot 1-3 year 6-9 leafN 11-16 3 litterN 19-24 3 finerootN 29-34 3 woodN 42-47 3;

proc print;

run;


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The following is FORTRAN code to read the file, Nconc.dat.

      program Nconc 
      implicit none

!     This program reads the file, Nconc.dat.

!     Input variables for data record:
!           plot      - Plot number
!           year      - Year
!           leafN     - Leaf N (%) 
!           litterN   - Litter N (%)  
!           finerootN - Fine root N (%) 
!           woodN     - Wood N (%) 

      real    :: leafN, litterN, finerootN, woodN 
      integer :: plot, year, nrec, ioerror

      open(unit = 10, file = 'Nconc.dat',&
         &status = 'old', iostat = ioerror)

      if(ioerror < 0) then
         write(6,'("Error opening input file.")')
         stop
      endif

!     input header records
      read(10,'(////////)')

      if(ioerror /= 0) then
         write(6,'("Input error reading header records.")')
         stop
      endif

      nrec = 0   !initialize counter for summing number of input records
   10 continue

      read(10,'(i3,2x,i4,1x,f6.3,2x,f6.3,4x,f6.3,7x,f6.3)', &
        & iostat = ioerror)&
        & plot, year, leafN, litterN, finerootN, woodN 
      
      if(ioerror < 0) then
         write(6,'("End-of-file")')
         write(6,'("Number of data records read = ", i5)') nrec
        stop
      endif

      write(6,'(i3,2x,i4,1x,f6.3,2x,f6.3,4x,f6.3,7x,f6.3)')&
         & plot, year, leafN, litterN, finerootN, woodN 
      nrec = nrec + 1
      go to 10   !read next record

      close (10)

      stop
      end


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