Free Air Respiratory Carbon Isotope Enrichment Experiment by fsy40675

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									   Free Air Respiratory Carbon
 Isotope Enrichment Experiment

  Leonel da S. L. Sternberg and Tara Greaver
                Dept of Biology,
              University of Miami

       Bruce Schaffer and Tomas Moreno
Tropical Research and Education Center (TREC),
               University of Florida
Measuring Net Ecosystem Exchange of Carbon Dioxide




                        Eddy Covariance technique
                        measures total NEE, but components of
                        NEE remain unknown
                                    ?        ?
                            NEE = Rgross- Pgross

                        Isotopic mass balance
                        equations can be used to
                        partition Rgrossand Pgross
    Currently, recycling is not considered in the mass balance
                    approach to partition NEE.

CO2 isotope            •Recycling enriches the isotopic value of respired CO2
values enriched        leaving the canopy.
from that of
source                 •Are estimations of Rgross and Pgross inaccurate when
                       recycling is not considered?
Vegetation
discriminates
against the
heavier
isotopes

                                         dR-D*ln(1-FR)




Source respiredCO2
              Definitions of Recycling

    LEAF LEVEL               ECOSYSTEM LEVEL

                                   PC        RC
                                        RP



      t
          r                                     R

Leaf = (x*t)+((1-x)*r)      Photosynthesis based
                                  FP = RP / (PC+RP)
                                  FP = BR/B
                            Respiration based
                                  F R = RP / R
                                  FR= (BR*%C)/(12*R)
Partitioning NEE by isotopic mass balance:

No Recycling
                                                    PC
   NEE=RGross-PGross=RC-PC                                        RC

    Isotopic Mass Balance                                    RP
    NEE* dE =(RC * dR )-(PC*(dC-D))

Recycling
                                                                      R
  NEE=RGross-PGross=RC+RP-RP –PC=RC-PC
     Isotopic Mass Balance
      NEE*dE=(RC*(dR-D*ln(1-F))+(RP*dabs) – (RP*dabs) – (PC*(dC-D))
               =(RC*(dR-D*ln(1-F)) – (PC*(dC-D))



•Recycling does not affect value of NEE, but does affect
isotopic values of its components, Rc and Pc
HOW TO MEASURE RECYCLING
     USING ISOTOPES?
• INSTANTANEOUS RECYCLING
 – Theoretical method
   Sternberg 1989, Sternberg et al. 1997
• INTEGRATED RECYCLING
 – Empirical method
   • New method developed in this work
    INSTANTANEOUS RECYCLING VALUES

             100%




d13CE ‰

             0%




                          1/[CO2]E
          THEORETICAL MODEL BASED ON THE
               FOLLOWING EQUATIONS

                    Keeling Equation
            dE= 1/[CO2]E *{[CO2]C*(dC -dR)}+dR

 Recycling Equation: derived from keeling equation
 dE= 1/[CO2]E *{[CO2]C*(dC -dR)*(1-FR)}+dR+(D*FR)
                 INTEGRATED RECYCLING VALUES
                     experimental manipulation

Treatment vegetation plot
                                           B*dB= (BC*(dC – D)) + (BR*(dR – D))
Isotopic Composition of Respired
Carbon Dioxide elevated by
experimental manipulation


Control vegetation plot                    B*dB= (BC*(dC – D)) + (BR*(dR – D))

Ambient conditions

Photosynthetic based recycling                (dB – dB)/(dR – dR)=BR/B= FP
Solving the Two Equations Simultaneously


 Respiratory based recycling                  FR=(FP*B*%C)/(R*12)
              Research Goals
• Document Recycling

• Compare methods of calculating Recycling
  – instantaneous (theoretical)
  – integrated (empirical) – new method developed here


• Determine how recycling affects isotopic mass
  balance equation in the calculation of Rgross and
  Pgross
Experimental Design




                            flow
                            meter
                                    50% Carbon-13
                                    and Nitrogen
  10
   me
     ter
       s




                       rs
                   mete
              10
                     Measurements
•   Instantaneous Recycling Index
    Control Plot Only

    .
•   Integrated Recycling Index
    Both Plots


•   Gross Photosynthesis and
    Respiration.
    Control Plot Only
                       RESULTS: Keeling Plot


                   0    0.0005   0.001   0.0015    0.002     0.0025   0.003   0.0035   0.004
              0


              -5


             -10
Delta 13 C




             -15


             -20
                                                             y = 6767.15 x -26.16,

             -25                                             n=74
                                                             R=9.7
             -30
                                                  1/ [CO2]




             Open Symbol= day time, Closed symbol =night time
                      -29
                    -29.2
                                LEAF
                                                                              Results:
                                                                              Biomass δ 13C
                    -29.4
                    -29.6
                    -29.8
                      -30
                    -30.2
                                                                              Internal leaf [CO2]
                    -30.4
                            0             5            10          15   20

                     -29
                                                                                  250
Delta C-13 (o/oo)




                    -29.2                                                         248
                                STEM
                    -29.4                                                         246
                    -29.6                                                         244
                    -29.8                                                         242




                                                                             Ci
                                                                                  240
                     -30
                                                                                  238
                    -30.2
                                                                                  236
                    -30.4
                                                                                  234
                    -30.6                                                         232
                            0             5            10          15   20        230
                                                                                        Treatment    Control
                    -27.8

                     -28           ROOT

                    -28.2

                    -28.4

                    -28.6                                                    •Treatment     biomass more
                    -28.8                                                    enriched than that of control
                     -29
                            0             5            10          15   20

                                              Distance From Edge
                                                                             • Enrichment due to treatment,
                                                                             not physiology
                 Calculation Integrated FR
d13CBiomass Control         measured                            -30.1± 0.08
d13CBiomass Treatment       measured                            -29.2± 0.03
d13CRespiration Control     Keeling Plot   y = 6767.2 x – 26.2 -26.2± 1.35

d13CRespiration Treatment   Keeling Plot   y = 5524.2 x -22.9   -22.9± 4.02
                            R=0.48     P<0.01

FP Integrated               (dB-dB)/(dR-dR)=(BR/B)              0.26
FR Integrated               (FP*B*%C)/(R*12)                    0.71
Compared to,

FR Instantaneous            Based on Deviation from Keeling
                            Equation                            0.48±0.12
                     RESULTS: Recycling affects isotopic mass balance
                     calculation of Canopy Level Photosynthesis (Pc)
Recycling Theory     PC=(B.C.*(dB-dR))/(dR-dC+DE) PC=(B.C.*(dB-dDN))/(dDN-dC+DE)
                     converted to mmoles/m2s PC converted to mmoles/m2s
CO2 isotope values
enriched from that   = 180.8 mmoles/m2s           PC = 36.1 mmoles/m2s
of source
                                                               δD= -3.04 ‰
                            δR = -26.16 ‰
 Pc                                                            δDN = -21.03 ‰

Vegetation
discriminates
against the
heavier
isotopes




                             δR = -26.16 ‰                     δR= -26.16 ‰

Source respiredCO2    No Recycling (F R=0)          Recycling (F R>0)
          Calculating Gross Respiration AND
                Gross Photosynthesis

RECYCLING                               NO RECYCLING
RC= (1-FR)*Rgr+ Rgr                     G.P. = PC
Rgr= RC/(2-FR)                          G.R. = RC
G.P. = PC+(FR*Rgr.)= 43.7 mmoles/m2s
G.R.= 2*Rgr= 10.6 mmoles/m2s


            PC       (1-FR)*Rgr.       PC           Rgr.




                 FR*Rgr.

                           Rgr.                            Rgr.
                  CONCLUSIONS
• Recycling of Carbon dioxide       Instantaneous FR                0.48
  can be very high
                                    Integrated FR                   0.71


                                                     Gross P        Gross Rsoil
                                                    (μmol m-2s-1)   (μmol m-2s-1)
• Recycling must be taken into
  account to accurately partition
  NEE into Gross Respiration
  and Photosynthesis by Isotope     Chamber            39.3             8.4
  Mass Balance.                     Resp.
                                    +Carbon
                                    Biomass

                                    Recycling          43.7            10.6


                                    NO               180.8            79.1
                                    Recycling
   FUTURE DIRECTION
• SCALE UP TO A PINE PLANTATION
– INCREASE THE AREA AND TIME OF
  FUMIGATION.
– MORE INTENSE MESUREMENTS OF SOIL
  BOLE AND LEAF RESPIRATION.
       Results: Instantaneous Recycling Index


               -1
                                            FR = 0.485+0.121
               -3
d13CE(o/oo)




               -5

               -7

               -9

              -11
               0.0024   0.0026   0.0028            0.003       0.0032
                                 1/[CO2]E
       Canopy Level Photosynthesis and Respiration in Control
Biomass C      Harvested – Dried – Weighed and Multiplied by the            -736 ± 93.8
               Proportion of Carbon.                                        g/m2

dC             CO2 above canopy (5 m height)                                -8.12 ± 0.37 ‰

DE             Ecosystem Fractionation : (dC- dR)/(1+ dR)                   18.57 ‰

dD             CO2 leaving the canopy- Corrected for
               Photosynthetic Uptake: dD= dR-(DE* ln (1-FR))
                                                                            -3.04 ‰



dDN            CO2 leaving the canopy- Integrated for night and day.        -21.03‰
               Takes into account that at night there is no fractionation
               and possibly additional above ground respiration

PC (FR=0)      =(B.C.*(dB-dR))/(dR-dC+DE) and converted to                  -180.8
               mmoles/m2s                                                   mmoles/m2s
No Recycling

PC (FR>0)      =(B.C.*(dB-dDN))/(dDN-dC+DE) and converted to                -36.1
               mmoles/m2s                                                   mmoles/m2s
Recycling
                          Control (Day)         Treatment (Night)          Control (Night)     Treatment (Day)    Canopy Ht Control    Canopy Ht Treatment


                   6
                                                                            May 30             6
                   5
Height (m)




                   4                                                                           4
                   3
                   2                                                                           2
                   1
                   0                                                                           0
                    300        350        400        450        500         550         600        -15       -5     5           15     25         35
                    6                                                     June 12-13           6
                    5                                                                          5
    Height (m)




                    4                                                                          4
                    3                                                                          3
                    2                                                                          2
                    1                                                                          1
                    0                                                                          0
                     300        350       400         450           500      550         600       -14      -12    -10            -8    -6           -4
                    6                                                          June 24         6
                    5                                                                          5
      Height (m)




                    4                                                                          4
                    3                                                                          3
                    2                                                                          2
                    1                                                                          1
                    0                                                                          0
                     300         350       400        450           500     550         600        -14      -12    -10            -8    -6           -4
                                                [CO2] ppm                                                                δ 13 C
36.1mmoles/m2s

            3.0mmoles/m2s         10.6mmoles/m2s




         7.6
        mmoles/m2s


                     10.6                 10.6
                     mmoles/m2s         mmoles/m2s
Separating Canopy Level Photosynthesis and Respiration
                     from NEE
                  NEE = RC - PC

                  No Recycling

         NEE*dE = (RC*dR) – (PC*(dC – D))

                                            NEE

                      Recycling

      NEE*dE = (RC*(dR-D*ln(1-F))) – (PC*(dC – D))


                                             NEE
              120
                              Gross Photosynthesis
              100             NEE
m moles/m s
         2




              80              Gross Respiration


              60

              40

              20

               0
                    0   0.1   0.2    0.3    0.4       0.5   0.6   0.7   0.8   0.9

                                                  

         Proportion of Above Ground Respiration to Total Night Time
                                Respiration
                                   Growth/Sampling Scheme




              2500

                         Fumigation began
              2000
Height (mm)




              1500
                             Control
              1000           Treatment
                                                                                  Tower
               500                                                           Measurements

                                                       *   *        *    *
                 0
                     0        2        4    6          8       10       12   14
                                                Week

								
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