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Global Carbon Model. petagrams Pg = 1x10 15 g. 1. 2. Soil Ecology. the process whereby organic material is broken down into its smaller molecules

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Presentation Transcript
slide1

Global Carbon Model

petagrams

Pg = 1x1015g

1

soil ecology

Soil Ecology

  • the process whereby organic material is broken down into its smaller molecules
  • biological, physical, and chemical breakdown of organic matter resulting in humus formation, release of CO2, H2O, and nutrients

Decomposition

Methods ??

3

soil organic matter som methods
Soil Organic Matter (SOM) Methods
  • LOI– loss on ignition
  • Wet Oxidation–eg, Walkley-Black (determining C by titration of unreduced dichromate)
  • Dry Combustion– eg, LECO (Infrared & OC&Inorg C)
  • Fractionation

4

decomposition methods
Decomposition Methods
  • Litterbags --- weight loss (g)
  • Density change (g/cm3)
  • Calculation of k values (year-1) (input/accumulation)
  • CO2 evolution (g m-2)

7

decomposition
Decomposition
  • Litterbags

http://www.geog.uu.nl/fg/gapsize/thesis-ovd/Deel10%20Hfd07.pdf

8

decomposition1
Decomposition
  • Litterbags
    • Different mesh sizes
    • Different times
    • Different substrates (pure/mix)
    • Standards?

http://www.geog.uu.nl/fg/gapsize/thesis-ovd/Deel10%20Hfd07.pdf

9

slide12

Log Decomposition

(HJ Andrews)

Litterbags???

12

slide14

Wood Decomposition

density changes

g/cm3

14

slide15

Decay Constant (k)

X = X0 e-kt

100

50

0

%

mass

remaining

Time

15

Olsen 1963

decay constant k
Decay Constant (k)
  • k = (-ln(wt remaining fraction))/yrs decomp

k yr-1 = (-ln(Xt/X0 )) / t yr

16

decomposition time
Decomposition Time
  • Mean Residence Time (MRT) steady state

Forest Floor Biomass/Annual Litterfall = ? Year

  • Half-Life (50% remaining)

k = (-ln(Xt/X0 )) / t years

t(1/2) = -ln 0.5/k = 0.693/k

  • 1% remaining (~MRT)

t(.01 ) = -ln 0.01/k = 4.605/k

kg / kg year-1 = year

18

the carbon balance

Net Ecosystem

Carbon Exchange

Gross Photosynthesis

Dark and

Photo

Respiration

CO2 Storage

bole respiration

litter

respiration

microbial

respiration

root respiration

The Carbon Balance

http://www.vaisala.com/DynaGen_Attachments/Att32668/GMP343%20Introduction.pps#6

26

slide27

Decomposition usingCO2 Evolution

Gilson respirometer

Warburg Apparatus

27

http://history.nih.gov/exhibits/stadtman/lab.htm

slide28

Decomposition usingCO2 Evolution

  • Soda lime - Ca(OH)2 (about 75%)  
    • Weight change
  • KOH traps
    • Titration

28

soil respiration system pp system
Soil Respiration System (PP System)

http://www.ppsystems.com/soil.html

29

Infra-Red Gas Analysis Systems (PP Systems)

century model variables predicting som accumulation
Century Model - variables predicting SOM accumulation
  • Amount above- & belowground plant material to decay
  • Chemical quality of material added to detritus (e.g. lignin, N)
  • Soil texture
  • Climate

30

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