1 / 30

petagrams Pg = 1x10 15 g

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

amandla
Download Presentation

petagrams Pg = 1x10 15 g

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Global Carbon Model petagrams Pg = 1x1015g 1

  2. 2

  3. 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

  4. 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

  5. SOM Fractionation 5

  6. But are these methods sensitive enough for temporal comparisons????? 6

  7. Decomposition Methods • Litterbags --- weight loss (g) • Density change (g/cm3) • Calculation of k values (year-1) (input/accumulation) • CO2 evolution (g m-2) 7

  8. Decomposition • Litterbags http://www.geog.uu.nl/fg/gapsize/thesis-ovd/Deel10%20Hfd07.pdf 8

  9. 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

  10. Needle/Leaf Litterbags 10

  11. Grass Litterbags 11

  12. Log Decomposition (HJ Andrews) Litterbags??? 12

  13. Root decomposition Litterbags 13

  14. Wood Decomposition density changes g/cm3 14

  15. Decay Constant (k) X = X0 e-kt 100 50 0 % mass remaining Time 15 Olsen 1963

  16. Decay Constant (k) • k = (-ln(wt remaining fraction))/yrs decomp k yr-1 = (-ln(Xt/X0 )) / t yr 16

  17. Examples involving Negative Exponential Decay Curves (Jenny et al 1949, Olson 1963) 17

  18. 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

  19. Examples involving Negative Exponential Decay Curves (Jenny et al 1949, Olson 1963) 19

  20. 20

  21. (C g/m2 yr) 21

  22. 22

  23. So multiple 1st order decay curves may present different k values thru time!! 23

  24. 24

  25. 25

  26. 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

  27. Decomposition usingCO2 Evolution Gilson respirometer Warburg Apparatus 27 http://history.nih.gov/exhibits/stadtman/lab.htm

  28. Decomposition usingCO2 Evolution • Soda lime - Ca(OH)2 (about 75%)   • Weight change • KOH traps • Titration 28

  29. Soil Respiration System (PP System) http://www.ppsystems.com/soil.html 29 Infra-Red Gas Analysis Systems (PP Systems)

  30. 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

More Related