1. Forest Soils & Site Productivity Soil Organic Matter and Organisms 1

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4. Soil Carbon Inputs – Outputs = Residual Inputs: ? plants (litterfall, roots, exudates), microorganisms, animals, atmosphere (dust, wind, ppt, etc), erosion deposition, humans (mulching, biosolids, etc), ??? Outputs: ? leaching, decomposition/respiration (microbes/invertebrates, etc), uptake, erosion, fires, humans (plowing, bulldozing, digging, harvesting, etc), ??? 4

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6. Organic Matter Surface residues/Forest Floor/O horizons –Not universally considered as part of SOM but as O horizon it may be included as OM of the soil. Soil Organic Matter (SOM). Component of the <2 mm fraction. 6

7. A Soil Profile in Iceland 7

8. Larix sibirica 8

9. Betula pubescens 9

10. Pinus contorta 10

11. Iceland research study, 2000 11

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13. Leachates from Larch, Birch, and Lodgepole Pine Ecosystems 13

14. Pseudotsuga menziesii Soil Organic Matter (Mg/ha) 14

15. Some Organic Compounds in the Soil 1.Carbohydrates –a) sugars – pentoses & hexoses (eg, glucose – C 6 H 12 O 6 ) –b) starches – glucose chains –c) hemicellulose – polysaccharides, H 2 0 insoluble –d) cellulose – glucose long-chain polymers (most abundant in plant) 15

16. Some Organic Compounds in the Soil 2.Proteins – small C-chains, combination of amino acids – C, H, N & some O & S 3.Lignin – complex polymer of aromatic nature 4.Fats, oils, waxes, resins – complex carbohydrates, H 2 0 insoluble 5.Chitin – polysaccharide exoskeletons of insects & also in walls of many fungi 6.Humus – amorphous, dark colored, colloidal organic material 16

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19. Mechanisms of Soil Organic Matter Stabilization 19

20. Predicted Organic Matter fractions and turnover times in the unmanured plot of the Broadbalk experiment, Rothamsted. Annual input of C = 1.2 Mg ha -1. FractionAmt of Carbon (Mg ha -1 ) Turnover time (years) Readily decomposed plant tissue 0.10.2 Resistant plant tissue0.63.3 Microbial biomass0.32.4 Physically protected OM13.671 Chemically stabilized OM14.62900 20

21. SOM - where in the SOIL???? Depth (cm) 0 10 20 30 40 50 60 %Carbon 123456 21

22. AridisolMollisolAlfisolSpodosol Soil Order ?? 22

23. AridisolMollisolAlfisolSpodosol Mollisol plowed 23