24. How to model water table? Mature spruce bog humic layer fibrous layer humic layer fibrous layer years Young spruce bog water table depth water table depth Hypothesis: Constant from surface (Clymo 1984) bedrock mineral soil bedrock mineral soil Strong positive feedback (paludification) humic layer fibrous layer water table depth
25. How to model water table? Mature spruce bog humic layer fibrous layer humic layer fibrous layer years Young spruce bog water table height Constant from bedrock Strong negative feedback water table height bedrock mineral soil bedrock mineral soil Null hypothesis
26. How to model water table? null? ? fibrous layer Mature spruce bog humic layer humic layer fibrous layer years Young spruce bog Which hypothesis ? Somewhere in between Needs for mechanistic simulation! water balance soil properties bedrock mineral soil bedrock mineral soil
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29. Fibrous Humic Decomposition temperature dependence moisture dependence Frolking et al. 2002 bedrock mineral soil Td Md Biogeochemical model
30. 2 simulations Fibrous Humic Dynamic peat depth model Static model (mineral soil model) Equilibrium SOC: self-regulatory Equilibrium SOC: sensitive to initialization bedrock mineral soil
34. Results Comparison: BOREAS NOBS, 2003 (Dunn, Barford, Wofsy, Goulden, & Daube 2007) water table depth [m] soil temperature [ °C ] Julian day
35. Climate change: equilibrium 40% loss Extrapolate over northern peatlands, 72-182 PgC 34-87 ppm year soil organic carbon [kgC m -2 ]
36. Climate change: transient HadCM3 SRES A2 at 2099 + 4.3 °C + 42.1 mm ~10% loss Extrapolate over northern peatlands, 18-46 PgC 9-22 ppm year soil organic carbon [kgC m -2 ]
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40. メタン Global mean radiative forcing Wetlands: 72% of natural source (Prather et al. 1995)
46. 泥炭地の未来 ? boreal temperate 4°C rise: Can cross the threshold? Global Soil Data Task (2000) New et al. (2000) piecewise 90-percentile quantile regression
47. 泥炭地の未来 ? http://maps.google.com http://dustydavis.com/ http://www.canada.com Prince Albert (MAT 0.7°C) Bismarck, ND (MAT 5.6°C)