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Evolution of wetlands since the Last Glacial Maximum Pirita Oksanen University of Bristol.

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Presentation on theme: "Evolution of wetlands since the Last Glacial Maximum Pirita Oksanen University of Bristol."— Presentation transcript:

1 Evolution of wetlands since the Last Glacial Maximum Pirita Oksanen University of Bristol

2 Wetland synthesis - distribution, extent, type and accumulation Public database Maps Data – model comparisons Since ca BP Phase 1. Northern extratropics. Phase 2. Tropics.

3 Peatlands net sink of CO2 – vegetation sequesters from the atmosphere Wetlands net source of CH4 – methanogenesis in waterlogged environment ca. 5 million km2 natural wetlands over 1 million km2 irrigated cultivation Gt C in peat Tg CH4/a from natural wetlands ca. 40 Tg CH4/a from rice paddies estimates for the LGM Tg CH4/a

4 temperature, water table and vegetation control CH4 production and flux wide variation of CH4 fluxes both between and within wetlands and seasons Mean values (Aselmann & Crutzen -89) Bogs – 15 (1-50) CH4/m2/day Fens – 80 (28-216) Swamps – 84 (57-112) Marshes – 253 ( ) Floodplains – 100 (50-200) Lakes – 43 (17-89) Rice paddies – 310 ( )

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6 Wetland vegetation plant functional types OPEN mosses with dwarf-shrubs and forbs – bogs and fens tall sedges and grasses (>1.5 m height) - fens and marshes low sedges and grasses - fens and other open wetlands open water WOODED (>5% tree cover) - bogs and fens wooded, evergreen broad-leaved wooded, evergreen needle-leaved wooded, seasonal broad-leaved wooded, seasonal needle-leaved FORESTED (>40% tree cover) - swamps forested, evergreen broad-leaved forested, evergreen needle-leaved forested, seasonal broad-leaved forested, seasonal needle-leaved

7 Mires today, sites with bottom dates Previous databases used: Oksanen 2005, Gorham et al. 2005, McDonald et al. 2006, PAIN. Lappalainen et al. 1996

8 Basal peat dates – BP Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon

9 Mires at BP Experimental ice-sheet data by W.R Peltier, University of Toronto

10 Mires at BP

11 Mires at BP

12 Mires at 9000 BP

13 Mires at 6000 BP, sites with basal peat dates Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon

14 Mire initiation in arctic/boreal regions >21000


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