Evolution of wetlands since the Last Glacial Maximum
Pirita Oksanen University of Bristol
• Wetland synthesis - distribution, extent, type and accumulation
• Public database• Maps• Data – model comparisons• Since ca. 21 000 BP• Phase 1. Northern extratropics.• Phase 2. Tropics.
• 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 • 400-500 Gt C in peat• 100-150 Tg CH4/a from natural wetlands• ca. 40 Tg CH4/a from rice paddies• estimates for the LGM 80-110 Tg CH4/a
• 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 (137-399)• Floodplains – 100 (50-200)• Lakes – 43 (17-89)• Rice paddies – 310 (179-438)
~INLAND WETLANDS~
BOGS
SWAMPS
FENS
OPEN WETLANDS
MARSHES
SPRINGS GEOTHERMAL WETLANDSFLUVIAL
LACUSTRINE
Open WoodedRaised Blanket
Aapa
Rich Oligotrophic
Eutrophic Mesotrophic
Wooded
Paludifying forestSwamp forest Cloud forest
Raised Rich
Open
Eutrophic Mesotrophic
Shrub-swamp
Shrub-marshCarr Alder thicket
Palsa mirePolygonal mire
Wet tundra
High palsa mire Plateau palsa mire
Sloping mire
Wet meadow
Saline/brackish AlkalineFreshwater
Flooded meadow Sedge marsh
Terrestrialising lake
~COASTAL/MARINE WETLANDS~
INTERTIDAL MARSHES INTERTIDAL SWAMPS
AQUATIC BEDSINTERTIDAL FLATS
Salt marsh Salt meadow SaltingRaised FreshwaterBrackish
Mangrove Nipah
Tidal freshwater swamp forest
~HUMAN-MADE WETLANDS~
AGRICULTURAL
ARTIFICIAL LAKES
CANALSEXCAVATIONS
Rice field Wet meadow
Pond Reservoir
Wastewater treatment
Thermokarst lake
Wet moor
Oligotrophic
Alpine wet meadow
~NOT WETLAND~DRIED PEATLAND BURIED PEATLAND
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
Mires today, sites with bottom dates
Previous databases used: Oksanen 2005, Gorham et al. 2005, McDonald et al. 2006, PAIN.
Lappalainen et al. 1996
Basal peat dates 50 000 – 21 000 BP
Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon
Mires at 13000 BP
Experimental ice-sheet data by W.R Peltier, University of Toronto
Mires
at 11000 BP
Mires at 10000 BP
Mires
at 9000 BP
Mires at 6000 BP, sites with basal peat dates
Continental and ice-sheet outlines by Patrick Bartlein, University of Oregon
Mire initiation in arctic/boreal regions
0
50
100
150
200
250
300
350
400
450
mire initiation casescumulative/ 5
0 2000 5000 8000 11000 15000 >21000