Post on 30-Apr-2018
transcript
Greenhouse Gas Emissions from Tropical Peatlands: Biogeochemical Processes and
Mitigation Strategies
An ESI Seed Grant Project2015-2017
Carbon Cycling inTropical Peatlands
Alison Hoyt, Alex Cobb, Laure Gandois, Xiaolei Liu, Shane O Reilly, Guangchao Zhuang, Roger Summons, David VanInsberghe, Martin Polz, Shuhei Ono, Benjamin Kocar,
Sunitha Pangala, Estelle Chaussard, Charles Harvey
(Hooijer et al, 2010)
Huge C fluxes – large uncertainties!
Range of annual emissions from tropical peat :
637 – 2255 Mt/y CO2
2-7% of 2011 global emissions
Overview:
Background:• What is peat? Why does it accumulate?• Current trends – deforestation & drainage• Local impacts: fire, flooding• Global impacts: GHG emissions
CO2 Fluxes:• Why do drained peatlands release CO2 to the atmosphere?
Methane (CH4) Cycle:• Do tropical peatlands produce more CH4 than we realize?• If so, how is it transported? Where is it oxidized?
(Posa et al, 2011)
Borneo
Peatlands of Southeast Asia
Peat areas shown in black
Deforestation in Borneo
(Hugo Ahlenius, UNEP/GRID-Arendal)
View into the canopy of a tropical peat swamp forest
Cross-section of peat below the surface, cut for road construction
Why do drained peatlands
release CO2 to the atmosphere?
Why does peat accumulate?Saturated soils -> Anaerobic conditions ->
Slow decomposition -> Organic matter accumulation
Carbon accumulates over thousands of years
Draining peatlands releases sequestered carbon as peat decomposes
Natural peat dome hydrologyThe water table is close to the surface everywhereDecomposition is slow, peat accumulates
This lowers the water table -> Creates aerobic conditions -> Faster decomposition -> Peat oxidation ->Result: Subsidence + CO2 emissions
Peatlands are drained by adding canals
Peat subsidence in Johor, Malaysia
(Deltares)
Drainage and peat oxidation lead to subsidence
NASA Image by Jeff Schmaltz,2006
Peat fires burn long-term carbon stocks
Do tropical peatlands produce more CH4 than we realize?If so, how is it transported? Where is it oxidized?
CH4 Fluxes
Methanogenesis
Diffusion
Measured CH4 emissions from tropical peat swamp forests are unexpectedly low
These measurements focus on measuring the surface flux, which only captures diffusion and ebullition
Ebullition
Methanogenesis
Tree Transport
Aerobic Oxidation
Diffusion
Anaerobic Oxidation
Lateral Transport
Do tropical peatlands produce more CH4 than we realize?
Other pathways are playing a much more important role!Much of the CH4 produced is transported laterally, and then oxidized in rivers
Alex CobbSunitha PangalaLaure Gandois
René DommainHa NguyenLucy Hutyra
Khalish IderisAmy Chua
Kai Fuu MingXiaomei Xu
Vincent GauciEd HornibrookCharles Harvey
Xiaolei LiuLiz Corbett
Jeff ChantonEstelle Chaussard
Sandra SeppalainenHajah Jamilah
Joffre bin AhmadKamariah Abu Salim
Mahmud YusoffJoffre bin AhmadJangarun ak Eri
Pudek ak ZulkifleeNur Salihah Haji Su’ut
Acknowledgements