Understanding Anthropogenic Impact on Peatlands GHGs Dominique Blain, PhD Dominique Blain, PhD IPCC TFI Side Event M Maritim Hotel, Bonn iti H t l B 8 June 2011 Drawing from Quinty and Rochefort, 2003
Page 2 A P A Proposed Approach d A h Measuring GHG fluxes Understanding drivers of GHG dynamics Understanding drivers of GHG dynamics Understanding GHG dynamics in degraded, rewetted and restored peatlands rewetted and restored peatlands Putting it all together
Peatlands are the main wetlands reservoir for soil C. World-wide they contain about 450 Gt C, most in the northern peatlands & about 60 Gt in tropical regions (this number very uncertain). After Strack et al. 2008. Peatlands and Climate Change. International Peat Society, Vapaudenkatu, Jyvaskyla, Finland.
Measuring GHG fluxes in northern peatlands (g C m -2 yr -2 ) Page 4 78 ± 59 NEE = GPP - R e 413 ± 92 R e - Ecosystem Respiration R E t R i ti GPP – Gross primary productivity (CO 2 ) 8 ± 7 Plant respiration Soil respiration 491 ± 130 491 ± 130 (CO 2 ) ( 2 ) (CO 2 ) ( 2 ) Methane flux (CH 4 ) vascular plants moss methane oxidation water table water table methanogenesis Peat/soil 20 ± 12 NEP = - NEE Blain & Lafleur, 2010
Page 5 Compilation of annual measured C budgets for peatland sites peatland sites C = CO 2 -C + CH 4 -C + DOC + C ppt 300 Worrel et al. (2003) 250 Roulet et al.( 2007) in C ga m -2 yr -1 ) Nilsson et al. (2008) 200 Dinsmore et al. (2010) 150 Flanagan et al. (2010) flux (g C L Lund (2009) d (2009) 100 Jac.-Kor. (2009) 50 C 0 0 C loss -50 -100 100 NEP CH4 DOC Precip Total C
Understanding drivers of Net Ecosystem Exchange Page 6 • LAI and pH affect both GPP and NEE • GPP more variable than R e GPP i bl th R • Overall: peatland type not a good predictor of NEE After Lafleur, 2009
Page 7 Understanding Controls over CH4 emissions • CH4 emissions highly variable CH4 emissions highly variable • Winter emissions contributing about 10% of the annual emissions • Spatial ‘hotspots’ Lafleur, 2009 1000 B Fort Simpson NWT Schefferville QC Thompson MB Clay Belt ON Finland S. Hudson Bay Lowland Churchill, MN Schefferville QC WTD a key factor in CH 4 emissions Dorset ON Kejimkujik NS 4 Riviere du Loup QC Riviere du Loup QC Shippagan NB Shippagan NB Mer Bleue ON Radisson QC (depth of oxic and anoxic parts of the ux (mg m -2 d -1 ) 100 peat) Different intercepts : mean or base rate p 10 10 Average CH 4 fl of CH 4 emission controlled by other factors (vegetation, mean climate, etc.) Mer Bleue 1 after Moore TR, unpub. , p 0.1 -60 -50 -40 -30 -20 -10 0 Average water table position (cm)
Page 8 Carbon is also lost in dissolved form: DOC losses from peatlands range from <5 to 40 g C m -2 yr -1 DOC as a percent of NEP range averages from 5% to 70%; DOC as a percent of NEP range averages from 5% to 70%; in individual years it can be >100% DOC export is controlled by 1) production in the peat profile and 2) discharge ( Q ): • variations in flux at a given peatland are largely determined by Q • differences among peatlands in similar hydrologic settings are production related
Page 9 Peatlands Drainage: what happens NEE = GPP - R e R e - Ecosystem Respiration GPP GPP – Gross primary G i productivity (CO 2 ) Plant respiration Soil respiration (CO 2 ) (CO 2 ) Methane flux Methane flux (CH 4 ) vascular plants moss methane Acrotelm oxidation water table methanogenesis Peat/soil Catotelm Strack and Waddington, 2007 NEP = - NEE
Intensity of post-drainage utilization varies Page 10 I t Intensive forestry i f t Pasture Cropping Peat extraction
Degraded peatlands: losses of functions Page 11 Non-functional acrotelm: Loss of peat hydraulic properties Price and Whitehead, 2004 Erratic water table regime : drying and rewetting episodes McNeil and Waddington, 2003 Persistent source of CO2 fluxes t to atmosphere (100% - 400% of t h (100% 400% f pristine) Waddington et al., 2002 Little re-colonization by Sphagnum mosses Waddington et al Waddington et al., 2008 2008 Quinty and Rochefort, 2003
Page 12 A peatland may not restore on its own ‘Natural’ recolonization of degraded peatlands is slow, and vegetation establishment dominated by vascular vegetation (herbs and shrubs), with poor moss colonization (herbs and shrubs) with poor moss colonization Poulin et al., 2005 Waddington et al., 2008 Rewetting reduces R e but does not stabilize WT fluctuations if functional moss layer is missing f ti l l i i i Waddington and Day, 2007 Restoring C sink function involves water table regulation by Restoring C sink function involves water table regulation by living moss layer (acrotelm) Post-mining restoration techniques have been developed and fi ld t field tested: functional acrotelm and C sequestration function t d f ti l t l d C t ti f ti re-established within ~ one decade. Lucchese et al., 2010
Page 13 Contrasting GHG dynamics of Peatlands in different states different states Pristine peatlands : long-term C sequestration and climate cooling effect; R e suppression in anoxic zone; hydraulic properties of moss layer key factor in WTD regulation; climate and vegetation controls on NEE and CH4 Degraded peatlands : drained, with moss layer affected to various degrees by subsidence, compaction, removal. High R e sustained over decades. Re-wetted peatlands : reduction in R e , WT subject to high fluctuations if not regulated (climate sensitive), harsh environment for moss re colonization for moss re-colonization Restored peatlands : C sequestration function re-established through a functional acrotelm.
Page 14 Contrasting GHG dynamics of Peatlands in different States States Pristine Pristine Degraded Degraded Re-wetted Re wetted Restored Restored Intact moss No moss; peat Little or no Re-established Vegetation cover and peat compaction & moss moss layer & peat structure structure subsidence subsidence ctions WTD WTD highly WTD highly WTD and Hydrology fluctuation fluctuating – fluctuating – if acrotelm Func regulated by climate sensitive not regulated fluctuations moss regulated C exchange GEP > R e & R e dominates; g R e smaller; ; GEP R e ; CH 4 GEP>R e ; CH 4 e GEP 0 more variable CH 4 loss larger possibly larger C source to C source to NEP Long-term C g net C sink net C sink atmosphere atmosphere sink
Page 15 Vegetation influences restoration pathway: what are the restoration objectives? what are the restoration objectives? Rehabilitation To re-establish the productivity and some, but not necessarily all, of the plant and animal species thought to be originally present at a site. Ex: re-establish C sink through perennial, vascular vegetation Restoration Re-establishing the presumed structure, productivity and species R t bli hi th d t t d ti it d i diversity that was originally present at a site that has been degraded, damaged or destroyed. In time, the ecological processes and functions of the restored habitat will closely match and functions of the restored habitat will closely match those of the original habitat. Ex: re-establish C sink and hydrological regulation by moss layer Nelleman and Corcoran 2010; FAO 2005.
Page 16 Improved estimation of anthropogenic emissions and removals in peatlands involves: emissions and removals in peatlands involves: Including key elements of C budget: NEE, CH4, DOC Understanding the state of peatlands and h how functions are affected f ti ff t d Determine restoration pathway Determine restoration pathway
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