Talk by John Couwenberg at VNN peatland meeting, Leeds 18th January 2012

1. Assessing GHG Emissions from peatlands
using vegetation as a proxy
John Couwenberg

2. Peatlands contain a lot of carbon
Tollund Man, Denmark

3. drainage mobilises carbon: CO2 (und N2O) emissions
Kalimantan, Indonesia

4. rewetting to reduce emissions
Peenetal, Germany

5. Quantifying GHG fluxes:
• direct flux measurements (chambers, micrometeorol.)
– combined with indicators / proxies (cf. IPCC)
• CO2 flux also assessed via stock-change approach
– standard approach for e.g. forest, mineral soil)
– not practicable for organic soils
organic soil fluxes are based on direct measurement

6. Measuring over small areas: closed chamber method

7. For all three GHG (CH4, CO2, N2O)

8. Measuring over large areas: eddy covariance

9. Mainly used for CO2, but also for CH4 and N2O

10. Measurements need to be frequent, long term, intensive

11. Wide variety of site parameters influencing emissions
…peatland types, peat types, spatial heterogeneity,
land use, former land use, abiotic conditions, vegetation…

12. Measuring is complicated, time consuming, expensive

13. Measure pilot sites, develop proxies
Meta-analysis: water level main single explanatory variable

14. CO2 emissions from temperate European peatlands
Field measurements: WL is a good proxy
70
60
t CO2·ha-1·y-1
50
40
30
20
10
r2 = 0.68, p < 0.01
0
-10
-140 -120 -100 -80 -60 -40 -20 0 20 40
mean annual water level (cm)
after Couwenberg et al. (2011)

15. CO2 emissions from temperate European peatlands
Subsidence based emissions: WL is a good proxy
70
60
t CO2·ha-1·y-1
50
40
30
20
10
r2 = 0.68, p < 0.01
0
-10
-140 -120 -100 -80 -60 -40 -20 0 20 40
mean annual water level (cm)
after Couwenberg et al. (2011): ● direct flux, ● site specific subsidence

16. N2O emissions from temperate European peatlands
Direct flux measurements: WL is a good proxy
100
80
kg N2O·ha-1·y-1
60
40
20
0
-100 -80 -60 -40 -20 0 20 40 60
mean annual water level (cm)
Couwenberg et al. (2011), bog sites, fen sites without fertilizer application, fen sites with fertilizer
application; x treed sites.

17. CH4 emissions from temperate European peatlands
Direct flux measurements (annual flux): WL is a good proxy
600
500
400
kg CH4·ha-1·y-1
300
200
100
0
-100 -80 -60 -40 -20 0 20 40
mean annual water level (cm)
Couwenberg et al. (2011)

18. CH4 emissions from tropical and boreal peatlands
Direct flux measurements (hourly flux): WL is a good proxy
3
CH4 emission [mg m-2 h-1]
15
-0,5
2 10
wood peat SE Asia
1 5
0 0
-100 -80 -60 -40 -20 0 20 -100 -80 -60 -40 -20 0 20
water level [cm]
Couwenberg et al. (2010)
Tropical; Temperate; ∆ Boreal

19. Proxy: Water level
• many and frequent data necessary
• measure a lot (e.g. automatic logger)
• modeling using weather data (calibrate, monitor)
• WL not yet measurable using remote sensing
• particularly for CH4 high uncertainty remains

20. CH4 emissions from temperate European peatlands
WL is not a quantitatively precise proxy
600
500
400
kg CH4·ha-1·y-1
300
200
100
0
-100 -80 -60 -40 -20 0 20 40
mean annual water level (cm)
Couwenberg et al. (2011)

21. CH4 emissions from temperate European peatlands
Direct flux measurements (annual flux): WL + vegetation
600
500
r2 = 0.76, p < 0.01
400
kg CH4·ha-1·y-1
300
200
100
0
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0
mean annual water level (cm)
Couwenberg et al. (2011), sites with aerenchymous shunt species; sites with open vegetation without
shunt species; x treed sites.

22. CH4 emissions from temperate European peatlands
Direct flux measurements (annual flux): vegetation
800
700
600
kg CH4·ha-1·y-1
500
400
300
200
100
0
0 500 1000 1500 2000 2500
aerenchymous leaves (n m-2)
After Drösler (2005)

23. Emissions strongly related to water level
Vegetation strongly related to water level
Emissions also related to vegetation
 Use vegetation as indicator for emissions!

24. Vegetation as indicator of emissions
• Integration of site parameters
• Quick
• Easy
• Cheap
• Reliable … ?
Greenhouse Gas Emission Site Types (GESTs)

25. Proxy: Vegetation
advantages
• relationship to long-term water level
• relationship to other relevant site conditions
(nutrient status, pH, land use, …)
• influences fluxes itself
(substrate quality, aerenchyma)
• can be mapped on relevant scale (1:2,500 – 1:10,000)
• can be mapped using remote sensing (good for €)

26. Proxy: Vegetation
disadvantages
• slow reaction to changing site conditions
• must be calibrated for different climate and
phytogeographic regions
• not suitable when not there (e.g. ‘black deserts’)

27. Towards GESTs: Vegetation-forms
Integration of flora and environment
- Species groups
- Presence and absence as indicator
site factor gradient
species groups
site factor classes 1 2 3 4 5
subunits 1 2 1 2

28. Water level classes (Wasserstufen)
Water level class long-term median water level (cm)
wet season dry season
7+ upper sublitoral +250 to +140 +250 to +140
6+ lower eulitoral +150 to +10 +140 to +0
5+ wet (upper eulitoral) +10 to -5 +0 to -10
4+ very moist -5 to -15 -10 to -20
3+ moist -15 to -35 -20 to -45
2+ moderately moist -35 to -70 -45 to -85
2- moderately dry Water supply deficiency: < 60 l/m²
3- dry Water supply deficiency: 60–100 l/m²
4- very dry Water supply deficiency: 100–140 l/m²
5- extremely dry Water supply deficiency: > 140 l/m²

29. GESTs:
Greenhouse gas Emission Site Types

30. Assessing rewetting
• N2O fluxes from drained peatlands very erratic
• N2O fluxes from rewetted peatlands negligible
• N2O fluxes can only decline upon rewetting
• reduction cannot be quantified
• disregard N2O: conservative estimate of reductions

31. Ostrovskoje: GESTs
A: 2009
B: 2039 Baseline
C: 2039 Wiedervernässung
A: 7343 t CO2-eq / J
B: 7933 t CO2-eq / J
C: 3779 t CO2-eq / J

32. Rewetting
• hydrologic analysis necessary:
which sub-area will become how wet ?
• CH4 emissions may become very high
• but unlikely higher than previous CO2 emissions

33. Complication: methane spike after rewetting
plants not adapted to wet conditions will die off
 labile carbon pool  anoxic conditions  methane
direct flux measurements rare or lacking
avoid: remove plants, possibly even enriched upper soil

34. Complication: nutrient enriched soils
Large methane fluxes may persist (how long ?)
2005 2006 2007
kg CH4 ha-1 a-1 2521 4934 2376
additional problem: litter import
Augustin & Chojnicki, 2008

35. Peatlands contain a lot of carbon
Tollund Man, Denmark

36. peatlands are much more than just carbon…
• biodiversity
• water retention
• nutrient retention
• local cooling
• tourism
• production (paludicultures)
 avoid one-dimensional approach to rewetting

37. and make it wet !