Recent carbon accumulation rates in peatlands along the North Shore of the Gulf of St Lawrence, Canada N.K. Sanderson1*, D.J. Charman1, M. Garneau2 and I.P. Hartley1

1Geography, University of Exeter, EX4 4RJ, UK 2GEOTOP, Université du Québec à Montréal, Canada

*Contact: Nicole Sanderson (nks202@exeter.ac.uk)

1. BACKGROUND

3. SITE DESCRIPTION

4. METHODOLOGY 5. RESULTS AND DISCUSSION

7. WHAT COMES NEXT?

Peatlands are an important component of the global carbon

(C) cycle and have been a net C sink during the Holocene1.

Under current warming conditions, C emissions are

projected to rise due to increased respiration2.

Longer growing seasons and higher rates of C uptake are

also expected3.

Permafrost degradation has been accelerating during the

last 50-100 years4 and is altering peatland hydrology,

microtopography and C cycling.

C stocks have been shown to increase as a result in

Western Canada5,6 and in Arctic and Subarctic Canada7,8;

little is known about many other northern regions.

As peatlands cover 12% of the area of Canada9, changes in

climate-driven peat accumulation could represent an

important future C source or sink.

ACKNOWLEDGEMENTS REFERENCES Thanks to Jean-Pierre Castonguay-Bélanger Julien Minville, Helen Mackay and other field and lab assistants, and also to Les Tourbeux. This project is funded by a University of Exeter (CLES) studentship with support from DECLIQUE. 14C dates from NERC St. Grant NE/I012915/1.

Three peatlands were selected

for this study (Fig. 1):

Located along the North

Shore of the Gulf of St

Lawrence

Formed between 7,400 and

4,200 cal. BP by paludification

on deltaic sands10, 11

Ombrotrophic peatlands, i.e.

only inputs from precipitation

Dominated by Sphagnum

moss, ericaceous plants and

shrubs; lichens become more

dominant further North

Microform distribution and

pool morphology vary

Peat monoliths (N = 30, max. depth 1 m) were extracted from the

central dome of each peatland using a box corer (Table 1; Fig. 2).

To calculate carbon accumulation rates (CAR):

Carbon content: calculated using bulk density and loss on ignition13

(3 cm3, 0.5 cm); C content assumed to be 50% organic matter14.

6. PRELIMINARY CONCLUSIONS

Additional funding by the CCSF (2012/13) Thanks to the Maple Leaf Trust and the Canadian Women’s Club, London

Region A B C D

Baie Comeau 3 3 3 -

Havre-Saint-Pierre 3 3 3 3

Blanc Sablon 3 3 - 3

< Table 1. Distribution of cores taken by microform (N = 30) A: hollow/pool edge B: lawn C: Sphagnum hummock D: lichen hummock

Water table

Pool PEAT < Figure 2. Peat cross-section with microform distribution along a wetness (proximity to water table) gradient

Chronology: established by

lead-210 (210Pb) dating15 all

cores using α-spectrometry

(method modified from 16) and

the CRS model17 assuming a

constant rate of supply.

Preliminary age models were

constructed using 14C dates for

2 cores in CLAM version 2.218. Left: 210Pb plating procedure; Right: alpha counter and 209Po/210Po spectra

Completing Blanc Sablon profiles to improve understanding of

carbon accumulation in permafrost

Improving age models: combination of tephra and additional 14C

dates for longer-term CAR between sites for the last millennium

(Medieval Climate Anomaly/Little Ice Age).

Water table depth reconstructions: multi-proxy analysis (testate

amoebae and plant macrofossils) to investigate climate-C

dynamics link between sites.

Carbon accumulation rates for the last millennium decreased

during the transition between the warm MCA and the cool LIA.

Within sites, microforms accumulate peat at different rates.

This high degree of replication in this study allows for separation

of allogenic (climate) vs. autogenic (peatland-specific) signals,

i.e. what role do local drainage, exposure and snow cover play?

Further work is needed to investigate the drivers of these

changes in carbon accumulation, and to work on up-scaling.

1. To compare regional changes in carbon accumulation

rates (CAR) between peatlands located in three distinct

ecoclimatic regions during the last millennium;

2. To evaluate within-site variability in CAR trends along a

microtopography gradient for the 20th century.

2. OBJECTIVES

1Yu, Z.C. (2011) Holocene 21, 761-774; 2Dorrepaal, E. et al. (2009) Nature 460, 616-619; 3Charman, D.J. et al. (2013) Biogeosciences 10, 929-944; 4Payette, S. et al. (2004) Geophys. Res. Lett. 31, L18208; 5Turetsky, M.R. et al. (2002) Soil Biol. Biochem. 34, 907-912; 6Vitt, D.H. et al. (2000) Can. J. For. Res. 30, 283-287; 7Lamarre, A. et al. (2013) Rev. Palaeobot. Palyno. 186, 131-144; 8Vardy, S.R. et al. (2000) Holocene 10, 273-280; 9Tarnocai, C. (2006) Global Planet. Change 53, 222-232; 10Magnan, G. (2013) Ph.D. Thesis. Université du Québec à Montréal, Canada; 11Dionne, J-C. and P.J.H. Richard (2006) Géo. Phys. Quat. 60, 199-205; 12Payette, S. (2001) In S. Payette and L. Rochefort (Eds.), Écologie des Tourbières du Québec-Labrador, Les Presses de l’Université Laval, Saint-Nicholas, Canada, p.199; 13Dean, W.E.J. (1974) J. Sed. Petrol. 44, 242-248; 14Turunen, J. et al. (2002) Holocene 12, 69-80; 15Turetsky, M.R. (2004) Wetlands 24, 324-356; 16Ali, A. et al. (2008) Appl. Radiat. Isotopes 66, 1350-1358; 17Appleby, P.G. and F. Oldfield (1978) Catena 5, 1-8; 18Blaauw, M. (2010) Quat. Geochronol. 5, 512-518

South (Estuary) No permafrost

North (Gulf) Permafrost

0

100

200

300

400

500

600

0-5 5-10 10-50 50-100

0

100

200

300

400

500

600

0-5 5-10 10-50 50-100

0

100

200

300

400

500

600

0-5 5-10 10-50 50-100

BAIE COMEAU HAVRE-SAINT-PIERRE BLANC SABLON

No. Years No. Years No. Years

CA

R (

g C

m-2

a-1

)

0

10

20

30

40

1700-1850 1400-1700 1250-1400 1166-1250

BC

HP

End MCA LIA

Years (AD)

CA

R (

g C

m-2

a-1

)

^ Figure 3. Carbon accumulation rates for the last 100 years for the three peatland regions located along a N-S, climate, oceanicity and permafrost gradient.

For each region, 3 replicate cores were taken along a microtopography gradient, where the colours refer to microforms as outlined in Section 4:

A (hollow); B (lawn); C (Sphagnum hummock) and D (lichen hummock).

Ages were calculated using 210Pb dates; the number of years refers to the time before collection (2011-2013). Error bars indicate standard deviation.

< Figure 4. Carbon accumulation rates (CAR) for 2 lawn cores from each Baie Comeau and Havre-Saint-Pierre, calculated with available 14C dates covering the end of the warmer Medieval Climate Anomaly (MCA, red) and cool Little Ice Age (LIA, blue)

Blanc Sablon (BS)

Palsa peatland

Tundra forest ecozone

Peat depth: 1.5-2 m

MAT: 0.2 ± 1.1 oC

MAP: 1067 mm a-1

Coordinates: 51o27’ N 57o11’ W

Domed peatland

Closed boreal forest ecozone

Peat depth: 4-6 m

MAT: 1.5 ± 0.9 oC

MAP: 1014 mm a-1

Coordinates: 49o08’ N 68o12’ W

Baie Comeau (BC) Havre-Saint-Pierre (HP)

Plateau peatland

Open boreal forest ecozone

Peat depth: 2-3 m

MAT: 1.1 ± 2.0 oC

MAP: 1080 mm a-1

Coordinates: 50o17’ N 64o47’ W

< Figure 1. Study sites along the North Shore of the Gulf of St Lawrence. Permafrost regions12:

(1) no history of permafrost;

(2) sporadic permafrost zone (< 2% cover);

(3) discontinuous permafrost zone (< 50% cover)

© Wikipedia (2013)

Gulf of St Lawrence

3 2

1

N

Within-site variability (Objective 1, Fig. 3):

Recent C accumulation rates calculated for the last 100 years.

For all sites, CAR is highest for the last 5-10 years as acrotelm peat

is not yet fully decomposed. BC has the highest rates overall.

Within each site, Sphagnum hummocks have the highest CAR, and

lichen hummocks the lowest. Note that CAR for BS are likely

overestimated: lower resolution 210Pb profiles?

While CAR for wet (hollow) and intermediate (lawn) microforms

are similar, C emissions are likely higher for hollows20.

Between-site (regional) variability (Objective 2, Fig. 4):

C accumulation rates for the last millennium.

Overall, CAR are higher at BC.

At both sites, CAR lowest during and since the Little Ice Age (LIA).

A slight increase in CAR at HP since the LIA may be due to the

presence of more rapidly accumulating Sphagnum hummocks

under changing hydrological: permafrost melt, climate warming,

and/or other factors?

Mean annual temperature (MAT) and precipitation (MAP) data from 1971-2000 Climate Normals: http://climate.weather.gc.ca/climate_normals/index_e.html (Accessed 23.10.13)