Long-term and recent ecohydrological dynamics of patterned peatlands in north-central Quebec (Canada)

Abstract

Peatlands are natural ecosystems that provide archives of the hydrological cycle, ecological processes and terrestrial carbon dynamics. In the north-central region of Quebec (eastern Canada), patterned peatlands developed in topographic depressions of the Precambrian Shield following the Laurentide Ice Sheet retreat. These peatlands display characteristics similar to appa mires and other peatlands that developed at the ecotone between the open (taiga) and closed boreal forest biomes of the Northern Hemisphere, and also correspond to the biogeographic limit between ombrotrophic and minerotrophic peatlands. During the Neoglacial cooling period in northeastern Canada, patterned peatlands, mainly oligotrophic fens, registered a hydrological disequilibrium expressed by an increase in surface wetness as aquatic microforms expanded to the detriment of terrestrial surfaces. Ecohydrological trajectories were reconstructed from a detailed study of two patterned peatlands in order to document their sensitivity to climate variations. To do this, plant macrofossil and testate amoeba data were combined with peat carbon accumulation rates, C:N ratios, ²¹⁰Pb and ¹⁴C chronologies. Data show that peatlands initiated ca 6500 cal. y BP as ombrotrophic or minerotrophic systems depending on site-specific conditions, followed by a general increase in surface wetness during the Neoglacial cooling until the end of the Little Ice Age. A relatively synchronous ecosystem state shift from oligotrophic to more ombrotrophic conditions was registered at the beginning of the 20th century in central and lateral cores of both study sites, evoking the likely influence of recent warming on peat accumulation. These results suggest a potential northward migration of the biogeographic limit of the ombrotrophic peatland distribution during the 20th century, which could have implications for the role of these ecosystems as C sinks at the continental scale. Overall, these peatlands have stored a mean carbon mass of ca 100 kg m^{− ²}.

Keywords

Climate change ecosystem state shift Neoglacial cooling patterned fens plant macrofossils recent peat accumulation testate amoeba

Introduction

Peatlands in Canada cover ~13% of the land area and are mainly concentrated in the boreal and subarctic regions (Tarnocai et al., 2011). They have accumulated approximately 150 Gt C (Gorham et al., 2007; Tarnocai et al., 2005) of which 10.5 Gt C are stored in northern Quebec (Garneau and van Bellen, 2016). Ombrotrophic and minerotrophic peatlands are distributed along a latitudinal gradient corresponding to climatic variables (temperature and precipitation) that influence their development and ecology (Belyea, 2007; Yu et al., 2009). In subarctic regions, where cooler climate conditions limit Sphagnum growth and promote surface runoff, patterned fens similar to appa mires are the most common peatlands (Foster and Fritz, 1987; Payette, 2001; Rydin and Jeglum, 2013; Seppälä and Koutaniemi, 1985). In Quebec and Labrador, these patterned fens are characterized by a surface microtopography with alternating ridge (low hummock) and pool compartments oriented perpendicularly to the slope (Foster and King, 1984; Payette, 2001; Seppälä and Koutaniemi, 1985) and covering up to 40% of their total surface area (Cliche-Trudeau et al., 2014). The current presence of dead trees as well as apparent string decomposition within several pools suggest a hydrological imbalance defined as “aqualysis” that caused physical degradation of vegetation ridges leading to pool expansion and coalescence (Arlen-Pouliot and Payette, 2015; Cliche-Trudeau et al., 2013; Dissanska et al., 2009; Foster et al., 1983; Tardif et al., 2009; White and Payette, 2016). Previous studies in the La Grande watershed (northeastern Canada) suggested different allogenic and autogenic hypotheses to explain this hydrological disequilibrium. According to van Bellen et al. (2013) and Garneau et al. (2017), the transition to Neoglacial cooler and wetter climatic conditions from ca 3000 cal. y BP (Viau and Gajewski, 2009) was associated with shorter growing seasons that reduced Sphagnum growth and decreased evapotranspiration, leading to the development of pools from the wetter terrestrial microforms. This first episode of pool development was followed by a second episode that corresponded chronologically to the Little Ice Age (ca 1350 and 1850 CE) (van Bellen et al., 2013). Arlen-Pouliot and Payette (2015) attributed the period of pool aggradation to the precipitation increase since the second half of the 18th century. White and Payette (2016) subsequently showed that the physical characteristics of the peatlands (slope, surface area and peat thickness) as well as the size of their watersheds could also influence the hydrological imbalance of these ecosystems. Furthermore, Comas et al. (2011) suggested that the morphology of the mineral basins in which a peatland develops can influence pool distribution, while more recent work suggested a higher sensitivity of some peatlands to hydrological variations (Bourgault et al., 2017, 2018; Garneau et al., 2017; van Bellen et al., 2018a). Bourgault et al. (2017) have recorded some peatland interactions with the surrounding aquifer, influenced by the local topographic context. Despite the opening of the boreal forest cover from limited regeneration, due in part to shorter fire intervals from the Neoglacial onwards (Asselin and Payette, 2005), no study has yet reported a link between those fires and increased surface runoff that could have influenced higher water levels in peatlands of boreal and subarctic Quebec. Using conceptual modeling supported by DigiBog model simulations, Morris et al. (2015) and van Bellen et al. (2018a) were able to identify the effects of cooling and increased precipitation on peat productivity, decay rates, hydraulic conductivity, and vertical accumulation while highlighting the importance of local topography and groundwater exchanges on peatland hydrology.

In line with conceptual modeling by van Bellen et al. (2018a), this paleoecological and paleohydrological study aimed to document the Holocene and recent ecohydrological trajectories of patterned peatlands in response to climate variations. To do so, two peatlands located in different watersheds north of the Otish Mountains in north-central Quebec were studied. Showing signs of aqualysis, although less pronounced than those in La Grande watershed (150 km northward), these peatlands are also considered as climate-sensitive ecosystems (Garneau et al., 2017; Tahvanainen, 2011) due to their biogeographic location at the boundary between the open and closed boreal forests (van Bellen et al., 2018a), which also corresponds to the ecotone between ombrotrophic and minerotrophic peatland distribution in northeastern Canada.

More specifically, we aimed to (i) document the effect of climate on peatland initiation and long-term development, (ii) evaluate whether the opening of the forest cover influenced by shorter fires intervals during the Neoglacial could have altered the ecohydrological dynamics of the peatlands by increasing surface runoff, and (iii) document the recent changes in peat accumulation rates and vegetation communities related to the 20th century temperature increase.

Study area and sites

The study area is located in north-central Quebec, approximately 150 km southeast of the La Grande-4 reservoir region (Figure 1a). In this region, the Laurentide Ice Sheet retreated between 7800 and 7450 cal. y BP (Dyke et al., 2003). Marine and lacustrine deposits are absent, and the landscape is dominated by low Precambrian outcrops and glacial till interspersed by numerous lakes and rivers. Surficial deposits comprise elongated drumlins, eskers, glaciofluvial and ablation till that do not exceed 40 m in thickness (Lamarche and Hébert, 2020). Gridded ANUSPLIN climate reanalysis data (McKenney et al., 2011) from 1950 to 2017 (grid point: 52.724, −72.213) were used to generate mean annual temperature, mean annual precipitation and growing degree-days (>0°C) (Supplemental Figure S1, available online).

Figure 1.

(a) Location of the studied peatlands in north-central Quebec, eastern Canada, (b) Misask peatland, and (c) Cheinu peatland.

The Misask (52°43′27″N, 72°12′50″W; Figure 1b) and Cheinu peatlands (52°38′48″N, 72°11′31″W; Figure 1c) are located 9 km apart on a north-south axis. These peatlands developed within two different watersheds in shallow topographic depressions and respectively cover total surface areas of 0.102 and 0.148 km². The peatlands have similar ecological characteristics in terms of vegetation and nutrient regime but have distinct surface patterning. Located in the watershed of the Misask River, the Misask peatland is partially patterned with microtopography of alternating low hummocks, lawns, wet hollows and pools covering approximately 10% of its total surface area. The mineral basin topography is quite concave and dominated by gravel and sandy till. Located near the Cheinu lake, the Cheinu peatland complex is characterized by a patterned surface with elongated and parallel pools covering up to 60% of the total surface area. The mineral basin topography in which the Cheinu peatland developed is dominated by boulders that may have originated from an ablation till (Muller, 1983). Only the main patterned section of Cheinu peatland was studied here, as surrounding peat accumulation was considered as recent paludification from lateral peatland expansion. Surface vegetation at both sites is dominated by Sphagnum spp. with a greater abundance of herbaceous taxa (Carex spp. and Trichophorum cespitosum) in hollows and lawns. Hummock vegetation consists mainly of Sphagnum fuscum and S. capillifolium with few low (<1 m) and sparce Picea mariana and Larix laricina trees as well as ericaceous species including Chamaedaphne calyculata and Kalmia angustifolia. Lawns and wet hollows are dominated by Sphagnum fallax, S. angustifolium, and Carex exilis while Menyanthes trifoliata and Nuphar variegatum are found in pools.

Material and methods

Fieldwork and sampling

Prior to the sampling field campaign, peatlands in the studied region were characterized using Google Earth images. Six peatlands were pre-selected and five were surveyed in the field, based on their regional representativeness, size and access to the road (<1 km). The Misask and Cheinu peatlands were selected based on their size, surface morphology and peat depth. Manual probing was carried out systematically at 25 m intervals to reconstruct peat thickness at each site. During the summer of 2016, six cores were retrieved using a Box corer for the surface peat (8 × 8 × 100 cm; Jeglum et al., 1992), and a Russian corer (7.5-cm diameter; Jowsey, 1966) to the base of the peatland. For each peatland, one central core (deepest section: M-C2 and C-C1 cores) and two lateral cores were retrieved from low hummocks (M-L1 and M-L2; C-L1 and C-L2) until the mineral soil was reached. Each core was cut into 50 cm sections, wrapped in plastic film and aluminium foil and transported in rigid tubes (PVC) to be stored in a refrigerator at 4°C until analysis. Vegetation surveys were carried out at each coring site using the Braun-Blanquet (1932) method within 1 m² plots. Testate amoebae surface samples were also sampled from each microform in each peatland following the protocol described by Booth et al. (2010).

Laboratory analyses

Bulk density, organic/mineral content and C:N ratio

In the laboratory, each core was cut into 1-cm slices and stored at 4°C. The dry bulk density, organic matter, and mineral concentrations were calculated using the modified loss-on-ignition (LOI) protocol by Dean (1974). LOI was carried out on contiguous 1 cm³ of fresh peat material, dried overnight at 150°C and burned at 550°C for 3.5 h (Heiri et al., 2001). C:N ratios were measured for the central cores at 4-cm intervals to quantify peat humification (Kuhry and Vitt, 1996) using a Carlo Erba NC 2500 elementary analyzer (Isotopic stable analysis laboratory, Geotop-UQAM).

Plant macrofossil analyses

Plant macrofossil analysis was performed at systematic 4-cm interval from 3-cm³ subsamples to reconstruct vegetation succession since peat initiation. Each sample was immersed in a KOH-5% solution, gently boiled for 15 min and rinsed with distilled water using a 125-μm sieve (Mauquoy et al., 2010). Plant macrofossil analysis was conducted using a stereoscopic microscope (15× to 40×) and a gridded petri dish. For each sample, the relative abundance (%) of peat types (Sphagnum, brown mosses, herbaceous and ligneous) was estimated and individual macrofossil remains (needles, seeds, Ericaceae leaves, Cenoccocum sclerotia and charcoal of local origin (>2 mm; Ohlson and Tryterud, 2000) were counted. Identification of plant macrofossils was conducted using Lévesque et al. (1988), Marie-Victorin (2005) and the botanical reference collection from the Continental Paleoecology Laboratory at Geotop-UQAM (Garneau, 1995). Brown mosses were identified according to Crum and Anderson (1981) and Sphagnum from Laine et al. (2011) on subsample sets of 50 to 100 leaves randomly picked in a Petri dish. Sphagnum identification was performed using a microscope (100× to 400× magnification). When no stem leaves were found, the identification was restricted to the section level and only species with distinct branch leaves, such as Sphagnum papillosum, were identified to the species level. All samples were stored in distilled water with a few drops of 10% diluted hydrochloric acid (HCl) and stored in plastic bags at 4°C.

Testate amoeba analyses and water table depth reconstruction

Following the protocol by Hendon and Charman (1997), samples of 1 cm³ were subsampled at the same 4-cm intervals than the macrofossils, immersed in 100 ml of distilled water and gently boiled for 10 min. One tablet of Lycopodium spores (batch #3862) was added to each sample to calculate test concentration (Stockmarr, 1971). Subsequently, the material was rinsed with distilled water through 355-μm and 15-μm sieves, centrifuged and stored with a drop of glycerine in 2-ml plastic containers at 4°C. Counting was performed with an optical microscope (400×) and specimens were identified using Charman et al. (2000) and Booth (2008). We aimed to count 150 tests per sample (Payne and Mitchell, 2009) and samples with lower test concentrations (<40) expressed with hatched lines in the diagrams have been interpreted with caution (Payne and Mitchell, 2009). Water table depths (WTD) were inferred using with the Lamarre et al. (2013) transfer function with the Rioja package version 0.1-15.1 (Juggins, 2018) in R software (R Core Team, 2017). A correspondence analysis in Canoco 5 (Ter Braak and Smilauer, 2012) was used to confirm the similarity distribution of the samples within the Lamarre et al. (2013) transfer function (Supplemental Figure S2, available online). Water table depths were inferred with the weighted average and tolerance down-weighted (WA-Tol) function, using classical deshrinking and evaluated using a bootstrap cross-validation method with 1000 cycles. Detailed results of these analyses are combined with plant macrofossil data for interpretation. Diagram zones and sub-zones were defined visually from main changes in water table levels and vegetation assemblages.

Dating and chronologies

A total of 43 samples were submitted for AMS radiocarbon dating at the A.E. Lalonde AMS Laboratory of the University of Ottawa (Ontario, Canada). Sphagnum fragments were prioritized (Nilsson et al., 2001) but coniferous needles, seeds (Ericaceae and Carex spp.) and ericaceous leaves were used when Sphagnum abundance was not sufficient. Bulk peat samples were cleaned of roots and rootlets and used when peat was highly decomposed. Radiocarbon dates were calibrated (cal. y BP) using the IntCal13 calibration curve (Reimer et al., 2013) and modern dates were calibrated with the NHZ1 post-bomb atmospheric radiocarbon curve (Hua et al., 2013). All calibrated ages are expressed from the 2σ range and median. Recent chronologies (last 150 years) using lead-210 (²¹⁰Pb) were constructed on both central cores (M-C2 and C-C1). Until reaching the unsupported ²¹⁰Pb limit, 22 levels (0–44 cm) and 28 levels (0–56 cm) were dated for M-C2 and C-C1 respectively (Supplemental Table S1, available online) using an EGG-Ortec Type 576A™ alpha spectrometer and ²⁰⁹Po tracer (Ali et al., 2008; Flynn, 1968; Houel et al., 2006) at the Geotop-UQAM Radiochronology Laboratory. The Constant Rate of Supply (CRS) model was applied to calculate the age of each level (Appleby, 2001). Age-depth models were produced using the R package rbacon v2.4.2 which applies Bayesian statistics using a combination of ²¹⁰Pb and ¹⁴C dating results and prior information to reconstruct peat accumulation (Blaauw and Christen, 2011; R Core Team, 2017). The age of the peat surface was set at −66 cal. y BP, equivalent to the year of coring (i.e. 2016 CE).

Carbon content, C accumulation rates, and peatland C pool

The carbon density (g cm⁻³) was calculated by multiplying the organic matter density determined from LOI measurements by 0.5 (Turunen et al., 2002). Carbon density values were subsequently used to calculate the long-term carbon accumulation rate (LORCA; g m⁻² y⁻¹) by dividing the cumulative C of the entire core by the basal age. Recent apparent rates of C accumulation (RERCA; g m⁻² y⁻¹) for each central core were calculated for the uppermost peat layers using ²¹⁰Pb dating (Ali et al., 2008; Loisel and Garneau, 2010). In order to calculate apparent peat accumulation rates (PAR; cm y⁻¹) and apparent carbon accumulation rates (CAR; g m⁻² y⁻¹), peat thickness and carbon density were divided by the deposition time (y cm⁻¹) of each subsample. The estimated peatland C stock was obtained as in Sheng et al. (2004) based on average depth values, bulk density, LOI and C mass. Peat depth models were realized by Christelle Lambert (UQAM) using a total of 116 and 167 depth values for the Misask and Cheinu peatlands, respectively. Spatial interpolations were generated using the Topo to raster function in the ArcGIS 10.5 software (Figure 3).

Results

Chronologies and PAR

The results of radiocarbon dating and the calibrated ages are presented in Table 1 and the age-depth models in Figure 2.

Table 1.

Detailed AMS radiocarbon dating samples, calibrated ages (2-sigma range and median) and modeled ages (2-sigma range and weighted mean age from the age-depth models (rbacon)).

Core no.	Depth (cm)	Lab number	Dated material	¹⁴C age (a BP)	Calibrated dates		Modeled dates
Core no.	Depth (cm)	Lab number	Dated material	¹⁴C age (a BP)	2σ range (cal. y BP)	Median (cal. y BP)	2σ range (cal. y BP)	wmean (cal. y BP)
M-C2	34	UOC-4600	Sphagnum stems	183 ± 47	31–273	152	31–66	50
	56	UOC-6763	Plant macrofossils	999 ± 26	874–945	910	771–952	860
	68	UOC-6764	Plant macrofossils	1102 ± 26	979–1047	1013	952–1073	1012
	76	UOC-6765	Plant macrofossils	1164 ± 26	1029–1139	1084	1056–1233	1136
	105	UOC-4601	Plant macrofossils	2392 ± 47	2375–2605	2490	2379–2733	2579
	140	UOC-6766	Sphagnum stems	4163 ± 30	4643–4798	4721	4542–4821	4688
	156	UOC-6767	Plant macrofossils	4590 ± 29	5298–5431	5345	5067–5442	5264
	189	UOC-4602	Sorted bulk	5470 ± 47	6225–6306	6260	6033–6401	6254
M-L1	33	UOC-4598	Sorted bulk	Post-bomb^a	0–251	126	1948–1960 CE	1955 CE
	40	UOC-6758	Sorted bulk	171 ± 26	26–268	147	15–282	168
	52	UOC-6759	Plant macrofossils	1191 ± 27	1082–1161	1122	1018–1272	1149
	76	UOC-6760	Sphagnum stems	2085 ± 26	2019–2105	2062	1995–2182	2092
	88	UOC-6761	Sphagnum stems	2469 ± 28	2476–2673	2576	2374–2585	2471
	100	UOC-6762	Plant macrofossils	2450 ± 26	2413–2665	2539	2583–2796	2703
	121	UOC-4595	Plant macrofossils	4098 ± 47	4544–4774	4659	4352–4802	4550
M-L2	41	UOC-4603	Plant macrofossils	394 ± 47	351–496	424	376–615	487
	47	UOC-6768	Plant macrofossils	806 ± 26	700–739	720	680–861	729
	61	UOC-6769	Plant macrofossils	2303 ± 26	2325–2348	2337	2132–2354	2263
	73	UOC-6770	Charred needles	2473 ± 26	2490–2675	2593	2444–2716	2608
	105	UOC-6771	Plant macrofossils	4338 ± 26	4867–4951	4909	3740–4989	4177
	115	UOC-4604	Sorted bulk	3937 ± 47	4305–4454	4380	4162–5207	4440
C-C1	41	UOC-4593	Sphagnum stems	Post-bomb^c	1962–1974 CE	1968 CE	1961–1975 CE	1967 CE
	64	UOC-6773	Sorted bulk	296 ± 26	318–424	371	296–461	372
	80	UOC-6772	Sorted bulk	919 ± 26	805–897	851	753–917	845
	100	UOC-6749	Plant macrofossils	1666 ± 26	1547–1605	1576	1437–1684	1570
	116	UOC-6750	Plant macrofossils	2100 ± 26	2031–2115	2073	1910–2121	2025
	130	UOC-6751	Sorted bulk	2114 ± 26	2051–2128	2090	2064–2301	2193
	150	UOC-4594	Sphagnum stems	2488 ± 47	2474–2682	2578	2501–2782	2661
	172	UOC-6752	Sphagnum stems	5055 ± 32	5761–5878	5820	5648–5890	5775
	200	UOC-4595	Sphagnum stems	5710 ± 76	6428–6610	6519	6328–6744	6520
C-L1	21	UOC-4590	Sorted bulk	Post-bomb^b	1959–1984 CE	1972 CE	1949–1986 CE	1972 CE
	30	UOC-6745	Sorted bulk	251 ± 30	180–397	289	(–5)–415	245
	80	UOC-6747	Plant macrofossils	3799 ± 26	4151–4230	4191	4171–4625	4367
	98	UOC-4591	Plant macrofossils	3980 ± 47	4401–4511	4456	4386–4795	4549
	116	UOC-6748	Sorted bulk	4735 ± 28	5365–5565	5465	4953–5509	5301
	129	UOC-4592	Sorted bulk	4510 ± 47	5077–5268	5173	5173–5845	5490
C-L2	43	UOC-4596	Sphagnum stems	Post-bomb^d	1968–1971 CE	1970 CE	1890–1973 CE	1962 CE
	53	UOC-6753	Sorted bulk	198 ± 26	108–284	196	108–403	254
	68	UOC-6754	Sorted bulk	1154 ± 26	1015–1124	1070	907–1145	1018
	80	UOC-6755	Sorted bulk	1453 ± 26	1323–1369	1346	1302–1474	1352
	104	UOC-6756	Sorted bulk	2288 ± 30	2216–2343	2280	2164–2423	2292
	128	UOC-6757	Plant macrofossils	3358 ± 26	3575–3637	3606	3480–3683	3588
	146	UOC-4597	Sorted bulk	3771 ± 47	4072–4226	4149	3960–4345	4128

F¹⁴C = 1.0090 ± 0.0059.

F¹⁴C = 1.2359 ± 0.0072.

F¹⁴C = 1.4287 ± 0.0083.

F¹⁴C = 1.5306 ± 0.0089.

Figure 2.

Age-depth models for the Misask and Cheinu lateral and central cores, constructed using the rbacon package, version 2.4.2 (Blaauw and Christen, 2011).

Misask peatland – The central core (M-C2; 189 cm) corresponds to the beginning of peat accumulation ca 6250 cal. y BP with a mean peat accumulation rate (PAR) of 0.032 cm y⁻¹ until 4790 cal. y BP (Figure 2). After 4790 cal. y BP, low PAR (mean ranging from 0.019 to 0.017 cm y⁻¹) was recorded until 1840 cal. y BP. Between 1170 and 800 cal. y BP (79–56 cm), a higher PAR of 0.066 cm y⁻¹ was recorded although this trend was subsequently followed by a drastic decrease until 170 cal. y BP (44 cm), with values as low as 0.021 cm y⁻¹. At 30 cal. y BP (1920 CE), the less-compressed and less-decomposed upper peat layer dominated by Sphagnum sect. Acutifolia is characterized by a higher mean PAR of 0.585 cm y⁻¹. There is good agreement between the ²¹⁰Pb and calibrated ¹⁴C date range at 41 cm (1961–1969 CE and 1962–1974 CE, respectively) resulting in a robust combined age-depth model for the central core. The lateral core data (M-L1 and M-L2) show that lateral expansion initiated in Misask peatland at ca 4580 (121 cm) and 4440 cal. y BP (115 cm) from the eastern and western sections, respectively. To account for the age-reversal at the base of M-L2, we applied a mean “prior” accumulation rate to the rbacon model (“acc.mean” = 35 y cm⁻¹), based on the mean accumulation rates for M-C2 and M-L1 (Blaauw and Christen, 2011). Mean accumulation rates are higher in M-L2 than M-L1 with respective values of 0.186 cm y⁻¹ and 0.042 cm y⁻¹. In the upper horizons, a rapid increase in peat accumulation occurred in M-L1 from −20 cal. y BP (mean of 0.630 cm y⁻¹) while the increase in M-L2 cannot be quantified with precision due to lack of accurate dating in the upper horizons. In any case, both increases coincide with vegetation shifts from herbaceous to Sphagnum sect. Acutifolia.

Cheinu peatland – Peat accumulation began ca 6520 cal. y BP (C-C1; 200 cm) while lateral expansion occurred from ca 5490 (C-L1) and 4130 cal. y BP (C-L2) respectively. At the Cheinu peatland, mean PAR for the central core (C-C1) is 0.030 cm y⁻¹ (Figure 2). A very low PAR of ~0.009 cm y⁻¹ between 5890 and 2800 cal. y BP (175–151 cm) was followed by a slight increase to a mean of 0.033 cm y⁻¹. The highest PAR values (mean of 0.703 cm y⁻¹) are recorded in the upper horizons after 40 cal. y BP (1910 CE) to the present. There is good agreement between the ²¹⁰Pb and calibrated ¹⁴C date ranges (at 33 cm: 1909–1915 CE, and 1844–1915 CE, respectively) resulting in a robust combined age-depth model for the central core. To account for the age-reversal at the base of C-L1, we applied a mean “prior” accumulation rate to the rbacon model (“acc.mean” = 30 y cm⁻¹), based on the mean accumulation rates for C-C1 and C-L2 (Blaauw and Christen, 2011). In the lateral sections, PAR is higher in the northwestern section (C-L2) than the southeastern one (C-L1), with respective mean values of 0.269 cm y⁻¹ and 0.144 cm y⁻¹. In both upper horizons, the increase in peat accumulation rates from −50 cal. y BP (C-L1; mean of 0.818 cm y⁻¹) and −10 cal. y BP (C-L2; mean of 0.833 cm y⁻¹) also coincides with the recent shift from herbaceous to Sphagnum sect. Acutifolia as recorded in each of the six cores.

Peatland basin morphometry and carbon accumulation

Misask peatland - This peatland is characterized by a main southeastern basin with a maximal peat depth of 2.2 m located near the central core (M-C2) (Figure 3a). The average long-term apparent rate of carbon accumulation (LORCA) is 17.9 g C m⁻² y⁻¹ while the RERCA calculated from 100 cal. y BP (1850 CE) to the present-day is 98.7 g C m⁻² y⁻¹. When considering the total surface area of the peatland, the carbon pool of Misask peatland is estimated at 10.19 kilotons of C (kt C) for a mean mass per unit area of 99.5 ± 3.2 kg C m⁻².

Figure 3.

Peat depth models for: (a) Misask and (b) Cheinu peatlands (contribution from Christelle Lambert, UQAM).

Cheinu peatland – In the main central section of Cheinu peatland complex, a maximum peat depth of 2.9 m was found in the eastern section (Figure 3b). This maximum peat depth was likely measured between boulders. Peat accumulation spread laterally toward the northwestern sector but with lower depths (mean of 1.60 m) than in the southeastern section (mean of 1.96 m). The LORCA calculated from the central core is 16 g C m⁻² y⁻¹, while the RERCA from 100 cal. y BP to the present-day averages 141.4 g C m⁻² y⁻¹. The carbon pool of Cheinu peatland is estimated at 14.48 kt C, for a mean mass of 98 ± 2.7 kg C m⁻².

Vegetation dynamics and hydrological reconstructions

Misask peatland: Central core M-C2

Since ca 6430 cal. y BP, ecohydrological changes are synthesized into four main periods (Figure 4a; Table 2). Plant assemblages in zone 1 are dominated by herbaceous remains, Sphagnum sect. Cuspidata and brown mosses such as Drepanocladus spp. corresponding to minerotrophic conditions. Despite low test concentration, the dominance of Amphitrema wrightianum in the assemblages suggests a near-surface water table until ca 5250 cal. y BP. The abundance of ligneous remains increased just before Sphagnum sect. Acutifolia became dominant in zone 2 from ca 4790 to 4150 cal. y BP. The tests of Trigonopyxis arcula and Heleopera sphagni suggest a slightly lower water table than in zone 1. Considering the very low number of tests counted in this zone, the interpretation of a lower water table is also supported by the presence of Sphagnum sect. Acutifolia (Bubier et al., 1995). From ca 4150 cal. y BP, the third zone is characterized by a gradual increase in surface wetness with an important decrease in Sphagnum assemblages. In sub-zone 3a, Sphagnum is replaced by a ligneous-herbaceous peat with a high number of Picea mariana and Larix laricina needles and Ericaceae leaves. During this period, generally high N values, and low C:N ratios suggest conditions favorable to peat decomposition (Kuhry and Vitt, 1996), From ca 3660 cal. y BP, a relatively low test concentration inferring high water tables (dominance of A. flavum and A. wrightianum) was followed by a dominance of herbaceous fragments ca 1840 cal. y BP (sub-zone 3b) where lowest C:N ratios were measured. Thereafter, two short dry episodes with low WTD and high CAR were recorded ca 1130 and 970 cal. y BP (76 and 64 cm). Between ca 760 and 110 cal. y BP (54 and 39 cm), very low mean CAR of 14.4 g m⁻² y⁻¹ corresponding to highly decayed peat (high UOM and low C:N ratios) and high mineral content within the peat matrix was registered. From 30 cal. y BP (1920 CE), zone 4 is characterized by an ecosystem shift from herbaceous assemblages to Sphagnum sect. Acutifolia assemblage with lower peat bulk density, high C:N ratios and a change in testate amoeba assemblages from Difflugia pulex to A. flavum and Hyalosphenia elegans. Only a few charcoal fragments (2 fragments > 2 mm) were found around 2070 cal. y BP in the whole peat sequence suggesting that no major fires occurred at the coring location in the past.

Figure 4.

Macrofossil abundance (%) and count (n), dry bulk density, carbon accumulation rates (CAR), testate amoeba assemblages (%) and inferred water table depths for the Misask peatland cores: (a) M-C2, (b) M-L1, and (c) M-L2.

Table 2.

Zonation details of Misask peatland central and lateral cores.

Misask cores	Zones	Depth (cm)	Age (cal. y BP)	Mean PAR (cm y⁻¹)	Trophic status. Dominant plant macrofossils	Dominant testate amoebae
Misask cores	Sub-zones	Depth (cm)	Age (cal. y BP)	Mean PAR (cm y⁻¹)	Trophic status. Dominant plant macrofossils	Dominant testate amoebae
M-C2	Zone 1	189–148 cm	6250–4790	0.032	Rich fen. Herbaceous, Sphagnum sect. Cuspidata and Drepanocladus spp.	A. wrightianum and A. flavum
	Zone 2	148–132 cm	4790–4150	0.019	Open bog. Sphagnum sect. Acutifolia	A. flavum, T. arcula and Heleopera sphagni
	Zone 3	132–32 cm	4150–30
	3a	132–92 cm	4150–1840	0.017	Shrubby fen. Ligneous and herbaceous.	A. flavum and T. arcula
	3b	92–32 cm	1840–30	0.054	Herbaceous fen. Herbaceous and ligneous	A. wrightianum and H. subflava
	Zone 4	32–0 cm	30–present	0.585	Open bog. Sphagnum sect. Acutifolia	A. flavum and H. elegans
M-L1	Zone 1	121–88 cm	4550–2470
	1a	121–100 cm	4550–2700	0.011	Shrubby fen. Herbaceous, ligneous and UOM.	T. arcula, A. flavum and A. wrightianum
	1b	100–88 cm	2700–2470	0.060	Open bog. Sphagnum sect. Acutifolia, herbaceous and ligneous	A. flavum and A. wrightianum
	Zone 2	88–28 cm	2470-(–20)	0.073	Herbaceous fen. Herbaceous and ligneous	A. wrightianum
	Zone 3	28–0 cm	(–20)-present	0.630	Open bog. Sphagnum sect. Acutifolia	Hyalosphenia papilio
M-L2	Zone 1	115–36 cm	4440–420	0.028	Shrubby fen. Herbaceous and ligneous	A. wrightianum, A. flavum and H. sphagni
	Zone 2	36–0 cm	420-present	0.076	Open bog. Sphagnum sect. Acutifolia	H. papilio and A. flavum

Misask peatland: Lateral cores M-L1 and M-L2

In the western (M-L1) and eastern sections (M-L2), lateral peat expansion started around 4500 cal. y BP and recorded relatively synchronous ecohydrological changes (Figure 4b and c; Table 2). At the base of both cores (zone 1), macrofossil assemblages show a dominance of herbaceous and ligneous taxa with sparse Sphagnum remains associated with initial lateral expansion conditions and in which several charcoal fragments were found. In the M-L1 core, the presence of Sphagnum sect. Acutifolia (sub-zone 1b) persisted until 2460 cal. y BP (88 cm) when few charcoal fragments were found (21 fragments > 2 mm) within the horizons just before herbaceous and ligneous taxa became dominant in the macrofossil assemblages. In the M-L2 core, the highest amount of charcoal was found ca 2600 cal. y BP (8 fragments > 2 mm) without any obvious change in the vegetation composition. For both cores, testate amoebae did not provide reliable WTD reconstructions due to low test concentrations although the dominance of A. wrightianum suggests near surface water tables that persisted until −20 cal. y BP in M-L1. The upper zones (zone 2) of both cores also registered a drastic recent ecosystem shift from a dominance of herbaceous and ligneous remnants toward a dominance of Sphagnum sect. Acutifolia and lower water tables (~15 cm) although the shift in M-L2 has not been accurately dated.

Cheinu peatland: Central core C-C1

The Cheinu peatland initiated around 6560 cal. y BP and the central core recorded three main ecohydrological periods (Table 3; Figure 5a). At the base of zone 1 (sub-zone 1a), the presence of Sphagnum (sect. Acutifolia and sect. Subsecunda), Picea/Larix needles and Ericaceae suggests initial ombrotrophic conditions. This was followed in sub-zone 1b (ca 5920 cal. y BP), by increased ligneous and herbaceous remnants in which few charcoal fragments were found (3 fragments > 2 mm) and a strong decrease in PAR of ~0.008 cm y⁻¹ was registered. This period was followed by a short return to conditions favorable for Sphagnum sect. Cuspidata and herbaceous species (sub-zone 1c). From ca 2520 cal. y BP, Sphagnum spp. disappeared while herbaceous and ligneous remnants dominated the vegetation assemblages (zone 2). Ligneous remnants with high testate amoeba concentration inferring a mean WTD of 3.5 cm (sub-zone 2a) were followed by herbaceous assemblages (sub-zone 2b) from 1810 to 40 cal. y BP where high bulk density and a low C:N ratio indicate very high decay rates. Testate amoeba assemblages dominated by A. wrightianum suggest a relatively high surface wetness that gradually shifted toward drier conditions at the surface. As in the Misask peatland, the most recent zone (zone 3) is dominated by Sphagnum sect. Acutifolia with higher PAR than in zone 2. Inferred WTD show stable and apparent drier conditions from 40 cal. y BP (1910 CE) to the present-day.

Table 3.

Zonation details of Cheinu peatland central and lateral cores.

Cheinu Cores	Zones	Depth (cm)	Age (cal. y BP)	Mean PAR (cm y⁻¹)	Trophic status. Dominant plant macrofossils	Dominant testate amoeba
Cheinu Cores	Sub-zones	Depth (cm)	Age (cal. y BP)	Mean PAR (cm y⁻¹)	Trophic status. Dominant plant macrofossils	Dominant testate amoeba
C-C1	Zone 1	200–144 cm	6520–2520
	1a	200–176 cm	6520–5920	0.041	Woody bog. Sphagnum spp. and ligneous (Picea needles)	H. rosea and Difflugia rubescens
	1b	176–152 cm	5920–2880	0.009	Woody fen. Ligneous and herbaceous	T. arcula and H. sphagni
	1c	152–144 cm	2880–2520	0.033	Herbaceous Fen. Sphagnum sect. Cuspidata and herbaceous	A. flavum and Heleopera rosea
	Zone 2	144–48 cm	2520–40
	2a	144–108 cm	2520–1810	0.055	Shrubby fen. Ligneous and herbaceous.	A. wrightianum, A. flavum and H. rosea
	2b	108–48 cm	1810–40	0.040	Herbaceous fen. Herbaceous and ligneous	A. wrightianum and H. rosea
	Zone 3	48–0 cm	40-present	0.703	Open bog. Sphagnum sect. Acutifolia	H. elegans
C-L1	Zone 1	129–76	5490–3960
	1a	129–112 cm	5490–5190	0.058	Rich fen. UOM, Herbaceous and Sphagnum sect. Cuspidata.	D. rubescens and T. arcula.
	1b	112–76 cm	5190–3880	0.034	Rich fen. Drepanocladus spp., ligneous and Sphagnum spp.	A. wrightianum
	Zone 2	76–12 cm	3960-(–50)	0.113	Herbaceous fen. Herbaceous and ligneous	A. wrightianum
	Zone 3	12–0 cm	(–50)-present	0.818	Open bog. Sphagnum sect. Acutifolia	A. flavum, H. elegans and H. papilio
C-L2	Zone 1	146–132 cm	4130–3750	0.035	Woody bog. Ligneous and Sphagnum spp.	H. sphagni and T. arcula
	Zone 2	132–44 cm	3750-(–10)	0.031	Herbaceous fen. Herbaceous and ligneous	A. wrightianum
	Zone 3	44–0	(–10)-present	0.833	Open bog. Sphagnum sect. Acutifolia	Nebela militaris, H. papilio and H. elegans

Figure 5.

Macrofossil abundance (%) and count (n), dry density, carbon accumulation rates (CAR), testate amoeba assemblages (%) and inferred water table depths for Cheinu peatland cores: (a) C-C1, (b) C-L1, and (c) C-L2.

Cheinu lateral cores C-L1 and C-L2

Lateral peat expansion in the southern (C-L1) and northwestern sections (C-L2) of the Cheinu peatland started around 5500 and 4130 cal. y BP, respectively (Table 3; Figure 5b and c). In zone 1, the C-L1 core initiated under minerotrophic conditions characterized by the presence of herbaceous species and high percentages of UOM, while the C-L2 core initiated under more oligotrophic conditions as Sphagnum, ligneous and herbaceous peat dominated. The C-L2 core did not record important ecohydrological variations following Sphagnum initiation compared to C-L1. In the C-L1 core, vegetation assemblages such as brown mosses, Larix laricina and Myrica gale suggest rich minerotrophic conditions with near-surface water tables which is consistent with the presence of A. wrightianum. For both lateral cores, zone 2 is marked by a high abundance of herbaceous fragments, a high peat bulk density and a very low testate amoeba concentration that suggest a highly decomposed peat. No charcoal was found in C-L1 and only few fragments (n: 3 > 2 mm) were counted at ca 3870 cal. y BP in C-L2. The upper parts of both lateral cores (zone 3) also show a dominance of Sphagnum sect. Acutifolia which confirms the recent ecosystem shift.

Discussion

Peatland initiation

In north-central Quebec, the retreat of the Laurentide Ice Sheet occurred between 7800 and 7450 cal. y BP (Dyke et al., 2003), which suggests a delay of more than 1000 years before peat initiated as observed in the La Grande river watershed (Beaulieu-Audy et al., 2009). Peat accumulation occurred relatively synchronously in the two studied peatland ecosystems even if their mineral substrate, basin topography and watershed configuration differed slightly. The warmer and drier Holocene Thermal Maximum (HTM) period, which occurred before 5000 cal. y BP in northern Quebec (Oris et al., 2014; Viau and Gajewski, 2009), likely favored a decrease in wetness in topographic depressions, facilitating paludification and Sphagnum invasion as also recorded in other regions (Beaulieu-Audy et al., 2009; Garneau et al., 2017; van Bellen et al., 2013). The Cheinu peatland initiated as ombrotrophic (6560–5920 cal. y BP) in its deepest section. The amount of charcoal fragments found at its base coincides with high fire occurrence in the surrounding regional forests (Asselin et al., 2016; El-Guellab et al., 2015) and confirm the warm and dry conditions at that period. Likely influenced by the local basin topography, peat initiated at the Misask site under minerotrophic conditions but shifted rapidly to ombrotrophy due to the warmer summer conditions (Fréchette et al., 2018) that influenced the growing season length and promoted rapid peat accumulation.

Peatland lateral expansion

A global shift in atmospheric circulation followed the warm and dry climate conditions of the HTM (Fréchette et al., 2018; Payette, 1984; Payette and Filion, 1993) and an increase in moisture conditions favored peat lateral expansion in the studied peatlands from ca 5000 cal. y BP, which was also reported in other studies from the Northern Hemisphere (Korhola et al., 2010; Ruppel et al., 2013; Yu et al., 2009). Wetter climate conditions seem to have primarily controlled lateral expansion (Bauer et al., 2003; Loisel et al., 2013) by initiating synchronous paludification in 3 of 4 lateral cores between 4508 and 4130 cal. y BP.

From the Neoglacial cooling to the end of the Little Ice Age

Following the HTM, no evidence of major fire was registered within the peat sequences. A change in the vegetation assemblages through a dominance of ligneous and herbaceous species from ca 3500 to 3000 y BP within the two peatlands is associated to cooler and wetter climate conditions as synthesized in Figure 6. Shorter growing seasons combined with higher precipitation and increased recharge from the catchments during the Neoglacial cooling (Viau and Gajewski, 2009) likely transformed the two studied peatlands into herbaceous-ligneous oligotrophic fens that shifted to herbaceous-dominated ecosystems at respectively ca 1840 and 1830 cal. y BP. As WTD reconstructions showed an increase in surface wetness for both central cores from around 3400 and 2880 cal. y BP in cores M-C2 (Misask) and C-C1 (Cheinu) respectively, data suggest that it took about 1500 to 1000 years of relatively high water tables to exceed ecosystem resilience (Belyea, 2009) and transform the ecological state of the peatlands to persisting wet-herbaceous environments.

Figure 6.

Synthesis of the reconstructed water table depth and CAR for the Misask (M-C2) and Cheinu (C-C1) central cores and the northern Quebec climate reconstruction (mean July temperature and mean annual precipitations anomalies) from Viau and Gajewski (2009).

In line with Garneau et al. (2017), we suggest that wetter and colder conditions reduced evapotranspiration and limited growing season length and peat productivity. Increased wetness, also influenced by the size of the watershed (White and Payette, 2016) and groundwater inflow from the adjacent mineral substrate (van Bellen et al., 2018a), may have initiated relatively synchronous changes in peatland ecohydrological dynamics over the last 2000 years also registered in peatlands 150 km northward (van Bellen et al., 2013). No evidence of increased runoff caused by fires and the subsequent opening of the forest cover (Asselin and Payette, 2005) adjacent to the peatlands was confirmed here. The conceptual model developed by van Bellen et al. (2018a) and supported by simulations of the DigiBog model confirmed that cooling, increased precipitation and increased recharge from the catchment were required for wetter peatland surface conditions to persist.

The effects of the Neoglacial cooling registered by different proxies in eastern Canada (Payette et al., 1989; Payette and Filion, 1993) peaked after 2000 cal BP with permafrost aggradation in subarctic Quebec (Bhiry et al., 2007; Bhiry and Robert, 2006; Lamarre et al., 2012). During this period, the Cheinu and Misask peatlands registered low CAR and herbaceous-dominated environments with high water tables that persisted in both peatlands until the end of the Little Ice Age, as documented by Arlen-Pouliot and Payette (2015), Loisel et al. (2013) and van Bellen et al. (2013). Only the central core of the Misask peatland (between 1340 and 730 cal. y BP) may have registered the warmer “Medieval Climate Anomaly” (MCA) conditions, which coincided with increased C accumulation in many northern peatlands from ca 1000 to 800 cal. y BP (Charman et al., 2013).

During the Little Ice Age, permafrost aggradation was documented in ombrotrophic peatlands of the boreal and subarctic regions of northwestern Québec (Thibault and Payette, 2009; Tremblay et al., 2014). During this cold climatic episode, northern peatlands in eastern Canada registered important lowering in CAR (Garneau et al., 2014; Magnan and Garneau, 2014; Primeau and Garneau, 2021; van Bellen et al., 2013) as also observed in the current study sites without evidence of relic permafrost nowadays. We can hypothesize that persistence of ice lenses within the horizons with very short growing seasons may have limited peat accumulation for several decades.

Recent ecohydrological changes

Over the last century, shifts toward drier conditions associated with a sudden ecosystem change from herbaceous oligotrophic to Sphagnum ombrotrophic conditions occurred within the six analyzed cores (Figure 6; Supplemental Figure S3, available online). Although the recent Sphagnum expansion was not supported by detailed ²¹⁰Pb chronologies in the lateral cores, the data suggest a widespread ecosystem state shift in both peatlands corresponding to the beginning of the 20th century. Similar recent Sphagnum expansion was also documented in other northern peatlands (Loisel and Yu, 2013; Primeau and Garneau, 2021; van Bellen et al., 2013, 2018b). When considering the current climate warming trend, this ecosystem change coincided with the registered increase in temperature and growing degree-days (>0°C) from 1950 to 2017 (Supplemental Figure S1, available online). This suggests that longer and warmer growing seasons may have enhanced peat primary production (Loisel et al., 2012; Loisel and Yu, 2013; van Bellen et al., 2018b) and influenced patterned fens to shift recently from oligotrophic to ombrotrophic conditions as also recorded in other sites located at the same ecoclimatic zonation (Primeau and Garneau, 2021; van Bellen et al., 2013). While the recent impacts of 20th century warming have been previously identified from permafrost degradation in eastern Canada (Payette et al., 2004; Tremblay et al., 2014; Vallée and Payette, 2007) and shrub growth increase (Duguay et al., 2015), our study is the first to document peatland ecosystem state shift and increased peat accumulation in this region. Rapid and recent accumulation at the sites is also expressed as important paludification of the adjacent forest border and pool infilling as shown in Supplemental Figure S4, available online.

Carbon accumulation

LORCA values calculated for the central core of Misask and Cheinu peatlands (17.9 and 16 g C m⁻² y⁻¹) are slightly lower than the average of ±23 g C m⁻² y⁻¹ estimated for northern peatlands (Garneau et al., 2014; Loisel et al., 2014), but within the range of 10.3 and 22.6 g C m⁻² y⁻¹ estimated in surrounding regions (Loisel and Garneau, 2010; van Bellen et al., 2011, 2012). In each core, Holocene variations in C accumulation rates do show relatively synchronous changes, but CARs globally stayed between 10 and 25 g C m⁻² y⁻¹. The recorded variations mainly suggest the influence of changes in plant communities and hydrological variations (Magnan and Garneau, 2014; Yu et al., 2009). The charcoal data do not suggest the occurrence of fires at the coring locations but may indicate fires from the surrounding forest borders without apparent consequences on peatland dynamics. However, data show significant increases in apparent CARs that started between 30 and 40 cal. y BP (1920–1910 CE) in the two central cores. Even when considering the incomplete decay in the acrotelm, the recent C accumulation changes coincide with an ecosystem state shift with a drastic increase in Sphagnum sect. Acutifolia most probably stimulated by the recent warming trend (Supplemental Figure S1, available online; Loisel and Yu, 2013).

Conclusion

This study represents the first multiproxy reconstruction of peatlands located in north-central Quebec at the biogeographic limit between the open and closed boreal forests. Results show that peatlands in the region initiated ca 6500 cal. y BP under spatially variable ombrotrophic and minerotrophic conditions. Paleohydrological records show a general increase in surface wetness during the Neoglacial cooling period with shifts in vegetation communities and nutrient status that persisted until the last century. As the results do not support the hypothesis of an increase in surface runoff influenced by the opening of forest cover after fire events, we suggest that the rise in wetness has likely been influenced by lower peat productivity, reduced evapotranspiration and groundwater inflow from the adjacent mineral substrate. The aqualysis phenomenon may have started during the Neoglacial cooling and persisted until the end of the Little Ice Age in the region. Following the LIA, the relatively synchronous ecosystem state shift from herbaceous oligotrophic fens to Sphagnum sect. Acutifolia bogs suggests a recent response of high-latitude peatlands to the ongoing climate warming that influences Sphagnum growth, carbon accumulation rates and a possible northward migration of the biogeographic limit of ombrotrophic ecosystems. These results illustrate the sensitivity of peatlands to a combination of internal and external forcings such as climate that are still not well represented into numerical models and need further attention in the future.

Supplemental Material

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Supplemental material, sj-png-5-hol-10.1177_0959683620988051 for Long-term and recent ecohydrological dynamics of patterned peatlands in north-central Quebec (Canada) by Mylène Robitaille, Michelle Garneau, Simon van Bellen and Nicole K Sanderson in The Holocene

Footnotes

Acknowledgements

We would like to thank Benjamin Jacob and Caroline Courchesne from the Renard mine and Marie Larocque, Sylvain Gagné, and Louis-Martin Pilote for their help in the field. We are also grateful to Dr Bassam Ghaleb and Dr Jean-François Hélie from the GEOTOP Radiochronology and Stable isotope geochemistry laboratories for lead-210 and C:N ratio analyses and to the A.E. Lalonde AMS Laboratory (University of Ottawa) training program for radiocarbon chronologies. Special thanks to Christelle Lambert (UQAM) who provided the 3D depth models, Carole-Anne Kenny for the mapping contribution and Les Tourbeux for their inspiration and continuous support. Thanks also to Dr. Gabriel Magnan, Professors Serge Payette (Laval University) and Etienne Boucher (UQAM) and two anonymous reviewers for their constructive comments on earlier versions of the manuscript. Thank you also to Dan McKenney (Canadian Forest Service, NRCan) for the update of the climate data, Guillaume Dueymes (Centre ESCER, UQAM) for the climate data preparation and accessibility, to Dr André Viau (University of Ottawa) who kindly provided data on climate reconstructions.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Funding was provided by the Mitacs Acceleration program in collaboration with Stornoway Diamond Corporation, NSERC-CRD (RDCPJ 51342-17) to MG in collaboration with Stornoway Diamond Corporation and Nemaska Lithium and the NSTP (Northern Scientific Training Program) to MR.

ORCID iD

Mylène Robitaille

Supplemental material

Supplemental material for this article is available online.

References

Ali

Ghaleb

Garneau

, et al. (2008) Recent peat accumulation rates in minerotrophic peatlands of the Bay James region, Eastern Canada, inferred by 210Pb and 137Cs radiometric techniques. Applied Radiation and Isotopes 66(10): 1350–1358.

Appleby

(2001) Chronostratigraphic techniques in recent sediments. In: Last

Smol

(ed.), Tracking Environmental Change Using Lake Sediments. Dordrecht: Kluwer Academic Publishers, pp.171–203.

Arlen-Pouliot

Payette

(2015) The influence of climate on pool inception in boreal fens. Botany 93(10): 637–649.

Asselin

Payette

(2005) Late-Holocene opening of the forest tundra landscape in northern Québec, Canada. Global Ecology and Biogeography 14: 307–313.

Asselin

Grondin

Lavoie

, et al. (2016) Fires of the last millennium led to landscapes dominated by early successional species in Québec’s clay belt boreal forest, Canada. Forests 7(9): 205.

Bauer

Gignac

Vitt

(2003) Development of a peatland complex in boreal western Canada: lateral site expansion and local variability in vegetation succession and long-term peat accumulation. Canadian Journal of Botany 81(8): 833–847.

Beaulieu-Audy

Garneau

Richard

PJH

, et al. (2009) Holocene palaeoecological reconstruction of three boreal peatlands in the La Grande Rivière region, Québec, Canada. The Holocene 19(3): 459–476.

Belyea

(2007) Climatic and topographic limits to the abundance of bog pools. Hydrological Processes 21(5): 675–687.

Belyea

(2009) Nonlinear dynamics of peatlands and potential feedbacks on the climate system. Carbon Cycling in Northern Peatlands 184: 5–18.

10.

Bhiry

Robert

ÉC

(2006) Reconstruction of changes in vegetation and trophic conditions of a palsa in a permafrost peatland, subarctic Québec, Canada. Écoscience 13: 56–65.

11.

Bhiry

Payette

Robert

ÉC

(2007) Peatland development at the arctic tree line (Québec, Canada) influenced by flooding and permafrost. Quaternary Research 67(3): 426–437.

12.

Blaauw

Christen

(2011) Bacon, version 2.4.2. Belfast: Queen’s University.

13.

Booth

(2008) Testate amoebae as proxies for mean annual water-table depth in Sphagnum-dominated peatlands of North America. Journal of Quaternary Science 23(1): 43–57.

14.

Booth

Lamentowicz

Charman

(2010) Preparation and analysis of testate amoebae in peatland palaeoenvironmental studies. Mires and Peat 7(2): 1–7.

15.

Bourgault

Larocque

Garneau

(2017) Quantification of peatland water storage capacity using the water table fluctuation method. Hydrological Processes 31(5): 1184–1195.

16.

Bourgault

Larocque

Garneau

, et al. (2018) Quantifying peat hydrodynamic properties and their influence on water table depths in peatlands of southern Quebec (Canada). Ecohydrology 11(7): e1976.

17.

Braun-Blanquet

Conrad

Fuller

(1932) Plant Sociology. New York: McGraw-Hill Book Co. Inc.

18.

Bubier

Moore

Juggins

(1995) Predicting methane emission from bryophyte distribution in northern Canadian peatlands. Ecology 76(3): 677–693.

19.

Charman

Beilman

Blaauw

, et al. (2013) Climate-related changes in peatland carbon accumulation during the last millennium. Biogeosciences 10(2): 929–944.

20.

Charman

Hendon

Woodland

(2000) The identification of testate amoebae (Protozoa: Rhizopoda) in peats. Technical Guide No. 9. Quaternary Research Association, London, p.147.

21.

Cliche-Trudeau

Garneau

Pelletier

(2013) Methane fluxes from a patterned fen of the northeastern part of the La Grande river watershed, James Bay, Canada. Biogeochemistry 113: 409–422.

22.

Cliche-Trudeau

Garneau

Pelletier

(2014) Interannual variability in the CO₂ balance of a boreal patterned fen, James Bay, Canada. Biogeochemistry 118: 371–387.

23.

Comas

Slater

Reeve

(2011) Pool patterning in a northern peatland: Geophysical evidence for the role of postglacial landforms. Journal of Hydrology 399(3–4): 173–184.

24.

Crum

Anderson

(1981) Mosses of Eastern North America, vols. 1–2. New York: Columbia University Press, pp.1328.

25.

Dean

(1974) Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition; comparison with other methods. Journal of Sedimentary Research 44(1): 242–248.

26.

Dissanska

Bernier

Payette

(2009) Object-based classification of very high resolution panchromatic images for evaluating recent change in the structure of patterned peatlands. Canadian Journal of Remote Sensing 35(2): 189–215.

27.

Duguay

Bernier

Lévesque

, et al. (2015) Potential of C and X Band SAR for shrub growth monitoring in sub-Arctic environments. Remote Sensing 7(7): 9410–9430.

28.

Dyke

Moore

Robertson

(2003) Deglaciation of North America. Ottawa, Ontario, Canada: Geological Survey of Canada.

29.

El-Guellab

Asselin

Gauthier

, et al. (2015) Holocene variations of wildfire occurrence as a guide for sustainable management of the northeastern Canadian boreal forest. Forest Ecosystems 2(1): 1–7.

30.

Flynn

(1968) The determination of low levels of polonium-210 in environmental materials. Analytica Chimica Acta 43(2): 221–227.

31.

Foster

Fritz

(1987) Mire development, pool formation and landscape processes on patterned fens in Dalarna, Central Sweden. Journal of Ecology 75(2): 409–437.

32.

Foster

King

(1984) Landscape features, vegetation and developmental history of a patterned fen in south-eastern Labrador, Canada. Journal of Ecology 72(1): 115–143.

33.

Foster

King

Glaser

, et al. (1983) Origin of string patterns in boreal peatlands. Nature 306: 256–258.

34.

Fréchette

Richard

PJH

Grondin

, et al. (2018) Histoire postglaciaire de la végétation et du climat des pessières et des sapinières de l’ouest du Québec. Mémoire de recherche forestière 179. Ministère des Forêts, de la Faune et des Parcs, Québec.

35.

Garneau

(1995) Collection de référence de graines et autres macrofossiles végétaux de taxons provenant du Québec méridional et boréal et de l’arctique canadien. Sainte-Foy: Geological Survey of Canada, Division de la science des terrains, pp.47.

36.

Garneau

Tremblay

Magnan

(2017) Holocene pool formation in oligotrophic fens from boreal Québec in northeastern Canada. The Holocene 28(3): 396–407.

37.

Garneau

van Bellen

(2016) Synthèse de la valeur et la répartition du stock de carbone terrestre au Quebec, Rapport final. Ministère du Développement durable, de l’Environnement et de Lutte contre les changements climatiques du Québec, Québec.

38.

Garneau

van Bellen

Magnan

, et al. (2014) Holocene carbon dynamics of boreal and subarctic peatlands from Québec, Canada. The Holocene 24(9): 1043–1053.

39.

Gorham

Lehman

Dyke

, et al. (2007) Temporal and spatial aspects of peatland initiation following deglaciation in North America. Quaternary Science Reviews 26(3–4): 300–311.

40.

Heiri

Lotter

Lemcke

(2001) Loss on ignition as a method for estimating organic and carbonate content in sediments: Reproducibility and comparability of results. Journal of Paleolimnology 25(1): 101–110.

41.

Hendon

Charman

(1997) The preparation of testate amoebae (Protozoa: Rhizopoda) samples from peat. The Holocene 7(2): 199–205.

42.

Houel

Louchouarn

Lucotte

, et al. (2006) Translocation of soil organic matter following reservoir impoundment in boreal systems: Implications for in situ productivity. Limnology and Oceanography 51(3): 1497–1513.

43.

Hua

Barbetti

Rakowski

(2013) Atmospheric radiocarbon for the period 1950–2010. Radiocarbon 55(4): 2059–2072.

44.

Jeglum

Rothwell

Berry

(1992) A peat sampler for rapid survey (Technical note). Canadian Forestry Service 13: 921–932.

45.

Jowsey

(1966) An improved peat sampler. New Phytologist 65: 245–248.

46.

Juggins

(2018) Rioja, version 0.1-15.1. Newcastle upon Tyne: University of Newcastle.

47.

Korhola

Ruppel

Seppä

, et al. (2010) The importance of northern peatland expansion to the late-Holocene rise of atmospheric methane. Quaternary Science Reviews 29(5): 611–617.

48.

Kuhry

Vitt

(1996) Fossil Carbon/Nitrogen ratios as a measure of peat decomposition. Ecology 77(1): 271–275.

49.

Laine

Harju

Timonen

, et al. (2011) The intricate beauty of Sphagnum mosses: A Finnish guide to identification. Department of Forest Ecology, University of Helsinki.

50.

Lamarche

Hébert

(2020) Géologie des dépôts de surface de la région de la rivière Eastmain supérieure (SNRC 23D05, 23D06, 23D11, 23D12, 33A08 à 33A10). Ministère de l’Énergie et des Ressources naturelles, Québec; RP 2019-02.

51.

Lamarre

Garneau

Asnong

(2012) Holocene paleohydrological reconstruction and carbon accumulation of a permafrost peatland using testate amoeba and macrofossil analyses, Kuujjuarapik, subarctic Québec, Canada. Review of Palaeobotany and Palynology 186: 131–141.

52.

Lamarre

Magnan

Garneau

, et al. (2013) A testate amoeba-based transfer function for paleohydrological reconstruction from boreal and subarctic peatlands in northeastern Canada. Quaternary International 306: 88–96.

53.

Lévesque

PEM

Dinel

Larouche

(1988) Guide illustré des macrofossiles végétaux des tourbières du Canada. Agriculture Canada. Ministère des approvisionnements et services, Publication no. 1817.

54.

Loisel

Gallego-Sala

(2012) Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length. Biogeosciences 9: 2737–2746.

55.

Loisel

Garneau

(2010) Late-Holocene paleoecohydrology and carbon accumulation estimates from two boreal peat bogs in eastern Canada: Potential and limits of multi-proxy archives. Palaeogeography, Palaeoclimatology, Palaeoecology 291: 493–533.

56.

Loisel

(2013) Recent acceleration of carbon accumulation in a boreal peatland, south central Alaska. Journal of Geophysical Research: Biogeosciences 118(1): 41–53.

57.

Loisel

Beilman

, et al. (2014) A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation. The Holocene 24(9): 1028–1042.

58.

Loisel

Parsekian

, et al. (2013) Quantifying landscape morphology influence on peatland lateral expansion using ground-penetrating radar (GPR) and peat core analysis. Journal of Geophysical Research: Biogeosciences 118(2): 373–384.

59.

Magnan

Garneau

(2014) Climatic and autogenic control on Holocene carbon sequestration in ombrotrophic peatlands of maritime Quebec, eastern Canada. The Holocene 24(9): 1054–1062.

60.

Marie-Victorin

(2005) Flore Laurentienne. Montréal: Les Presses de l’Université de Montréal.

61.

Mauquoy

Hughes

PDM

van Geel

(2010) A protocol for plant macrofossil analysis of peat deposits. Mires and Peat 7(06): 1–5.

62.

McKenney

Hutchinson

Papadopol

, et al. (2011) Customized spatial climate models for North America. Bulletin of the American Meteorological Society 92(12): 1612–1622.

63.

Morris

Baird

Young

, et al. (2015) Untangling climate signals from autogenic changes in long-term peatland development. Geophysical Research Letters 42(10): 10788–10797.

64.

Muller

(1983) Till genesis and the glacier sole. In: Evenson

Schlüchter

Rabassa

(eds) Tilts and Related Deposits: Genesis, Petrology, Application, Stratigraphy. Rotterdam: A. A. Balkema, pp.19–22.

65.

Nilsson

Klarqvist

Bohlin

, et al. (2001) Variation in 14C age of macrofossils and different fractions of minute peat samples dated by AMS. The Holocene 11(5): 579–586.

66.

Ohlson

Tryterud

(2000) Interpretation of the charcoal record in forest soils: Forest fires and their production and deposition of macroscopic charcoal. The Holocene 10(4): 519–525.

67.

Oris

Asselin

Finsinger

, et al. (2014) Long-term fire history in northern Quebec: implications for the northern limit of commercial forests. Journal of Applied Ecology 51(3): 675–683.

68.

Payette

(1984) Peat inception and climatic change in northern Quebec. In: Mörner

Karlén

(eds) Climatic Change on a Yearly to Millenial Basis. Dordrecht: Reidel, pp.173–179.

69.

Payette

Delwaide

Caccianiga

, et al. (2004) Accelerated thawing of subarctic peatland permafrost over the last 50 years. Geophysical Research Letters 31(18).

70.

Payette

Filion

(1993) Holocene water-level fluctuations of a subarctic lake at the tree line in northern Québec. Boreas 22(1): 7–14.

71.

Payette

Filion

Delwaide

, et al. (1989) Reconstruction of tree-line vegetation response to long-term climate change. Nature 341: 429–432.

72.

Payette

Rochefort

(2001) Écologie des tourbières du Québec-Labrador. Québec: Les Presses de l’Université Laval.

73.

Payne

Mitchell

EAD

(2009) How many is enough? Determining optimal count totals for ecological and palaeoecological studies of testate amoebae. Journal of Paleolimnology 42(4): 483–495.

74.

Primeau

Garneau

(2021) Carbon accumulation in peatlands along a boreal to subarctic transect in eastern Canada. The Holocene. Epub ahead of print 17 January 2021. DOI: 10.1177/0959683620988031.

75.

R Core Team (2017) R: A language and environment for statistical computing. R Foundation for Statistical Computing. Available at: http://www.R-project.org/ (accessed 1 December 2017).

76.

Reimer

Bard

Bayliss

, et al. (2013) IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal bp. Radiocarbon 55(4): 1869–1887.

77.

Ruppel

Väliranta

Virtanen

, et al. (2013) Postglacial spatiotemporal peatland initiation and lateral expansion dynamics in North America and northern Europe. The Holocene 23(11): 1596–1606.

78.

Rydin

Jeglum

(2013) The Biology of Peatlands. Oxford: Oxford University Press.

79.

Seppälä

Koutaniemi

(1985) Formation of a string and pool topography as expressed by morphology, stratigraphy and current processes on a mire in Kuusamo, Finland. Boreas 14(4): 287–309.

80.

Sheng

Smith

Macdonald

, et al. (2004) A high-resolution GIS-based inventory of the west Siberian peat carbon pool. Global Biogeochemical Cycles 18(3).

81.

Stockmarr

(1971) Tablets with spores used in absolute pollen analysis. Pollen et Spores XIII (January 1971): 615–621.

82.

Tahvanainen

(2011) Abrupt ombrotrophication of a boreal aapa mire triggered by hydrological disturbance in the catchment. Journal of Ecology 99(2): 404-415.

83.

Tardif

St-Hilaire

Roy

, et al. (2009) Statistical properties of hydrographs in minerotrophic fens and small lakes in mid-latitude Québec, Canada. Canadian Water Resources Journal / Revue canadienne des ressources hydriques 34(4): 365–380.

84.

Tarnocai

Kettles

Lacelle

(2005) Peatlands of Canada database. Agriculture and Agri-Food Canada, Ottawa.

85.

Tarnocai

Kettles

Lacelle

(2011) Peatlands of Canada. Open File 6561. Geological Survey of Canada, Ottawa.

86.

Ter Braak

CJF

Smilauer

(2012) Canoco 5, Windows release (5.00). Software for multivariate data exploration, testing, and summarization. Biometris, Plant Research International, Wageningen.

87.

Thibault

Payette

(2009) Recent permafrost degradation in bogs of the James Bay area, northern Quebec, Canada. Permafrost and Periglacial Processes 20(4): 383–389.

88.

Tremblay

Bhiry

Lavoie

(2014) Long-term dynamics of a palsa in the sporadic permafrost zone of northwestern Quebec (Canada). Canadian Journal of Earth Sciences 51(5): 500–509.

89.

Turunen

Tomppo

Tolonen

, et al. (2002) Estimating carbon accumulation rates of undrained mires in Finland–application to boreal and subarctic regions. The Holocene 12(1): 69–80.

90.

Vallée

Payette

(2007) Collapse of permafrost mounds along a subarctic river over the last 100 years (northern Québec). Geomorphology 90(1): 162–170.

91.

van Bellen

Dallaire

Garneau

, et al. (2011) Quantifying spatial and temporal Holocene carbon accumulation in ombrotrophic peatlands of the Eastmain region, Quebec, Canada. Global Biogeochemical Cycles 25(2).

92.

van Bellen

Garneau

Ali

, et al. (2012) Did fires drive Holocene carbon sequestration in boreal ombrotrophic peatlands of eastern Canada? Quaternary Research 78(1): 50–59.

93.

van Bellen

Garneau

Ali

, et al. (2013) Poor fen succession over ombrotrophic peat related to late-Holocene increased surface wetness in subarctic Quebec, Canada. Journal of Quaternary Science 28(8): 748–760.

94.

van Bellen

Garneau

Baird

, et al. (2018a) Exploring pathways to late-Holocene increased surface wetness in subarctic peatlands of eastern Canada. Quaternary Research 90(1): 83–95.

95.

van Bellen

Magnan

Davies

, et al. (2018b) Testate amoeba records indicate regional 20th-century lowering of water tables in ombrotrophic peatlands in central-northern Alberta, Canada. Global Change Biology 24(7): 2758–2774.

96.

Viau

Gajewski

(2009) Reconstructing millennial-scale, regional paleoclimates of boreal Canada during the Holocene. Journal of Climate 22(2): 316–330.

97.

White

Payette

(2016) Pool size structure indicates developmental stages of boreal fens. Botany 94(8): 643–651.

98.

(2012) Northern peatland carbon stocks and dynamics: a review. Biogeosciences 9(10): 4071-–4085.

99.

Beilman

Jones

(2009) Sensitivity of northern peatland carbon dynamics to Holocene climate change. In: Baird

Belyea

Comas

, et al. (eds) Carbon Cycling in Northern Peatlands. Geophysical Monograph Series, vol. 184. Washington, DC: American Geophysical Union, pp. 55–69.

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