Carbon accumulation in peatlands along a boreal to subarctic transect in eastern Canada

Abstract

In this study, we investigated the links between peat carbon accumulation and past ecological and hydrological conditions in three peatlands (Bouleau, Mista, Auassat) which developed along a South-North transect within a watershed encompassing the boreal and subarctic domain in Eastern Canada. Peatland development and long-term apparent rates of carbon accumulation (LORCA) were asynchronous in the watershed, suggesting an influence of both latitude and topography (altitude) on the length of the growing season (GGD0). Results show that peat initiation within the three peatlands (respectively ca. 9070, 8400, and 6270 cal BP) was delayed after the deglaciation and that LORCA (respectively 35.5, 15.4, and 9.0 g C m−2 yr−1) decreased from South to North. Peatland development and fen to bog transitions were found to be almost synchronous for the two southernmost sites. The fen to bog transition in the northernmost subarctic site was delayed until the 20th century, owing to the less favorable climatic conditions. This suggests that recent warming has extended the length of the growing season and increased Sphagnum growth enough to potentially influence an ecosystem state-shift as observed in other Subarctic regions of eastern Canada.

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

“…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.…”

“…Although the recent Sphagnum expansion was not supported by detailed 210 Pb 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).…”

“…When considering the current climate warming trend, this ecosystem change coincided with the registered increase in temperature and growing degreedays (>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;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.…”

“…). During this cold climatic episode, northern peatlands in eastern Canada registered important lowering in CAR(Garneau et al, 2014;Magnan and Garneau, 2014;Primeau …”

Paludification reduces black spruce growth rate but does not alter tree water use efficiency in Canadian boreal forested peatlands

“…Moreover, the apparent drying trend could simply reflect an enhanced vertical Sphagnum moss growth, promoted by increasing growing degree days in the last decades (Fig. 5b; Magnan et al 2018;van Bellen et al 2018;Primeau and Garneau 2021;Robitaille et al 2021). The rapid accumulation of organic matter may have exceeded the capacity of adventitious roots to develop higher in the soil profile, compromising the access to oxygen.…”