Carbon storage dynamics in peatlands: Comparing recent‐ and long‐term accumulation histories in southern Patagonia

Abstract

Peatlands have been important terrestrial carbon (C) reservoirs throughout the Holocene, yet whether these ecosystems will become stronger or weaker C sinks in the future remains debated. While surface peat layers (acrotelm) have a greater apparent rate of C accumulation than deeper, millennial‐aged peat (catotelm), it is difficult to project how much more aerobic decomposition will take place before the younger surface cohorts join the older deeper ones. Studies have suggested that warming could lead to weakened C accumulation in peatlands due to enhanced aerobic decay in the acrotelm, which would lead to a slower transfer of peat into the catotelm, if any. Conversely, other studies have suggested increased C accumulation in the acrotelm and thus, larger long‐term C transfer into the catotelm under warming conditions because of greater plant productivity and faster peat accumulation. Improving our predictions about the rate of present and future peatland development is important to forecast feedbacks on the global C cycle and help inform land management decisions. In this study, we analyzed two peat cores from southern Patagonia to calculate their long‐ versus short‐peat C accumulation rates. The acrotelm rates were compared to the catotelm peat C legacies using an empirical modeling approach that allows calculating the future catotelm peat storage based on today's acrotelm characteristics, and thus predict if those recent rates of C accumulation will lead to greater or weaker long‐term C storage in the future. Our results indicate that, depending on local bioclimatic parameters, some peatlands may become stronger C sinks in the future, while others may become weaker. In the case of this study, the wetter site is expected to increase its C sink capacity, while our prediction for the drier site is a net decrease in C sequestration in the coming decades to centuries.

Abrupt Fen-Bog Transition Across Southern Patagonia: Timing, Causes, and Impacts on Carbon Sequestration

“…In 2018 (PAT-18), eight new sites were cored: Beef-Penguin (BP), Mercedes (MP), Jen (JB), Rasmussen (RAS), Ariel (AP), Cura (CP), Pat-Andy-Nat (PAN), and Flarks (FP). Some of the results from cores MP and BP are published (Bunsen and Loisel, 2020),…”

Holocene Carbon Accumulation, Wetness Shifts and Fire History at Three Threatened Peatlands in Carmarthenshire, SW Wales, UK

“…The majority of peatlands initially develop as minerotrophic fens and a large proportion of them transition to ombrotrophic bogs (Loisel and Bunsen, 2020). This shift is commonly referred to as the fen to bog transition (FBT).…”

“…Volcanic activity has also been found to promote the FBT in peatlands proximal to volcanic activity in Patagonia (Loisel and Bunsen, 2020). It is hypothesised that volcanic sulphur dioxide plumes led to enhanced peatland acidification and a subsequent shift to ombrotrophication (Loisel and Bunsen, 2020).…”

“…This focus has come about for two reasons; i) human activities on peatlands, such as burning, cutting and drainage have caused substantial carbon losses (McCarroll et al, 2014;Leifeld and Menichetti, 2018) and ii) there are concerns that predicted atmospheric warming, and shifts in hydrological regimes, might destabilise peatland carbon stocks. The latter could lead to large CO2 emissions and a self-sustaining feedback loop that could accelerate warming (Loisel et al, 2020). This threat that human and climatic forces pose on peatland carbon storage has become a significant global concern in the fight against greenhouse gas climate forcing.…”

“…In light of these concerns, a vast number of studies have investigated peatland carbon accumulation responses to Holocene climatic changes and future projections (Anderson, 2002;Yu et al, 2009;Gallego-Sala et al, 2010;Yu et al, 2012;Charman et al, 2013;Packalen and Finkelstein, 2014;Loisel et al, 2014;van der Linden et al, 2014;Yu et al, 2014;Gallego-Sala et al, 2018;Ratcliffe et al, 2018;Loisel et al, 2020;Beaulne et al, 2021). Although there are still unanswered questions, the general consensus from these studies is that warming during the 21 st century will lead to enhanced carbon accumulation at northern high latitude peatlands (Yu et al, 2012;Charman et al, 2013;Loisel et al, 2014;Yu et al, 2014;Gallego-Sala et al, 2018).…”