Hydrological and geochemical responses of a maritime peatland to fire disturbance: preliminary multi-proxy results from eastern Canada

Peatland hydrology strongly regulates ecosystem functioning, carbon storage, and vulnerability to disturbance. Although maritime peatlands along the Gulf of Saint Lawrence (eastern Canada) are generally considered fire-resilient due to high atmospheric moisture, recent severe fire seasons in surrounding boreal forests highlight the need to better understand how fire influences peatland hydrological and biogeochemical dynamics. Such understanding is essential for interpreting long-term palaeoecological records and assessing peatland sensitivity to ongoing climate warming.In this multi-proxy study, we combine traditional palaeoecological proxies (testate amoebae, charcoal, pollen, and plant macrofossils), with geochemical analyses (XRF and FTIR) to evaluate the impacts of local and regional fires on a maritime raised bog near Baie-Johan-Beetz (Québec). We present preliminary high-resolution results from a short peat monolith (BJB-03) covering the last ~1100 years. The record captures distinct ecological and geochemical shifts, including lichen-Sphagnum transitions, changes in peat accumulation rates, and intervals of increased presence of macrocharcoal particles associated with variations in elemental composition, carbon content, and peat decomposition. Using FTIR, a novel method in peatland fire studies, we aim to detect highly oxidised, presumed pyrogenic carbon and to quantify the relative redox state of peat, linking these signals to disturbance events recorded in the sequence.The monolith provides a detailed archive of environmental change during the last millennium, including the period surrounding the well-documented 2013 regional fire event. These preliminary results constitute the first stage of a broader project reconstructing fire–hydrology interactions over the past 7500 years in this region of Canada.The study was supported by the National Science Center of Poland (no. 2024/35/O/ST10/02903).