24-6 The effects of hydrologic changes on carbon accumulation in Zurich Bog, New York during the Holocene

Session: Lake Sedimentary Records of Past Climate and Environment (Posters)

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Peatlands are important carbon sinks that play a crucial role in the global carbon cycle. Understanding how peatland carbon sequestration operates is essential for predicting ecosystem responses to future climate change. Peatland evolution is strongly influenced by local hydrological conditions, yet the relationship between water level and carbon accumulation in temperate peatlands remains poorly understood. This study examines how variations in water supply, driven by changes in precipitation and overland flow, affect carbon accumulation at Zurich Bog, a 2.6 km² wetland complex of pond, fen, bog, and forested swamp within the Ontario Lowlands during the Holocene.

We collected a 2.04-m-long sediment core from the bog margin spanning the late deglaciation to present. The core preserves three lithofacies representing distinct depositional environments: basal proglacial clay, herbaceous peat, and woody peat. We applied a multi-proxy approach, including smear-slide analysis, loss-on-ignition (LOI; % organic matter, carbonate, lithogenous material), magnetic susceptibility (MS), and high-resolution m-XRF elemental analysis to characterize these lithofacies. The basal gray clay is dominated by lithogenous material (~95%) and records site inundation by Glacial Lake Iroquois until ~13 ka BP. Herbaceous and woody peat intervals record contrasting hydrological and sedimentary conditions that influenced carbon accumulation. Herbaceous peat intervals are characterized by high % organic matter (70-80%), low magnetic susceptibility, and low Ti, K and lithogenous content (~20%), indicating minimal detrital input and predominantly organic accumulation. These intervals are also associated with Frustulia and Navicula, diatom taxa typical of organic-rich, low-energy peatlands. In contrast, the six woody peat intervals (up to 20-cm thick) that we identified exhibit lower % organic matter (30-60%), elevated MS, higher Ti, K and lithogenous content (40-70%; e.g., quartz, chlorite, muscovite), reflecting increased minerogenic input to the basin during overland flow events. Benthic and epiphytic diatoms (Meridion, Diploneis, Stauroneis) occur in the woody peat and tolerate alkaline to neutral pH waters and fluctuating nutrient concentrations. Together, these indicators demonstrate variations in water-table and detrital input exerted a first-order control on peat composition and carbon accumulation at Zurich Bog during the Holocene. Additional radiocarbon ages will help constrain the timing of overland flow events into the basin.

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