Tephra deposits and carbon accumulation in drained Icelandic peatlands

The co-occurrence of active volcanism and severe soil erosion sets Icelandic peatlands apart from peatlands of volcanic regions elsewhere. Located in an active volcanic environment and often in close vicinity to glacial outwash plains and eroded drylands, they display a wide range in mineral and organic content. Mineral material of volcanic nature as distinct tephra layers deposited during volcanic eruptions, but also in the form of recurring fluxes of windborne dust from aeolian source areas are often well preserved in Icelandic peatland soils. Carbon rich subsoil layers are frequently found below more mineral surface soil layers, reflecting destabilization of the environment owing to the onset of anthropogenic influence after the human settlement of Iceland c. 870 AD, which led to widespread vegetation destruction, soil degradation and erosion.

Despite extensive areas of peatlands worldwide being located within active volcanic regions, the interactions between tephra deposits from volcanic eruptions and peatland carbon (C) dynamics are still poorly understood. Various previous studies have shown that tephra deposits may induce shifts in vegetation and the hydrology of peatlands. By that, they may also affect C accumulation. However,  questions remain as to how mineral deposits within these soils, in the form of distinct tephra or aeolian material from eroded dryland soils, impact the C accumulation. Thus, Icelandic peatlands offer a unique opportunity to investigate the effect of tephra deposits and anthropogenic impact on C dynamics in peatlands.

We present a study on C accumulation and C decomposition of disturbed peatlands in Iceland over time. To determine how distinct tephra deposits impact C dynamics of peatland soils, we focus on C accumulation in soil layers right above and below tephra layers.