A Low-Cost Multiproxy Framework for Assessing the Quality of Carbon Loss from Degraded and Restored Post-Agricultural Lowland Peatlands

Lowland peatlands are a globally significant carbon store; yet they are intensively used in agriculture and grazing. Long-term peat drainage has led to an imbalance in their ability to sequester carbon, making them a potential C source, as opposed to a long-term C sink, and leading to irreversible loss of ancient carbon stored in the deeper parts of the peat profile. This study investigates the sources and dominant pathways of carbon loss from previously drained, post-agricultural lowland peatlands, with the aim of developing practical, low-cost approaches to assess the quality of carbon exported from these systems. Temporal dynamics of dissolved organic matter (DOM) and its aromaticity are used as proxies to detect changes in carbon cycling in response to a range of rewetting histories and peat restoration strategies.

The quality and composition of DOM and gaseous carbon exchange were monitored across five lowland peatland sites spanning intact, drained, and restored systems. Monthly water sampling (Oct 2024–Oct 2025) was combined with continuous water-table measurements and in-situ CO₂–CH₄ flux monitoring. Pore-water DOC concentration, SUVA²⁵⁴, and related optical indices were used to assess DOM quantity and aromaticity.

At sites exhibiting minimal peat degradation and longer rewetting durations, pore-water dissolved organic carbon (DOC) concentrations were not associated with elevated SUVA²⁵⁴ values, indicating that DOC exported from these systems is predominantly labile rather than recalcitrant. In contrast, site outlets (ditches) showed disproportionately high SUVA²⁵⁴ relative to DOC concentrations, suggesting enhanced leaching of aromatic carbon compounds, particularly from more intensively degraded sites. Ongoing radiocarbon analyses will further constrain carbon turnover times and allow the observed fluxes to be interpreted in the context of carbon age and stability.