Trajectories of ecosystem change in restored blanket peatlands.

Peatlands provide a range of ecosystem services but are sensitive to changes in climate and land-use, and many peatlands globally are degraded. We analyse a large-scale, unique and diverse dataset, collected over 15 years, as part of major landscape scale blanket peat restoration projects in the south Pennines, UK. Trajectories of ecosystem change after restoration were assessed by measuring key ecosystem responses including: vegetation cover and indicator species; water table, runoff, and water quality. The reactions of these metrics vary in their behaviour, both in the timing of first response and the rate of change towards a new stable state. Re-establishment of vegetation is a key driver in rapidly reducing particulate carbon loss and attenuating stormflow, while over time biodiversity is improved by the return of native species, and water tables gradually rise. The phasing of these ecosystem service responses indicates that there are different characteristic timescales for the improvement of peatland functions, driven by both surface and subsurface processes. The rapid establishment of vegetation cover over two years, and its importance in improving a broad range of functions, signify it as a key milestone for reporting project success within typical funding timeframes. This study supports the adoption of Lime-Fertiliser-Seed-Mulch restoration on eroding blanket peatlands globally. The trajectories developed are important to help guide practitioners of ecological restoration. Better understanding of the dynamics underpinning the slower response times of subsurface hydrological and biogeochemical function is identified as a key knowledge gap. An understanding of the limits of ecosystems recovery is important when target setting for restoration projects, especially where attaining pristine conditions is unachievable.

Contrasting controls on arsenic and lead budgets for a degraded peatland catchment in Northern England.

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 ± 21.3 gPb ha(-1) y(-1) and 60.4 ± 10.5 gAs ha(-1) y(-1)), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters.

Storage and behavior of As, Sb, Pb, and Cu in ombrotrophic peat bogs under contrasting water table conditions.

Concentration depth profiles and inventories of solid-phase As, Sb, Pb, and Cu were determined in ²¹°Pb-dated cores from an ombrotrophic peat bog in northwest England. Cores were collected from the peat dome and adjacent to an eroding gully. Down-core distributions of As, Sb, Pb, and Cu in the dome core are almost identical. The water table is close to the dome surface with only short-term draw-down. Under these conditions, As, Sb, Pb, and Cu are immobile, allowing the reconstruction of trends in historical contaminant deposition. The peak in atmospheric deposition of As, Sb, Pb, and Cu (4.59, 2.78, 147, and 26.7 mg m⁻² y⁻¹, respectively) occurred during the late 19th century. Stable Pb isotope ratios reveal that Pb deposition during this period was from indigenous and foreign sources. The mean water table is much lower at the gully edge, and there are pronounced interannual fluctuations. These conditions have not affected the integrity of the Pb and Cu records but have caused postdepositional mobilization and redistribution of As and Sb. Cumulative inventories show significant loss of As and Sb at the gully edge site. Long-term water table draw-down in ombrotrophic peat bogs has the potential to alter the geochemistry and fate of previously deposited As and Sb.

Peat soils as a source of lead contamination to upland fluvial systems.

Upland peat soils are generally regarded as effective sinks of atmospherically deposited lead. However, the physical process of erosion has the potential to transform peat soils from sinks to sources of lead contamination. Lead input and fluvial lead outputs (dissolved+particulate) were estimated for a contaminated and severely eroding peatland catchment in the southern Pennines, UK. Lead input to the catchment is 30.0+/-6.0gha(-1)a(-1) and the output from the catchment is 317+/-22.4gha(-1)a(-1). Suspended particulate matter accounts for 85% of lead export. Contaminated peat soils of the catchment are a significant source of lead to the fluvial system. This study has demonstrated strong coupling between the physical process of erosion and the mobilization of lead into the fluvial system. The process of peat erosion should therefore be considered when estimating lead outputs from peatland catchments, especially in the context of climate change.

Scale-dependent spatial variability in peatland lead pollution in the southern Pennines, UK.

Increasingly, within-site and regional comparisons of peatland lead pollution have been undertaken using the inventory approach. The peatlands of the Peak District, southern Pennines, UK, have received significant atmospheric inputs of lead over the last few hundred years. A multi-core study at three peatland sites in the Peak District demonstrates significant within-site spatial variability in industrial lead pollution. Stochastic simulations reveal that 15 peat cores are required to calculate reliable lead inventories at the within-site and within-region scale for this highly polluted area of the southern Pennines. Within-site variability in lead pollution is dominant at the within-region scale. The study demonstrates that significant errors may be associated with peatland lead inventories at sites where only a single peat core has been used to calculate an inventory. Meaningful comparisons of lead inventories at the regional or global scale can only be made if the within-site variability of lead pollution has been quantified reliably.