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Effectiveness of Ditch Blockage for Restoring Hydrologic and Soil Processes in Mountain Peatlands



Drained peatlands are a global concern due to alterations of the water and carbon cycle, loss of habitat, and increased fire frequency. However, methods for restoring drained sloping peatlands are limited and poorly tested. Therefore, we measured water table dynamics, CO2 fluxes, and soil properties at four sloping fens that were restored (1–20 years post-restoration) with the installation of small check dams in ditches that had drained the sites for a century. Restoration had a positive effect on water tables, increasing from approximately 45 cm below the surface to approximately 15 cm below the surface during the summers. Restoration also benefited CO2 fluxes, as the mean net ecosystem exchange was greatest in the restored areas (−2.19 g CO2 m−2 hour-1) compared to the unrestored drained areas (−1.28 g CO2 m−2 hour−1), while in reference areas it was −1.74 g CO2 m−2 hour−1. Drainage also caused significant changes to the peat soil including: 25% reduction in soil organic matter (lost between 1.4 to 3.6 kg/m2), increased bulk density, decreased porosity, and reduced saturated hydraulic conductivity. Restoration did not affect these parameters, even 20 years after restoration. This study suggests that although natural water table levels have been reestablished and the process of carbon sequestration improved, the physical properties of the most disturbed, near surface peat soils do not mimic reference conditions 20 years post-restoration.