Abstract
AbstractDrainage alters the carbon storage and accumulation functions of peatlands, but the long‐term effects of drainage ditches, and their restoration, on peatland development are poorly understood. Timescales of monitoring studies in ditch‐drained and restored peatlands are typically limited to a few years, and occasionally decades. In addition, experimental studies seldom monitor spatial changes in peat structure caused by ditches, despite such changes affecting water flow and water retention in peat. Ecosystem models offer an alternative to experimental studies and can help explain how complex systems such as peatlands may respond to external disturbances. Here we report on a 2‐D application of a peatland development model (DigiBog) to explore how contour‐parallel ditches, and their damming, affect the ecohydrology of peatlands over decades to centuries, using blanket peatlands as a case study. Drainage resulted in the rapid loss of peat due to increased oxic decay. The majority of these losses occurred in the first 100 years after the ditch was created, but water table dynamics were altered even centuries later. Restoration halted the loss of peat and encouraged net peat accumulation, although the amount lost in 100 years of drainage had not been replaced 200 years after the ditch was dammed. Restoration of ditches in sloping peatlands brought about more peat regrowth downslope of the restored ditch than further upslope. Our study demonstrates the potential for spatially distributed ecosystem‐scale models as tools to explore complex spatiotemporal responses to disturbance, and to support land managers in making decisions about peatland drainage and restoration.
Highlights
Peatlands around the world have been subjected to land-use change, with many drained by ditches to improve conditions for forestry, agriculture, peat extraction, and road construction [e.g., Maljanen et al, 2010; Parry et al, 2014; Turetsky et al, 2015; Page and Hooijer, 2016]
Our aim is to explore the potential of using a modeling approach to provide new insights into how drainage ditches and gullies, and their restoration, affect the ecohydrology of peatlands over timescales of decades to centuries, which extends beyond the history of current monitoring and restoration programs
We found that the different resolutions were important drivers of the final size of the peatland, and plan in future to report the implications for peatland development models
Summary
Peatlands around the world have been subjected to land-use change, with many drained by ditches to improve conditions for forestry, agriculture, peat extraction, and road construction [e.g., Maljanen et al, 2010; Parry et al, 2014; Turetsky et al, 2015; Page and Hooijer, 2016]. Some studies have reported water tables in peat adjacent to restored drainage features to be similar to those in pristine sites [e.g., Schimelpfenig et al, 2013; Menberu et al, 2016], others have found hydrological conditions to be intermediate between those of drained and intact sites [e.g., Holden et al, 2011; Wallage and Holden, 2011] These differences may reflect long-lasting changes to peat hydraulic properties caused by dewatering, increased oxic decomposition, and compaction [e.g., Williamson et al, 2017] and inhibit full recovery to the hydrological and C-sequestration functions seen in intact peatlands
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