Subsidence Rates of Drained Agricultural Peatlands in New Zealand and the Relationship with Time since Drainage

The drainage and conversion of peatlands to productive agro‐ecosystems leads to ongoing surface subsidence because of densification (shrinkage and consolidation) and oxidation of the peat substrate. Knowing the ra0te of this surface subsidence is important for future land‐use planning, carbon accoun...

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Bibliographic Details
Published in:Journal of environmental quality 2014-07, Vol.43 (4), p.1442-1449
Main Authors: Pronger, Jack, Schipper, Louis A., Hill, Reece B., Campbell, David I., McLeod, Malcolm
Format: Article
Language:English
Subjects:
Agricultural ecosystems
Agriculture
Carbon
Carbon footprint
Consolidation
Decision making
Drainage
Economic analysis
Environmental accounting
Environmental impact
Farms
Historic
Land use planning
Oxidation
Peat
Peatlands
Shrinkage
Subsidence
Sustainability reporting
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Summary:The drainage and conversion of peatlands to productive agro‐ecosystems leads to ongoing surface subsidence because of densification (shrinkage and consolidation) and oxidation of the peat substrate. Knowing the ra0te of this surface subsidence is important for future land‐use planning, carbon accounting, and economic analysis of drainage and pumping costs. We measured subsidence rates over the past decade at 119 sites across three large, agriculturally managed peatlands in the Waikato region, New Zealand. The average contemporary (2000s–2012) subsidence rate for Waikato peatlands was 19 ± 2 mm yr−1 (± SE) and was significantly less (p = 0.01) than the historic rate of 26 ± 1 mm yr−1 between the 1920s and 2000s. A reduction in the rate of subsidence through time was attributed to the transition from rapid initial consolidation and shrinkage to slower, long‐term, ongoing oxidation. These subsidence rates agree well with a literature synthesis of temperate zone subsidence rates reported for similar lengths of time since drainage. A strong nonlinear relationship was found between temperate zone subsidence rates and time since initial peatland drainage: Subsidence (mm yr−1) = 226 × (years since drained)−0.59 (R2 = 0.88). This relationship suggests that time since drainage exerts strong control over the rate of peatland subsidence and that ongoing peatland subsidence rates can be predicted to gradually decline with time in the absence of major land disturbance.
ISSN:0047-2425
1537-2537
DOI:10.2134/jeq2013.12.0505