The effect of peatland drainage and rewetting (ditch blocking) on extracellular enzyme activities and water chemistry

Peacock, Mike; Jones, Tim G.; Airey, B.; Johncock, Anna C.; Evans, C. D.; Lebron, Inma; Fenner, Nathalie; Freeman, Chris

doi:10.1111/sum.12138

Cited by 25 publications

(11 citation statements)

References 38 publications

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“…Changes in water table following blocking were variable but very small (<2 cm; Holden et al, ), but rewetting did lead to increases in wet‐indicator testate amoeba suggesting the creation of wetter conditions across the site (Swindles et al, ). However, there was no difference in extracellular enzyme activity in the year following ditch blocking (Peacock et al, ), and Francez, Gogo, and Josselin () noted a lag time in changes to microbial communities following restoration of a harvested raised bog. The lack of strong microbial or hydrological changes could be one reason for the associated lack of effect on DOM composition, as the water table was close to the bog surface despite the presence of open ditches (Holden et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Peat dams are also placed along the reprofiled ditches, creating shallow pools. The experimental site was used to investigate the effects of peatland rewetting on numerous ecological responses such as greenhouse gas emissions (Green et al, ), DOC fluxes (Evans et al, ), hydrology (Holden et al, ), vegetation (Green et al, ), extracellular enzyme activity (Peacock et al, ), and testate amoeba (Swindles et al, ). Further information concerning the study site can be found in Green et al () and includes soil physical and chemical properties, detailed meteorological data, and ditch topographical details.…”

Section: Methodsmentioning

confidence: 99%

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Peatland ditch blocking has no effect on dissolved organic matter (DOM) quality

Peacock

Jones

Futter

et al. 2018

Hydrological Processes

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The globally widespread drainage of peatlands has often been shown to lead to increased concentrations and fluxes of dissolved organic carbon (DOC) in streams and rivers. Elevated DOC concentrations have implications for carbon cycling, ecosystem functioning, and potable water treatment. Peatland rewetting, principally through ditch blocking, is often carried out with the expectation that this will reduce DOC concentrations. Uncertainty still remains as to whether drainage, or its reversal via ditch blocking, will also lead to changes in the molecular composition of DOC/dissolved organic matter (DOM), which have the potential to affect downstream processing and treatability of U.K. drinking water supplies. To investigate this question, we used a replicated experiment consisting of 12 parallel ditches on an upland bog and took samples of ditch water, pore water, and overland flow water for 4 years. After a brief preblocking baseline period, eight ditches were blocked using two methods. A complementary suite of optical metrics, chemical measurements, and analytical techniques revealed that ditch blocking had no consistent effect on DOM quality, up to 4 years after blocking. Where significant differences were found, effect size calculations demonstrated that these differences were small and would therefore have minimal impact upon water treatability. Furthermore, some differences between ditches were evident before blocking took place, highlighting the need for robust baseline monitoring before intervention. Based on our results from a hillslope‐scale experiment, we were unable to identify clear evidence that peatland ditch blocking will deliver benefits in terms of DOM treatability in potable water supplies, although we also did not find any evidence of short‐term deterioration in water quality during the restoration period. We conclude that, although peatland restoration can be expected to deliver other benefits such as reduced carbon loss and enhanced biodiversity, it is doubtful whether it will lead to improvements in drinking water treatability.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Peatland ditch blocking has no effect on dissolved organic matter (DOM) quality

Peacock

Jones

Futter

et al. 2018

Hydrological Processes

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“…For instance, land management practises in these ecosystems often include draining to improve grazing capacity. This practise, leading to a long-term reduction in soil moisture, might provoke a substantial loss of soil C (Peacock et al 2014), as SOM decomposition is progressively stimulated by the changes in soil physical structure.…”

Section: Impacts On Soil Structure and Water Holding Capacitymentioning

confidence: 99%

Sustained impact of drought on wet shrublands mediated by soil physical changes

et al. 2014

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“…Several studies demonstrated that blocking ditches increased the water table in the vicinity (e.g. Armstrong et al, 2010;Cooper et al, 2014;Peacock et al, 2015), although a comparison with an intact peatland in Northern England showed that water tables had not recovered to background levels even six years after blocking ditches (Holden et al, 2011). Water table recovery in blanket bogs is, however, usually small in magnitude, for example 2 cm (Wilson et al, 2010) or 9 cm (Worrall et al, 2007), whereas studies on boreal mires drained for forestry have found that blocking drainage ditches increased the water table in the vicinity by approximately 80 cm (Haapalehto et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Historical peat loss explains limited short-term response of drained blanket bogs to rewetting

Williamson

Rowe

Reed

et al. 2017

Journal of Environmental Management

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This study assessed the short-term impacts of ditch blocking on water table depth and vegetation community structure in a historically drained blanket bog. A chronosequence approach was used to compare vegetation near ditches blocked 5 years, 4 years and 1 year prior to the study with vegetation near unblocked ditches. Plots adjacent to and 3 m away from 70 ditches within an area of blanket bog were assessed for floristic composition, aeration depth using steel bars, and topography using LiDAR data. No changes in aeration depth or vegetation parameters were detected as a function of ditch-blocking, time since blocking, or distance from the ditch, with the exception of non-Sphagnum bryophytes which had lower cover in quadrats adjacent to ditches that had been blocked for 5 years. Analysis of LiDAR data and the observed proximity of the water table to the peat surface led us to conclude that the subdued ecosystem responses to ditch-blocking were the result of historical peat subsidence within a 4-5 m zone either side of each ditch, which had effectively lowered the peat surface to the new, ditch-influenced water table. We estimate that this process led to the loss of around 500,000 m peat within the 38 km study area following drainage, due to a combination of oxidation and compaction. Assuming that 50% of the volume loss was due to oxidation, this amounts to a carbon loss of 11,000 Mg C over this area, i.e. 3 Mg C ha. The apparent 'self-rewetting' of blanket bogs in the decades following drainage has implications for their restoration as it suggests that there may not be large quantities of dry peat left to rewet, and that there is a risk of inundation (potentially leading to high methane emissions) along subsided ditch lines. Many peatland processes are likely to be maintained in drained blanket bog, including support of typical peatland vegetation, but infilling of lost peat and recovery of original C stocks are likely to take longer than is generally anticipated.

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The effect of peatland drainage and rewetting (ditch blocking) on extracellular enzyme activities and water chemistry

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Cited by 25 publications

References 38 publications

Peatland ditch blocking has no effect on dissolved organic matter (DOM) quality

Peatland ditch blocking has no effect on dissolved organic matter (DOM) quality

Sustained impact of drought on wet shrublands mediated by soil physical changes

Historical peat loss explains limited short-term response of drained blanket bogs to rewetting

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