Peatland management impacts on water quality and biodiversity
Peatland Management Impactson Water Quality and BiodiversityMike Billett/Chris EvansCentre for Ecology & HydrologyEdinburgh/Bangor VNN Peatlands Workshop Leeds 18 Jan 2012
Peatland management issuesEstimated that 18% of UK peatlands arein natural or near-natural conditionremaining affected by change toagricultural land use (40%), severe erosion(16%), peat cutting (11%) andde/afforestation (10%). AMS source with 134 graphite target locations Littlewood, N. et al. (2010). Peatland biodiversity. Report to IUCN UK Peatland Programme
Potential water quality issues•Solutes•Particulates•Dissolved gases•Organic compounds•Inorganic compounds•Concentrations•Fluxes•Simple dilution/concentration effects•Pollutant retention/release (≈ peatland condition)•Timing of transport (“the hydrochemical response”)
Peatland management – effect of burning• Correlative study suggesting higher DOC loss in recently burnt areas• For peat catchments stopping burning in the Peak District would reduce DOC by ~40%• On the same basis increasing burning on the Migneint to Peak District levels would increase DOC by ~30% Yallop and Clutterbuck, 2009.• This is controversial! Experimental data Science of the Total from burnt areas at Moor House (Ward et Environment al., 2007; Worrall and Adamson, 2007) did not show the same DOC response
Peatland management – effect of grazing• Limited data available• Available evidence suggests little impact of moderate grazing on DOC, acidity.• Overgrazing of peatlands may lead to erosion associated with increased nitrate and POC losses• Overall, current evidence considered insufficient to make predictions of change
Peatland management – effect of drainage• Evidence limited and rather inconclusive• Wallage et al. study suggests potential for ~25% reduction in DOC with drain-blocking Wallage et al., 2006. Science of the Total Environment
Peatland restoration - catchment scale research Drained NForested 70 Felled Gaseous C Sampling 60 DIC Downstream Export (g C m-2 yr-1) location DOC 50 POC 40 30 20 10 Drains blocked 0 Pristine Drain Blocked Drained 2 km •Flow Country peatland catchment – initial results suggest higher C fluxes (2006-08) from the drain blocked and drained site compared to pristine •Importance of long-term studies •Also evidence that gully blocking may increase DOC loss (Daniels et al., 2008. Science of the Total Environment )
Peatland restoration - catchment scale research Burning stopped Grazing removed Gullies blocked 20 2002-03 2003-04 18 2004-05 Areal Export of DOC (Ctkm yr ) -1 2005-06 -2 16 14 12 10 8 6 4 2 0 Within Clough Nether Gate Doctors Gate Upper North Upper Gate Red Clough Clough Clough Grain Clough TREATMENT CONTROL Treatments began in 2003 on several Peak district catchments •some early evidence that gully blocking may be reducing the DOC flux? •Importance of long-term studies O’Brien et al. 2008
Particulate organic carbon (POC)Evans et al. (2005): Re-vegetation Catchment Area POC flux Reference Notes Upper North Grain 0.38 km2 95.7 g C m-2 y-1 Evans et al. (2006) Severe gullyreduces sediment production and erosionslope-channel linkages Upper North Grain 0.85 km2 74.0 g C m-2 y-1 Pawson et al. Severe gully (Snake Pass) (2008) erosionHolden et al. (2007): At least 50 times Torside Clough 3.31 km2 11.3 g C m-2 y-1 Rothwell (2006) Calculatedmore sediment from open compared from data in Rothwellto blocked drains (2006) based on 70% organic content) Unnamed micro- 0.0007 km2 92.5 g C m-2 y-1 MG Evans Bare peat catchment near unpublished data catchment Bleaklow summit Unnamed micro- 0.005 km2 3.4 g C m-2 y-1 MG Evans Uneroded catchment near unpublished data catchment Snake summit Lady Clough 1.33 km2 44.8 g C m-2 y-1 Pawson (2008) Measured particulate organic carbon (POC) fluxes from Bleaklow Plateau catchments Billett et al. 2010
Rough Sike story (Moor House NNR)Crisp 1966: Input and output of minerals for an area of Pennine moorland: theimportance of precipitation, drainage, peat erosion and animalsIn 1962-63 Crisp estimated the loss of 5 elements(tonnes yr-1) down Rough SikeNa 3.76K 0.74 55 g C m-2 yr-1Ca 4.46P 0.03N 0.24C 46.0* (*assumes peat contains 50% C)Equivalent to peat loss of 1 cm yr-1 from actively eroding areas (10-20% of catchment)-------------------------------------------------------------------------------------------------------------------------Evans & Warburton 2005: Sediment budget of an eroding peat-moorland catchment innorthern England •In 1997-2001 estimated that 37 tonnes yr-1 of sediment were lost down Rough Sike (≈19 tonnes C) •Significant evidence of re-vegetation since the 1960s Crisp 1966 J. Ecology Evans & Warburton 2005 ESPL
Biodiversity and peatland managementProbability of occurrence of ‘positive’ and ‘negative’ indicator species on peatland as a function of wetness and vegetation height based on Countryside Survey data MultiMOVE model, courtesy of Ed Rowe, Peter Henrys and Simon Smart (other input parameters including pH, nitrogen and climate set to typical blanket bog conditions)
Research evidence base: summaryWith the exception of sediment yield and POC, the evidence is patchy and at times contradictoryScale is hugely importantAre catchment studies of peatland management effects always going to be too site specific and short-term?Should we focus more on process understanding rather than downstream effects?Understanding of effects on biodiversity is poor, although clear links between hydrology and plant species/functional group DOC Effect of drain blocking…….. Time
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