Water quality impacts of bare peat revegetation with lime and

fertiliser application.

A.G. Stimsona, T.E.H. Allotta, S Boultb, M. G. Evansa, M Pilkingtonc Nicole Hollanda

aUpland Environments Research Unit, School of Environment, Education and

Development, The University of Manchester, Oxford Road, M13 9PL, United Kingdom.

bSchool of Earth, Atmospheric and Environmental Science, University of Manchester,

Oxford Road, Manchester, M13 9PL, UK.

cMoors for the Future Partnership, Moorland Centre, Fieldhead, Hope Valley, S33 7ZA

Highlights

4-year dataset covers peatland revegetation with lime and fertiliser application.

Impacts on run-off waters to headwater fluvial systems monitored.

No lasting impact on Dissolved Organic Carbon, but temporary suppression

evident.

Maximum Dissolved Organic Carbon suppression recorded is 50% of control

values.

Initial high phosphate export suggests application regime may need adjustment.

1

Abstract

Loss of peatland vegetation is a global problem with negative consequences for the quality

of catchment drainage waters. Vegetation can be lost through a combination of human and

natural processes, leading to areas of exposed bare peat frequently accompanied by loss of

surface moisture due to drainage or gullying. Waters draining such degraded peatlands are

likely to have increased levels of dissolved organic carbon (DOC) and other nutrients,

which can adversely impact the global climate, drinking water supplies and freshwater

ecology. Consequently peatland revegetation efforts have become widespread.

This paper presents results from a four-year study conducted to monitor the water quality

impacts of a bare peat revegetation approach, which used landscape scale application of

lime and fertiliser to encourage a grass nurse crop. This study considers an area of

severely degraded blanket peat in the UK uplands, with large areas of bare peat prior to

revegetation and provides the largest field dataset to date on the effects of this method on

catchment run-off waters. Despite concerns that liming could increase DOC

concentrations, the revegetation method is not shown to have this effect over the time

period, and interestingly results in short term periods of suppression. The mechanism for

this novel and unexpected finding merits further investigation and results in reduced DOC

concentration, by up to 14 mg/l or 50 % of control values, combined with periods of

reduced colour carbon ratios. The data show that other nutrients were largely unaffected

although rates of phosphate (PO43-) export were above recommended levels in the first year

of application, suggesting initial phosphorus (P) application rates may require adjustment.

Further investigation is required to consider the longer term effects of this restoration

method as the vegetation matures.

Keywords: Peatlands, Restoration, DOC

2

1. Introduction

Globally, peatlands cover an area of approximately 4.4 million km2 or 3% of the earth’s

land surface (Limpens et al., 2008; Yu et al., 2010). Many of these peatlands have lost

vegetation through a complex interplay between human (grazing, agriculture, drainage,

burning, mining, deforestation) and natural (climate changes, wildfire) influences

(Chapman et al., 2003; Tallis, 1998; Turetsky et al., 2002; Wösten et al., 2006). Loss of

vegetation is also frequently accompanied (and hastened by) reduced surface moisture, due

to artificial drainage, or gullies caused by increased erosion of unprotected surfaces,

leading to lowered water tables. The loss of vegetation from peatlands is a global problem

with negative consequences for water quality and other ecosystem services (Kimmel and

Mander, 2010). As a result there has been increasing effort to implement and evaluate

methods of revegetation (Page et al., 2009; Parry et al., 2014; Rochefort and Lode, 2006),

including several approaches where lime and / or fertiliser are applied. Liming may be

used as part of revegetation programmes as bare peat surfaces, especially those with

lowered water tables, are less able to neutralise atmospheric acid deposition (Gorham et

al., 1987) resulting in pH levels below those suitable for plant reestablishment.

Fertilisation may also be employed as bare peat soils are commonly low in major nutrients

especially phosphorous (P) and potassium (K) required for plant growth (Aro et al., 1997;

Finér and Laine, 1998).

Improving water quality is one key driver behind peatland revegetation programmes.

Catchment run-off from bare peat may have higher levels of dissolved organic carbon

(DOC) due to physical erosion and solution of particulate material, or increased DOC

associated with lowered water tables (Bussel et al., 2010). High levels of DOC have

3

implications for atmospheric carbon levels due to fluvial conversion of DOC to carbon

dioxide (CO2) (Limpens et al., 2008) and the cost of removing DOC during drinking water

treatment (Ledesma et al., 2012; Wallage et al., 2006). Additionally healthy wetlands play

a role in limiting the release of other nutrients responsible for eutrophication (Scholz and

Trepel, 2004). Whilst revegetation may result in long term water quality improvements is

it also important to understand how the waters of the large scale chemical additions

associated with lime and fertiliser application impact catchment drainage waters in the

short to medium term. For example several studies have linked liming to increased DOC

concentrations (Andersson and Nilsson, 2001; Grieve, 1990a, 1990b), whilst fertiliser

dosing could result in high fluvial concentrations of Nitrogen (N) or P species if levels

applied are greater than plant uptake (Baligar et al., 2001; Di and Cameron, 2002;

Mcdowell et al., 2001). Several studies have considered the effects of peatland

revegetation programmes accompanied by lime and / or fertiliser application. However

these have largely focused on plant growth, CO2 release rates or soil pore waters (Biasi et

al., 2008; Caporn et al., 2007; González and Rochefort, 2014; Qassim et al., 2014; Salonen

and Laaksonen, 1994), with little work carried out on the landscape scale water quality

implications.

This study presents four years of water chemistry data from peatland catchment drainage

waters, during a period in which lime, fertiliser and seed was applied to encourage

peatland revegetation. The catchments are located on the Kinder Scout plateau, an area of

degraded upland blanket peat in the South Pennines, UK. Kinder Scout and surrounding

blanket peats in the South Pennine area represent an area that has suffered from major

peatland degradation (Evans and Warburton, 2007). This includes considerable gullying

(Tallis, 1998), large areas of bare peat (Anderson and Radford, 1994), and water table

4

drawdown (Daniels et al., 2008). The area also has a legacy of substantial industrial

pollution, and sulphur dioxide (SO2) in particular has been associated with the large scale

disappearance of sphagnum species (Ferguson et al., 1978). This study aims to establish

the short term effects of landscape scale applications of lime and fertiliser to encourage

peatland revegetation on the nature of catchment drainage waters. Firstly it seeks to

determine the flux of lime (CaCO3) and NPK (N:P2O5:K2O) fertiliser into water courses.

Secondly it aims to assess the secondary effects of these applications, and the re-

establishment of vegetation on water colour and DOC concentration. The water quality

data produced should assist land managers in designing future restoration programmes,

and allow a fuller assessment of the impacts of the restoration method on peatland

ecosystem services.

5

2. Methodology

To meet the objectives of this study the water chemistry of run-off waters from four micro

catchments (Figure 1, Table 1) consisting of a bare peat control catchment and three

catchments undergoing bare peat revegetation with lime and fertiliser application, is

considered over a four year period, between December 2010 and January 2015.

Figure 1: Study area – Kinder Plateau, South Pennines, UK. Sampling locations mark the outflow from each catchment. Catchment codes are further explained in the text and Table 1.

6

2.1. Study catchments: water sampling and revegetation treatment

Water samples were collected from catchments C, R1l and R2s on an approximately

fortnightly basis between 1/12/2010 and 5/1/15 (Table 1). Water samples were collected

from an additional catchment (R3s) between 15/10/11 and 5/1/15. Water samples were

collected from water flowing over weirs constructed at the catchment outlets and were not

collected when there was no flowing water. In total there were 103 visits where samples

were taken from at least one of the four catchments.

Prior to revegetation all the catchments contained large areas of bare peat. No revegetation

activities took place within catchment C to allow it to be used as a control. The same

regime of lime, fertiliser and seed application to encourage plant growth was applied to the

three catchments in this study undergoing revegetation. The method involved applying

lime to raise pH followed by an application of NPK (N:P2O5:K2O) fertiliser, and a nurse

grass seed mixture comprising agricultural and amenity grasses, locally collected grass

(Deschampsia flexuosa) and dwarf shrubs (Calluna vulgaris and Erica tetralix). The nurse

grasses were selected for their ability to germinate rapidly and allow native peatland

vegetation to establish over a longer timespan. The application regime comprised an

initial application in the first year, followed by two years of maintenance applications

(Table 1, Table 2). Seed was applied during the first year of application only, whilst lime

was applied (at the same rate) for all application years. NPK fertiliser formulated

according to N:P2O5:K2O ratios, was applied at different rates for the initial and

maintenance applications. The initial fertiliser application contained more P to encourage

root growth, whilst the maintenance application contained more K to encourage flowering

(see Table 2 for product formulation and application rates). The fertiliser applied was bulk

7

purchased by the Moors for the Future partnership who reported that it consisted of a

mixture of potassium chloride (KCl) and di-ammonium phosphate ((NH4)2 HPO4)

8

Catchment characteristics Years with lime and fertiliser applications Water samplesb

Codea Type Area (m2) 2011 2012 2013 2014 Total number

Sampling period

C (F) Control(Bare Peat) 7008 x x x x 93 2010-2015

R1l(N) Revegetation 7096 x 101 2010-2015R2s(O) Revegetation 4468 x 95 2010-2015R3s(B) Revegetation 4982 x x 57 2011-2015

a Subscripts l= large catchment, s= small catchment, letters in brackets are the original codes used for sample collection see Stimson (2016).bSampling took place at approximately fortnightly intervals. At catchment R3s sampling started later and only covered two years of lime and fertiliser application (one initial and one maintenance).

Table 1: Details of the study catchments and water samples taken.

9

2.2. Discharge Measurement

V notch weirs were installed at all catchments and adjacent stage loggers (Skye / Tru-track

WT-HR 1000) recorded water level at 10 minute intervals. Stage figures were adjusted for

drift through the use of fortnightly manual stage board measurements. Stage was then

converted into discharge in litres per second, using the stage / discharge relationship for

each weir.

2.3. Laboratory Methods

Water samples were returned to the laboratory and filtered at 0.45 µm using glass

microfibre or cellulose acetate syringe filters and stored in the dark below 4°C prior to

analysis. To meet the study objectives laboratory measurements of Ca2+, NO3-, PO4

3- and

K+ ion concentrations were taken alongside colour (absorbance at 400nm - Abs400) and

DOC concentration (measured from Dec 2010 to March 2011 and end Sept 2012

onwards). Cations were measured using ICP-OES and anions using Ion Chromatography

(IC). Absorbance was measured using a spectrophotometer (Hach DR 5000) and DOC

using a TOC-V analyser (Shimadzu). The majority of samples were analysed within two

weeks for absorbance, three weeks for DOC, four weeks for IC and eight weeks for ICP-

OES (samples for ICP-OES analysis were acidified following filtration using ultrapure

HN03). Calibration standards (8ppm IC and ICP-OES and 40ppm TOC) were run between

every 10 samples with results rejected if variance exceeded 10%. Lower detection limits

were 0.5ppm for the TOC-V analyser and 0.05ppm for IC and ICP-OES (except NO3- at

10

0.1ppm). Blank samples (deionized water passed through a 0.45 μm Whatman G/F

membrane filter) were also run to confirm that filtration did not affect the chemical

determinands measured.

2.4. Lime and NPK fertiliser mass balances

To enable ecosystem impacts and the likely mechanisms of water quality changes to be

established, mass balance calculations were performed for four elements representing

applications of lime and NPK fertiliser. Estimation was performed by applying equation

(1).

L=∑i=1

n

CQ(1)

In equation (1) L represents the total load in kg, C an individual point concentration

measurement in mg/l, whilst Q represents the total discharge in megalitres for a period

starting and finishing half way between each concentration measurement. Mass balances

were calculated for the large (R1l) and one small (R3s), revegetation catchments for the

first two years of lime and fertiliser application. The time period chosen lasted from the

first day of application, until concentrations dropped below 3 mg/l, with this figure

selected as it represented the upper limit of the post application baseline concentration

across the four ions measured (Figure 3).

To calculate retention and export rates, catchment application rates were calculated for

each element (Table 2).

11

Element Product Formulation

Application rate(kg / ha)

Amount of element in product (%)a

Catchment application (kg)

R1l R3s

I M I M I M I M

CalciumLime: CaCO3 (98%)MgCO3 (1%)Si2 (1%)

1000 1000 39 39 278 278 196 196

NitrogenNPK Fertiliser N:P2O5:K2OI %: 11:33.5:16M %: 14.5:21.5:21.5

361 278 11 15 28 29 20 20

Phosphate 361 278 22 14 56 28 40 20

Potassium 361 278 13 18 34 35 24 25

aCalculated based on molecular weight. I = Initial application (1st year) M = Maintenance application (2nd and 3rd years)

Table 2: Calculation of element application rates for catchments R1l and R3s.

2.5. Water colour and DOC modelling and statistical analysis

As DOC was not measured for the entire monitoring period, time series of absorbance at

400 nm (Abs400) covering the full period were converted into modelled DOC based on the

relationship between measured DOC data and absorbance at 400 nm (Abs400). Abs400 is

used as a proxy for DOC (Wallage et al., 2006; Worrall et al., 2006), with the relationship

used in this study shown in equation (2) and Figure 2.

DOC=1.2092|¿400|+4.8984 ¿ (2)

Figure 2: Relationship between absorbance at 400 nm (Abs400) and DOC concentration for 205 samples where DOC was measured.

DOC concentration commonly follows a seasonal pattern, peaking in late summer / early

autumn (Koehler et al., 2009), and is also subject to synoptic patterns (i.e. drought or large

storm events). Therefore to allow the impacts of the revegetation method to be isolated

values of water colour and DOC for catchments R1l, R2s and R3s were calculated relative to

catchment C. Where periods of deviation from control associated with lime and fertiliser

application were identified, these were tested against unaffected periods to determine if the

differences were statistically significant. Time periods classed as “impacted” of duration

100 and 150 days were selected, as this best captured affects across the four datasets and

different years of application. Shapiro-Wilk tests for normality and normal probability

plots (see supplement Table 5S), showed three of the eight datasets tested to have

potentially non-normal distributions. As a consequence, both parametric (students t-test)

and non-parametric (Mann-Whitney U) tests for statistically significant differences were

performed.

A sensitivity analysis was also performed on the modelled DOC data for revegetation

catchments R1l and R2s during the period of maximum deviation from the control in 2011,

as data from catchment R3s indicated that deviations could also affect the relationship

between colour and carbon. Comparison of modelled and actual colour carbon ratios for

catchment R3s (Figure 5b) showed that lime and fertiliser applications caused a short term

decline in the colour carbon ratio. In the sensitivity analysis, the maximum decline in the

colour carbon ratio (0.23) from catchment R3s was subtracted from the colour carbon ratio

predicted from the Abs400:DOC relationship shown in Figure 2. Modelled DOC was then

recalculated for catchments R1l and R2s in the first year of application, using these

adjusted colour carbon ratios.

14

3. Results and discussion

3.1. Direct effects of lime and fertiliser on catchment drainage waters

3.1.1. Concentration and export summary

Direct effects of the lime and fertiliser applications were seen in run-off waters from

revegetation catchments R1l, R2s and R3s, through short term elevated concentrations of

Ca2+ and PO43- for all applications. K+ shows similar patterns but is not as consistent,

whereas NO3- shows little response (Figure 3). Concentrations at catchment C (control)

showed no notable peaks associated with lime and fertiliser applications and mean values

(Supplement Table 1S) were comparable with similar peatland systems, see Stimson

(2016). When mass balances from the revegetation catchments are considered (Table 3,

Supplement Figure 1S), the evidence suggests that apart from P in the first year of lime

and fertiliser applications, most of the products applied remained within the catchment for

the duration of the monitoring period.

Ca2+ had the most consistent response to lime and fertiliser application and showed peaks

in all years when applications occurred at the revegetation catchments. Concentrations

prior to the first application were generally below 1 mg/l in keeping with the average for

control catchment C (see Supplement Table 1S). Following the first application,

catchments R1l and R2s exhibited peaks of 28 and 25 mg/l respectively, followed by

reduced peaks in subsequent years. Catchment R3s had lower peaks of 6 and 9 mg/l, for

the applications in 2013 and 2014 respectively. At the three revegetation catchments

periods of elevated concentration lasted for between 100 and 200 days, with concentrations

15

then returning to higher baseline of between 1 - 3 mg/l. Catchment C had the lowest

average concentration over the period, with few points above 1 mg/l and no peaks that

occurred at the same time as applications.

PO43- had the most dramatic response to applications, and showed very large peaks relative

to baseline concentrations, in the first application year at catchments R1l, R2s and R3s .

Concentrations in revegetation catchment run-off prior to the first application, were

comparable with the control average at around 1 mg/l. Peaks in the first year were 233,

202 and 158 mg/l, and in the second year 12, 10 and 23 mg/l at catchments R1l, R2s and R3s

respectively. The second year peaks were an order of magnitude less than those in the first

year, but still a substantial variation from the control. Periods of elevated concentrations

were comparable with Ca2+. Baseline concentrations following applications were slightly

above the control, but to a minor level compared to the maximum concentrations. Control

catchment C behaved in a similar way to Ca2+, although the mean value was slightly higher

at 3 mg/l.

K+ had a similar response to Ca2+ in the first year of application. In subsequent years there

was evidence of a response to lime and fertiliser application, but this is less consistent

across the revegetation catchments and of a lower magnitude. Revegetation catchment

concentrations prior to the first application were comparable with the control average of

below 1 mg/l. Peaks in the first year were 18, 18 and 10 mg/l, at catchments R1l, R2s and

R3s, respectively.

16

Figure 3: Time series for the study period showing concentrations of Ca2+, NO3-, PO4

3− and K+ ions in the fluvial discharge from the 3 revegetation catchments and control catchment C. Vertical lines mark the start of lime and fertiliser applications in a given year. Time is from day 0 to 1496 (01/12/2010 to 05/01/2015).

17

Catchment R2s showed a peak of 15 mg/l in response to the second year of application.

Peaks for subsequent years at the other catchments were all below 5 mg/l. The first period

of elevated concentrations was of similar duration to Ca2+, but subsequent peaks generally

represent single high points. All baseline concentrations were comparable with the control

catchment, which had an average value below 1 mg/l and no peaks occurring at the same

time as applications.

Catchment Year Element

Amount exported by end of period (%)

Length of period (days)

Maximum Iona

Concentration (mg/l)

2011Calcium 5 70 28

R1l Phosphorus 81 70b 233Potassium 14 49 18

2012Calcium 2 48 11

R1l Phosphorus 3 76 12Potassium 6 22 5

2013Calcium 3 146 6

R3s Phosphorus 40 130 158Potassium 10 21 10

2014Calcium 3 152c 9

R3s Phosphorus 8 173 23Potassium 6 133 4

aIons measured: Calcium Ca2+, Phosphorus PO43-, Pottasium K+ bstops due to gap in discharge data with concentration at 45.6 mg/l cend

of available concentration data with concentration at 4.7 mg/l

Table 3: Mass balances for catchments R1l and R3s for lime and fertiliser applications with period lasting until concentration data drops below 3 mg/l. Mass balances for NO 3

- are not shown as this showed no notable peaks in these catchments. See also supplement (Figure 1S) for a graphical representation of change over time of cumulative percentage export of P and PO4

3- concentrations.

Control catchment C had three notable outlying high points for Ca2+ and one each for PO43-

and K+, and all peaks occurred between 64 and 115 days following applications at the

18

revegetation catchments. It is possible that these could be accounted for by wind-blown

lime or fertiliser, although the fact that peaks occurred at different times for different

determinands provides an argument against this. The peaks may also represent noise in the

data, however the key point to stress is that they were of lower magnitude and duration

(three single points and one pair) than the those at the revegetation catchments, and were

not associated with an immediate response to lime and fertiliser applications.

NO3- concentration showed minimal response to applications, with a single peak at

catchment R2s of 22mg/l in the second year of application, the only notable difference

between the revegetation and control catchments. The mean value across all four

catchments was between 1 and 2 mg/l.

3.1.2. PO43- dynamics

PO43- concentrations at the revegetation catchment outlets in the first year of application are

of concern as they considerably exceed recommended drinking water quality standards

(Vega et al., 1998), and levels recommended to avoid eutrophication (White and

Hammond, 2006), suggesting adjustments to the application regime are required The peak

concentrations of PO43- in this study of 157 – 232 mg/l, convert to 76 - 106 mg/l of P. This

is substantially in excess of maximum P concentrations (up to 2-3 mg/l) commonly found

in agricultural drainage waters where fertiliser has been applied (i.e. Sims et al., 1998),

although values of up to 30 mg/l are reported following manure applications (Smith et al.,

2001). There is also evidence that application of fertiliser to organic soils results in higher

rates of catchment P export. Miller (1978) reports one instance of average PO4-P

19

concentrations of 18.2 mg/l in drainage waters, whilst leaching rates of P equating to 89%

of fertiliser application, from organic soils have been found (McDowell and Monaghan,

2014). Additionally a previous study of NPK fertiliser applied to a re-seeded blanket bog,

reports maximum values of 13 mg/l P (Williams and Young, 1985).

This area of peatland has received high loads of N deposition in the past, and recent

evidence suggests the system may remain N saturated (Wright and Alewell, 2001). Where

N deposition is high, the system is likely to be P limited (Lund et al., 2009). Whilst the

high export of P could be considered at odds with this, when the revegetation catchments

received their first application of P they contained large areas of bare peat, where plants

would not have been able to utilise the fertiliser. By the second year of application

vegetation had become established and so it is likely more P was utilised. This effect

could explain why the difference between export rates for the initial and maintenance

applications, is greater than the reduction in P application rates between the two. In the

second year of lime and fertiliser additions the P application and export rate is comparable

with that recorded in the study by Williams and Young (1985).

Export rates for Ca and K were an order of magnitude lower than P in the first year of

application, and one explanation that could explain this is the possible link between high

levels of sulphate ions (SO42-) in South Pennine peats, as a consequence of legacy

atmospheric pollution (Daniels et al., 2008), and the release of P due to competition

between SO42- and PO4

3- ions for anion sorption sites (Caraco et al., 1989). Calculations

based on the aerial application rates (see Supplement Table 6S), show that fertiliser

directly applied onto the weir pools could also produce P concentrations of similar

magnitude to those observed here, however this does not explain the high P export rates,

20

the lower concentrations in the second year of application, or why mean and maximum

concentrations of Ca2+, K+ and NO3- are not in proportion to P when input rates are

considered.

3.2. Impacts on colour and DOC in catchment drainage waters.

Measurements of colour and DOC concentration from the run-off waters of the the three

revegetation catchments, did not appear to indicate long term changes relative to the bare

peat control catchment (Figure 4, Supplement Table 2S). However, statistically significant

(P<0.05, see Supplement Table 4S) impacts on water colour and modelled DOC associated

with lime and fertiliser applications, were seen in run-off waters from catchments R1 l, R2s

and R3s, with periods of short term suppression relative to the control (Figure 4). Water

colour (light absorption at 400nm) and modelled DOC is supressed in all three

revegetation catchments by values of up to 10 au m-1 or 17 mg/l and greater respectively.

The data also indicates that at sites R1 l and R2s the suppression effect is greatest after the

first lime and fertiliser application. The sensitivity analysis of the modelled data (Figure 5)

suggests that the estimates of modelled DOC suppression may be an overestimate due to a

shift in the colour to carbon ratio (Figure 5b) during the suppression periods. However the

analysis still shows suppression in excess of 10 mg/l (Figure 5c and d) and values of DOC

suppression measured at site R3s (Figure 5a) are up to 14 mg/l or 50 % less than the

control value of 28 mg/l. At catchments R1l and R2s in 2011 the suppression effect

appeared to last for a similar period to the elevated Ca2+, PO43- and K+ levels (100-200

days). There is also evidence that catchments R1l and R2s showed a similar pattern in 2012

and 2013, but the suppression is less consistent. Lower colour suppression at catchment

R3s was associated with lower peaks in Ca2+, PO43- and K+ (see section 3.1.1).

21

The patterns in DOC concentration and colour do not suggest any net increases in carbon

export. Specifically, this suggests that this method of restoration will not make water

treatment harder or lead to increased CO2 release from the fluvial pathway. However, it is

important to stress that monitoring of these catchments should continue, as re-establishing

vegetation is likely to continue to change the system for at least 10 years post application.

The suppression of DOC and colour in run-off waters following soil liming and

fertilisation, is both a novel and unexpected finding not reported before which merits

further research. Other studies suggest two possible mechanisms which could explain this.

Firstly Ca2+ ions may bind with negatively charged humic material causing it to flocculate

out of solution (Römkens et al., 1996), this could account for both the reductions in water

colour and colour adjusted for DOC concentration. Secondly bacterial sulphate reduction

(BSR) may supress DOC where a labile organic substrate is consumed (Bartlett et al.,

2005). Sulphate stored in high levels in these soils (see section 3.1.2) could be released as

a result of a rise in pH caused by liming as less bonding sites are available for SO42- ions

(Curtin and Syers, 1990). Whilst suppression of labile material is more likely to affect less

coloured DOC, this second mechanism could occur concurrently with the Ca effect.

22

Figure 4: Data for modelled DOC concentration and absorbance at 400nm (Abs400) showing bare peat control catchment C and deviation from catchment C for revegetation catchments R1l, R2s and R3. Vertical lines mark the start of lime and fertiliser applications in a given year and horizontal lines show a 3 point moving average. Time is from day 0 to 1496 ( 01/12/2010 to 05/01/2015).

23

Figure 5: Data for measured DOC and colour carbon ratios and a sensitivity analysis to recalculate modelled DOC based on colour carbon ratio shifts (see section 2.5). a) Deviation of measured DOC at site R3s from catchment C, b) difference between modelled and actual Abs400:DOC ratio. Reduction in colour carbon ratio of 0.23 applied during absorbance suppression period (between horizontal lines) at catchments c) R1 l and d) R2s. Vertical lines in a) and b) and the first line in c) and d) mark the start of lime and fertiliser applications in a given year. The second vertical line in c) and d) marks the end of the period of absorbance suppression. Horizontal lines show a 3 point moving average. Time is from day 0 to 1496 (01/12/2010 to 05/01/2015), but stops at day 400 (05/01/2012) in c) and d).

24

4. Conclusions

Major landscape scale restoration of degraded peatlands is being undertaken in the uplands of

the UK. This involves aerial application of lime and fertiliser to ecosystems which are

important areas of water supply, and of carbon storage and sequestration. This study has for

the first time assessed catchment scale impacts of the restoration process on run-off water

quality and dissolved carbon losses. The findings have implications both for ongoing

practical restoration work and for understanding of the impacts of restoration on peatland

carbon cycling.

In this study peatland revegetation with lime and fertiliser application leads to no

detectable long term change in DOC concentration, over a four year monitoring

period.

However interestingly the treatment produces significant short term suppression (up

to 6 months) of colour, and to a lesser extent DOC concentration in catchment

drainage waters. This is both a novel and unexpected finding which suggests short

term impacts on both the composition and quantity of DOC.

The suppression mechanism merits further investigation and results in reduced DOC

concentration by up to 14 mg/l or 50% of control values, combined with periods of

reduced colour carbon ratios.

The most notable direct effect on water quality is fluvial export of PO43- above

recommended levels in the first year of application; this suggests P application is in

excess of the ecosystem capacity to utilise in the first year of restoration and so the

proportion of P in the first treatment would benefit from further evaluation.

25

Acknowledgements

This work was part funded by United Utilities, the Moors for the Future Partnership and the

National Trust.

Thank you to all the people who helped with fieldwork including Clare Brown, Michael

Pilkington and Tom Spencer and to Donald Edokpa and Nicole Holland for both field and

laboratory work.

Thank you to Jon Yarwood and John Moore at Manchester University Geography

Laboratories for providing technical support.

26

Bibliography

Anderson, P., Radford, E., 1994. Changes in vegetation following reduction in grazing

pressure on the National Trust’s Kinder Estate, Peak District, Derbyshire, England. Biol.

Conserv. 69, 55–63. doi:10.1016/0006-3207(94)90328-X

Andersson, S., Nilsson, S.I., 2001. Influence of pH and temperature on microbial activity,

substrate availability of soil-solution bacteria and leaching of dissolved organic carbon

in a mor humus. Soil Biol. Biochem. 33, 1181–1191. doi:10.1016/S0038-

0717(01)00022-0

Aro, L., Kaunisto, S., Saarinen, M., 1997. Afforestation of peat cutaway areas. Project report

1986–1995. Finnish Forest Research Institute Research Papers 634.

Baligar, V.C., Fageria, N.K., He, Z.L., 2001. Nutrient Use Efficiency in Plants. Commun.

Soil Sci. Plant Anal. 32, 921–950. doi:10.1081/CSS-100104098

Bartlett, R., Bottrell, S., Coulson, J., 2005. Behaviour of sulphur during diagenesis of a

maritime ombrotrophic peat from Yell, Shetland Islands, UK. Appl. Geochemistry 20,

1597–1605. doi:10.1016/j.apgeochem.2005.04.008

Biasi, C., Lind, S.E., Pekkarinen, N.M., Huttunen, J.T., Shurpali, N.J., Hyvönen, N.P., Repo,

M.E., Martikainen, P.J., 2008. Direct experimental evidence for the contribution of lime

to CO2 release from managed peat soil. Soil Biol. Biochem. 40, 2660–2669.

doi:10.1016/j.soilbio.2008.07.011

Bussel, J., Jones, D.L., Healey, J.R., Pullin, A.S., 2010. How do draining and re-wetting

affect carbon stores and greenhous gas fluxes in peatland soils? Collab. Environ. Evid.

Rev. 08-012 44, 73. doi:www.environmentalevidence.org/SR49.html

Caporn, S., Sen, R., Field, C., Jones, E., Carroll, J., Dise, N., Streetmanchester, C., 2007.

Consequences of lime and fertiliser application for moorland restoration and carbon

balance Research report to Moors for the Future 1–29.

Caraco, N.F., Cole, J.J., Likens, G.E., 1989. Evidence for sulphate-controlled phosphorus

release from sediments of aquatic systems. Nature 341, 316–318. doi:10.1038/341316a0

Chapman, S., Buttler, A., Francez, A.-J., Laggoun-Défarge, F., Vasander, H., Schloter, M.,

Combe, J., Grosvernier, P., Harms, H., Epron, D., Gilbert, D., Mitchell, E., 2003.

Exploitation of northern peatlands and biodiversity maintenance: a conflict between

economy and ecology. Front. Ecol. Environ. 1, 525–532. doi:10.2307/3868163

27

Curtin, D., Syers, J.K., 1990. Extractability and adsorption of sulphate in soils. J. Soil Sci. 41,

305–312. doi:10.1111/j.1365-2389.1990.tb00065.x

Daniels, S.M., Agnew, C.T., Allott, T.E.H., Evans, M.G., 2008. Water table variability and

runoff generation in an eroded peatland, South Pennines, UK. J. Hydrol. 361, 214–226.

doi:10.1016/j.jhydrol.2008.07.042

Di, H.J., Cameron, K.C., 2002. Nitrate leaching in temperate agroecosystems: Sources,

factors and mitigating strategies. Nutr. Cycl. Agroecosystems 64, 237–256.

doi:10.1023/A:1021471531188

Evans, M., Warburton, J., 2007. Geomorphology of Upland Peat: Erosion, Form and

Landscape Change. Blackwell, Oxford.

Ferguson, P., Lee, J.A., Bell, J.N.B., 1978. Effects of sulphur pollutants on the growth of

Sphagnum species. Environ. Pollut. 16, 151–162. doi:10.1016/0013-9327(78)90129-5

Finér, L., Laine, J., 1998. Root dynamics at drained peatland sites of different fertility in

southern Finland. Plant Soil 201, 27–36. doi:10.1023/A:1004373822354

González, E., Rochefort, L., 2014. Drivers of success in 53 cutover bogs restored by a moss

layer transfer technique. Ecol. Eng. 68, 279–290. doi:10.1016/j.ecoleng.2014.03.051

Gorham, E., Janssens, J., Wheeler, G., 1987. The natural and anthropogenic acidification of

peatlands, in: Hutchinson, T.C., Meema, K. (Eds.), Effects of Atmospheric Pollutants on

Forests, Wetlands and Agricultural Ecosystems. Springer, New York, pp. 493–512.

Grieve, I.C., 1990a. Soil and soil solution chemical-composition at 3 sites within the Loch

Dee catchment, SW Scotland. J. Soil Sci. 41, 269–277. doi:10.1111/j.1365-

2389.1990.tb00062.x

Grieve, I.C., 1990b. Variations in chemical composition of the soil solution over a four-year

period at an upland site in southwest Scotland. Geoderma 46, 351–362.

doi:10.1016/0016-7061(90)90024-4

Kimmel, K., Mander, U., 2010. Ecosystem services of peatlands: Implications for restoration.

Prog. Phys. Geogr. 34, 491–514. doi:10.1177/0309133310365595

Koehler, A.K., Murphy, K., Kiely, G., Sottocornola, M., 2009. Seasonal variation of DOC

concentration and annual loss of DOC from an Atlantic blanket bog in South Western

Ireland. Biogeochemistry 95, 231–242. doi:10.1007/s10533-009-9333-9

Ledesma, J.L.J., Kohler, S.J., Futter, M.N., 2012. Long-term dynamics of dissolved organic

carbon: Implications for drinking water supply. Sci. Total Environ. 432, 1–11.

doi:10.1016/j.scitotenv.2012.05.071

Limpens, J., Berendse, F., Blodau, C., Canadell, J.G., Freeman, C., Holden, J., Roulet, N.T.,

28

Rydin, H., Schaepman-Strub, G., 2008. Peatlands and the carbon cycle: from local

processes to global implications - a synthesis. Biogeosciences 5, 1475–1491.

doi:10.5194/bgd-5-1379-2008

Lund, M., Christensen, T.R., Mastepanov, M., Lindroth, A., Ström, L., 2009. Effects of N

and P fertilization on the greenhouse gas exchange in two northern peatlands with

contrasting N deposition rates. Biogeosciences 6, 2135–2144. doi:10.5194/bg-6-2135-

2009

McDowell, R.W., Monaghan, R.M., 2014. Extreme Phosphorus Losses in Drainage from

Grazed Dairy Pastures on Marginal Land. J. Environ. Qual. 44, 545–551.

doi:10.2134/jeq2014.04.0160

Mcdowell, R.W., Sharpley, A.N., Condron, L.M., Haygarth, P.M., Brookes, P.C., 2001.

Processes controlling soil phosphorus release to runoff and implications for agricultural

management. Nutr. Cycl. Agroecosystems 59, 269–284. doi:10.1023/A:1014419206761

Miller, M.H., 1978. Contribution of Nitrogen and Phosphorus to Subsurface Drainage Water

from Intensively Cropped Mineral and Organic Soils in Ontario. J. Environ. Qual. 8, 42–

48. doi:10.2134/jeq1979.00472425000800010011x

Page, S., Hosciło, A., Wösten, H., Jauhiainen, J., Silvius, M., Rieley, J., Ritzema, H., Tansey,

K., Graham, L., Vasander, H., Limin, S., 2009. Restoration ecology of lowland tropical

peatlands in Southeast Asia: Current knowledge and future research directions.

Ecosystems 12, 888–905. doi:10.1007/s10021-008-9216-2

Parry, L.E., Holden, J., Chapman, P.J., 2014. Restoration of blanket peatlands. J. Environ.

Manage. 133, 193–205. doi:10.1016/j.jenvman.2013.11.033

Qassim, S.M., Dixon, S.D., Rowson, J.G., Worrall, F., Evans, M.G., Bonn, A., 2014. A 5-

year study of the impact of peatland revegetation upon DOC concentrations. J. Hydrol.

519, 3578–3590. doi:10.1016/j.jhydrol.2014.11.014

Rochefort, L., Lode, E., 2006. Restoration of degraded boreal peatlands. Ecol. Stud. 188,

382–423. doi:10.1007/978-3-540-31913-9

Römkens, P., Bril, J., Salomons, W., 1996. Interaction between Ca 2+ and dissolved organic

carbon: implications for metal mobilization. Appl. Geochemistry 11.

Salonen, V., Laaksonen, M., 1994. Effects of fertilization, liming, watering and tillage on

plant colonization of bare peat surfaces. Ann. Bot. Fenn. 31, 29–36.

Scholz, M., Trepel, M., 2004. Water quality characteristics of vegetated groundwater-fed

ditches in a riparian peatland. Sci. Total Environ. 332, 109–122.

doi:10.1016/j.scitotenv.2004.02.001

29

Sims, J.T., Simard, R.R., Joern, B.C., 1998. Phosphorus Loss in Agricultural Drainage:

Historical Perspective and Current Research. J. Environ. Qual. 27, 277–293.

doi:10.2134/jeq1998.00472425002700020006x

Smith, K.A., Jackson, D.R., Withers, P.J.A., 2001. Nutrient losses by surface run-off

following the application of organic manures to arable land. 2. Phosphorus. Environ.

Pollut. 112, 53–60. doi:10.1016/S0269-7491(00)00098-1

Stimson, A.G., 2016. Fluvial carbon dynamics in degraded peatland catchments. Unpublished

PhD Thesis, University of Manchester.

Tallis, J.H., 1998. Growth and degradation of British and Irish blanket mires. Environ. Rev.

6, 81–122. doi:10.1139/a98-006

Turetsky, M., Wieder, K., Halsey, L., Vitt, D., 2002. Current disturbance and the diminishing

peatland carbon sink 29, 7–10.

Vega, M., Pardo, R., Barrado, E., Debán, L., 1998. Assessment of seasonal and polluting

effects on the quality of river water by exploratory data analysis. Water Res. 32, 3581–

3592. doi:10.1016/S0043-1354(98)00138-9

Wallage, Z.E., Holden, J., Mcdonald, A.T., 2006. Drain blocking : An effective treatment for

reducing dissolved organic carbon loss and water discolouration in a drained peatland

367, 811–821. doi:10.1016/j.scitotenv.2006.02.010

White, P.J., Hammond, J.P., 2006. Updating the estimate of the sources of phosphorus in UK

waters.

Williams, B.L., Young, M., 1985. Nutrient fluxes in runoff on reseeded blanket bog , limed

and fertilized with urea , phosphorus and potassium.

Worrall, F., Burt, T.P., Adamson, J., 2006. The rate of and controls upon DOC loss in a peat

catchment 321, 311–325. doi:10.1016/j.jhydrol.2005.08.019

Wösten, J.H.M., Van Den Berg, J., Van Eijk, P., Gevers, G.J.M., Giesen, W.B.J.T., Hooijer,

A., Idris, A., Leenman, P.H., Rais, D.S., Siderius, C., Silvius, M.J., Suryadiputra, N.,

Wibisono, I.T., 2006. Interrelationships between Hydrology and Ecology in Fire

Degraded Tropical Peat Swamp Forests. Int. J. Water Resour. Dev. 22, 157–174.

doi:10.1080/07900620500405973

Wright, R., Alewell, C., 2001. Trends in nitrogen deposition and leaching in acid-sensitive

streams in Europe. Hydrol. Earth Syst. Sci. Discuss. 5, 229–310. doi:10.5194/hess-5-

299-2001

Yu, Z., Loisel, J., Brosseau, D.P., Beilman, D.W., Hunt, S.J., 2010. Global peatland dynamics

since the Last Glacial Maximum 37, 1–5. doi:10.1029/2010GL043584

30

List of abbreviations

DOC dissolved organic carbon

N nitrogen

P phosphorous

S sulphur

CO2 carbon dioxide

SO2 sulphur dioxide

Ca calcium

K potassium

KCl potassium chloride

(NH4)2 HPO4 di-ammonium phosphate

PO43- phosphate

NO3- nitrate

Ca2+ calcium (ion)

K+ potassium (ion)

SO42- sulphate (ion)

31