Water table depth (2007 – 2011)

Over the five year study monitoring six Bleaklow sites, WTD variation was linked to differences between study sites. Furthermore, seasonal and annual variation was as important as variation between site plots. The factor month was related to seasonality (linked to environmental variables and vegetation). The importance of inter-annual seasonal variation explains the general increasing trend in water table depth over the five year study period. Environmental variables were investigates and it was found that rainfall was linked to WTD, at multiple temporal scales (monthly mean rainfall; and rainfall total at a short time period, 1 - 2 days

123 prior WTD in-field measurement). Temperature was important in influencing WTD at a short temporal scale (1 - 2 days prior field monitoring). Increased rainfall volume was correlated to an in increase in WT. Hence increased rainfall would raise WTD closer to the soil surface. However, temperature was more important on a shorter time interval. Therefore rainfall and temperature events could influence WTD. However, the importance of rainfall was dropped out of the ANCOVA as the variables most important to WTD other than the factor site were the environmental covariates PAR and air temperature (measured during sampling period). The significant difference between bare control sites and the naturally revegetated site indicate that site morphology influences WTD, as neither of the sites received treatment and yet they significantly differ in both WTD and vegetation cover.

Analysis of WTD using dominant plot cover as a factor instead of site, found over the five year period, vegetation cover was important but explained less WTD variation than site could. In term of reduced depth of WT any vegetation cover was preferential to bare soil cover. The low of sensitivity of WTD to rainfall and the importance of site over vegetation cover in explaining WTD variation, support the finding by Allott et al. (2009) there is a distinct temporal-hydrology in Bleaklow blanket peats sites. The intact least disturbed sites such as that at the least distubed vegetated control, had near-surface (<10 cm) WTDs most of the time.

Water table fluctuation according Breeuwer et al. (2009) is an important factor in controlling vegetation type, whereby increased occurrence of periods with deeper water tables may bring about a shift in dominant Sphagnum spp. as well as a shift from grasses to sedge cover, and could induce a shift towards vascular communities, as found by Urbanova et al. (2012). As WTD was deepest at the bare soil control sites (bare gully and bare flat) it is very difficult for pioneer species, especially with short roots to establish and access the water.

124 Furthermore, WTD fluctuation influences total biomass production and thus could impact carbon sequestration and hydrological characteristics of bogs (Breeuwer et al. 2009). The site with the smallest CV was the bare gully site; the bare soil site with the significantly deepest WTD. The sites with the largest CV are associated with greater annual fluctuation, as found at the geojute soil stabilisation, which was the restoration site with lowest bare soil cover dominance. Bare sites on Bleaklow had deeper water table, no vascular species and less WTD fluctuation than other Bleaklow sites. However, as the WTD at bare sites were significantly deeper than the other sites, the WTD fluctuation would have less interaction or impact on vegetation present at the peat surface.

The study indicated that although treatment of sites raised WTD closer to the surface, as a result of change of vegetation, the hydrological regime was difficult to restore. This is because eroded and intact peats have clearly distinct hydrological regimes (Allott et al. 2009), with disturbed and eroded bog having a lower water retention capacity than pristine bogs (Daniels et al. 2008, Rothwell et al. 2009). Results from the sites used in this study suggest that peat surface treatments (i.e. seeding, liming and fertilisation) either have no or only a small impact on WTDs within a relatively short time scale of years. For a decreased depth in WT at a two year time scale, intervention using gully blocking is recommended (depending on site morphology). Additionally stabilisation techniques (are associated with sedge growth, as sedge dominated plots) had the shallowest WTD after two years and across the five year study. Such techniques would be recommended in future bare peat hydrological and ecological restoration projects.

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3.5.4 DOC

3.5.4.1 DOC (2008)

After two years of monitoring, in 2008 there was an indication of site DOC fluctuation (greater CV indicated greater fluctuation). The site with greatest success in reducing bare soil dominance in the first two years of the study, SL.Ge-G, had the largest CV. The lowest CV was at bare control B-G, where no restoration efforts were made and the site remained dominated by bare soil cover. Analysis of variance found that in 2008 monthly variation was more important than site. The addition of mean temperature of the month preceding that of sampling month, was found to be a more important variable in determining DOC concentrations than site. In 2008 peak temperatures were reached in August followed by peak total rainfall volumes in September, and then the peak in soil pore water DOC (191.80 mg C/ L) was in November. The lowest concentrations (between 49.80 and 59.01 mg C/ L) were present during the late winter and early spring (January to April).

Seasonality is an important DOC explanatory variable (Clay et al. 2012). Temperature averages over long periods of time (of month instead of days) are useful in models explaining DOC variation. Some of the DOC species can be produced in a relatively short time scale (e.g. route exudate) and some DOC over relatively longer time scales (related to peat break down). The use of the correct covariates at the correct time scale when developing models for DOC, can allow differences in DOC attributable to site variation to become more apparent. It was found that the temperature of the month preceding sampling month was important in explaining DOC concertation. This lag effect of mean temperature on Bleaklow DOC concentrations can be explained by: a) timing of sampling, as 65.5% of field monitoring and sampling was conducted in the first 2.5 weeks of each month; b) soil pore water DOC data is a measurement of concentration not flux, thus there is a potential lag in DOC production in

126 relation to weather events (in the days prior sampling). Temperature can influence the microbial activity and DOC production (Mitchell et al. 2008, Wallage and Holden 2010), and rainfall events ‘flush out’ and DOC adsorbed onto the peat soil particles (Clark et al. 2007, Worrall et al. 2002). Unfortunately the rainfall data is an accumulative value, therefore detail of individual rainfall events are lost, this is possibly a reason why total monthly rainfall was not a significant factor during multivariate analysis.

The importance of the temperature of the months preceding the sampling month indicted a lag between DOC productions and the system flush. This flush mechanism is discussed by Worrall et al. (2006) as the autumn flush, in which the labile organic matter produced during the summer is flushed out during autumn months due to increased rainfall. In 2008, the DOC concentrations at the treatment sites were not significantly different to either the vegetated control sites or the bare soil controls. Clay et al. (2012) discussed findings indicating the vegetated controls were the only two sites which significantly differed to one another (naturally revegetated soil pore water DOC greater than the vegetated control). The variation in DOC concentrations was greatest during the late summer period in particular at the naturally revegetated site. Although there are observational differences, there was a lack of statistical difference between concentrations of DOC between the bare sites and the treated sites. This is could be due to the treated sites slow establishment of vegetation cover, particularly in the case of the seeded and limed and the heather brash which were dominantly bare. The lack of an active vegetation layer to stimulate a soil microbial community on bare and restoration sites, means there was likely to be little activity driving DOC production (Aguilar and Thibodeaux 2005). Analysis of DOC vegetation in 2008 found that without the use of temperature as a covariate, significant differences between DOC were not apparent. In 2008 the bare control DOC did not differ to the vegetated controls or the sites with treatment. However analysis by vegetation dominance revealed that Sphagnum spp. dominated plots

127 were associated with relatively shallow water table depths and higher soil pore water DOC (as found at the naturally revegetating site) than the bare soil control and treatment sites. Grass and sedge species had significantly lower soil pore water DOC (as found the vegetated control). The plots dominated by bare soil cover and shrub plants did not significantly differ. Note the vegetated control sites had the with the shallowest water table were found to significantly differ.

3.5.4.2 DOC (2007 – 2011)

The Bleaklow study sites exhibited a general decreasing trend in DOC concentrations between 2007 and 2010, and in 2011 there was a significant increase in concentrations. The least disturbed vegetated control however had less fluctuation in DOC concentrations over time. It was found that inter-annual seasonality variation was important, as was the interaction of site with year. Furthermore the variation in DOC between site treatment plots was greater than it was between the treatment sites.

Temperature at several time steps was identified as being significantly relating to soil pore water DOC, which is supported the findings of Heathwaite (1993), in which elevated temperatures can elevate decomposition, thus increase in temperatures can result in increased soil pore water DOC (Worrall and Burt 2004). Bonnett et al. (2006) stated the seasonal effect of temperature on DOC may be explained by increased plant and microbial activity. Temperature of bimonthly mean was found to best explain the soil pore water variation. However, month nested within year remained the most important factor. Although it explained a very small portion of variation, temperature was found to be more important in influencing DOC concentrations on Bleaklow than inter-site variation was. It was revealed that the bare gully control had significantly higher DOC than the bare flat interfluve. The bare gully control site had relatively high DOC concentrations and deep water table depth. At dominantly

128 bare sites it would be expected that oxidative and microbial biological processes drive the production of the DOC (Mcknight et al. 1985). Of the three sites with treatments, two (seeded and limed and the heather brash) did not differ from the vegetated control. They also had lower DOC concentrations than the bare gully, but not bare interfluve site. Seasonal variation in DOC production is associated with microbial communities and root exudation (Mitchell et al. 2008, Wallage and Holden 2010). Despite the reduction in bare cover associated with restoration treatments at sites, the concentration of DOC in soil pore water was not significantly different to the controls. Furthermore no significant difference was found between DOC at the different dominate vegetation types.

As previously mentioned, temperature variation was important in explaining DOC concentrations. The lowest soil pore water DOC concentrations for all sites monitored were observe during winter months. As the target of restoration is to encourage sites revegetation and reduction of bare cove sites; it is important to refer to changes over time and how the changes are relative to the controls. It was found that at the end of the study (2011) DOC was significantly greater than in 2007. Bleaklow soil pore water DOC concentrations significantly dropped in 2010 (the year with lowest rainfall and high summer temperatures), followed by a small increase in 2011 (the year with the highest annual rainfall and low temperatures between summer and winter months). The drop in observed DOC in 2010 could be a result of smaller sample size during the summer; however given that the models accounted for monthly temperature variation, the drop in DOC in 2010 is most likely due to differences between years instead of changes between the sites

Despite the changes in vegetation on Bleaklow, restoration sites displayed little evidence of changes in DOC concentrations. Site pH was lower at sites dominated by bare soil cover; however pH was not a significant covariate in explaining DOC concentrations. This could

129 be explained by changes in DOC production but not DOC mobility. Palmer et al. (2013) found: a) a negative correlation between pH and DOC concentrations; b) buffering of acid deposition (i.e. sulphates) varied depending on soil base components. Upon addition of sulphate, soils with a greater sulphates buffering capacity result in a decrease in DOC concentrations. Blanket bogs such as Bleaklow are less sensitive to sulphate input variation than shallow confined peat according to Clark et al. (2011). This could explain why the use rainfall sulphate concentrations as a covariate within ANCOVA did not improve the model or the ability variate in predict DOC concentrations. Clark et al. (2005) found that drought conditions and shallow water table depth were coupled with increased soil sulphate. These conditions were linked to increased pH and increased ionic strength which suppressed the release of DOC. It is a possibility that the low water table conditions simulated draught conditions resulting in reduced DOC solubility therefore suppression of soil pore water DOC concentration. Soil pore water sulphate concentrations were not investigated, and although pH was not a significant covariate in

explaining DOC concentrations it was it terms of E4/E6. The differences in DOC species were

investigated using the UV-Vis absorbance proxy data (E4/E6).

3.5.5 E4/E6

3.5.5.1 E4/E6 (2008)

The ratio of E4/E6 was used as a general indicator of organic molecules MW. Specifically high

E4/E6 is associated with relatively lower MW (fulvic components), and lower E4/E6 is associated

with relatively higher MW (humic components) (Carlsen et al. 2000). In 2008, E4/E6 variation

was better explained through variation between sites than between months (unlike DOC concentration which were largely determined by seasonality). A correlation between pH and

E4/E6 indicated that increases in pH would result in a decrease in E4/E6 toward the humic range.

130 significant relationship between pH and DOC. The relationship between DOC concentrations

and E4/E6 was not clear between sites. This result can be explained by Chen et al. (1978), who

found that E4/E6 ratios were not concentration dependent, but in fact the ratio were correlated

with acidity and pH ( a measure of hydrogen protons which were related to acidity).

Kukkonen et al. (1992) determined the ratios of E4/E6 humic acids ranged from 5.44 to

5.7 and fulvic acids ranged from a ratio of 8.88 to 9.9. Other values for humic were given as 3.8 to 5.8 and fulvic as 7.6-11.5. Carlsen et al. (2000) gave a ratio of >11 for fulvic components. These values are variable according to sample sources. For example, a high amount of lignin

from decaying plant material would results in a higher molecular weight and lower E4/E6.

Based on the research during analysis of E4/E6, a 6.5 ratio was used as an indication samples

were within a humic range, while anything above a ratio of 7 was considered within the fulvic range.

In 2008, analysis of soil pore water E4/E6 found that the least disturbed vegetated

control had the lowest ratio followed by the bare (gully) control sites. E4/E6 of the heather

brash and gully block samples were greater (more fulvic range) than the bare (gully) controls. Analysis by vegetation functional group indicated that sedge dominated plots had the lowest

E4/E6 ratio. The higher (more fulvic range) E4/E6 at sites with treatment indicated that

differences in DOC compounds could be attributed produced to the recently established

vegetation. However, the lack of vegetation at the bare flat site (also with more fulvic E4/E6)

did not support this rational. Instead the differences found in previously bare restored sites could potentially be changes in DOC production and mobility. The least disturbed vegetated

control exhibited the lowest mean E4/E6 (within a humic range), this is possibly related to the

131 at the bare (flat) control could indicate a the production and mobility of humic compound derived from the decomposition of the deeper layers of the hummified bare eroded peat.

3.5.5.2 E4/E6 (2007 – 2011)

Between year 2007 and 2011, all the sites observed a general decrease in E4/E6 and shift from

a more fulvic to humic range DOC. This finding indicated an effect at locality scale. Analysis of variance found that monthly and inter-annual variation were important factors identified. Site

and water table depth were equally important in determining E4/E6 variation, followed by soils

pore water DOC concentration and pH. Temperature was not related to the speciation of the DOC, although important in its production related to erosion and biological activity (Mcknight et al. 1985). The site with the highest E4/E6 was the seeded and limed site, also the restoration site with greatest bare soil cover dominance. As indicated in 2008, the fulvic DOC production could be due to the relatively newly established vegetation in addition to microbial activity

related to the peat breakdown. The sites with the lowest E4/E6 over the five years was the

vegetated control (sedge dominated), and the two bare soil controls (bare gully and bare flat). The soil pore water humic range in DOC is likely as a result of litter layer and bare peat

breakdown. Furthermore, analysis of E4/E6 by most dominated plot cover revealed that

vegetation cover impacted the ratio. Plots dominated by sedge had significantly lower E4/E6

than both bare and moss dominates sites. Thus across the five years, the geojute site did not significantly differ to the heather brashed site. However, the heather brash site, a vegetation cover most similar to the vegetated control (sedge dominated), showed the greatest rise in

water table to the surface. The significant reduction of E4/E6 over time, significantly lower

periods coincided with the lowest DOC measured in the soil pore water on Bleaklow.

Investigation into the importance of pH on DOC speciation and concertation was conducted through ANOVA. The ANOVA indicated that pH of soil pore water was important in

132

explaining variation of E4/E6, therefore pH was related to DOC speciation but not

concentration. The importance of acid forming S and N species where excluded from the DOC concentration ANCOVA as they were relatively unimportant compared to WTD, temperature,

site and year. The covariates S and N were also unimportant in relation to E4/E6.

That variation in the ratio of E4/E6 followed a similar annual trend to the variation in

pH. Overall Soil pore water pH was lower at bare sites than at the more vegetated site (control and site with soil stabilisation). By the end of the study period in 2011, both the bare gully and bare flat sites had a pH <4; such low pH conditions are sub optimal for soil microbial communities and seed germination (Andrus 1986, Caporn et al. 2007, Smith and Read 1997). The least disturbed vegetated control exhibited a slight decrease in pH over time. This indicates an overall effect at locality scale. Furthermore, on Bleaklow the presence of vegetation and low bare peat cover dominance is associated with a higher pH than bare peat dominated soil. Sites with stabilisation techniques increased pH by (increased by: 0.06 at heather brash site, by 0.33 at geojute sites).

As an effect at locality scale was identified, rainfall acid deposition and pH concentrations were investigated. No direct link was established between rainfall acid species and soil pore water DOC concentrations or speciation using ANCOVA. Soil pore water pH was

an important covariate in explaining E4/E6 variation. At the least disturbed vegetated control

and the sits with stabilisation techniques (heather brash and geojute), soil pore water pH was more similar (20% lower than) rainfall pH at that at the bare beat dominated sites, at which soil pore water pH was 30% lower than the rainfall. This indicates the sites less dominated by bare soil cover were more able to resist reduction in pH. The late summer periods are

associated lagging behind a peak in a seasonal peak in E4/E6. This is likely due to the inputs of