UNIVERSITY OF CALGARY. Spatial variability of soil hydrophysical properties in. Canadian Sphagnum dominated peatlands. Jordanna Branham A THESIS

UNIVERSITY OF CALGARY Spatial variability of soil hydrophysical properties in Canadian Sphagnum dominated peatlands by Jordanna Branham A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF GEOGRAPHY CALGARY, ALBERTA JANUARY, 2013 Jordanna Branham 2013

Abstract Patterned peatlands develop through eco-hydrological feedback loops, resulting in a microtopography of hummocks and hollows. Physical and hydrologic properties were compared between climate zones, peatland types, microform types and depth in relation to elevation and the water table, to determine if the ecologic definition of microforms holds true for their hydrologic properties. Study sites were located near St. Charles-de-Bellechasse, Quebec, and Wandering River, Alberta, and consisted of a bog and fen in each location. Cores were extracted from the field and soil physical properties (bulk density, decomposition, and porosity) and hydrologic properties (saturated and unsaturated hydraulic conductivity, water retention and anisotropy), were measured. Climate may play a potential role in the anisotropy of saturated hydraulic conductivity, while peatland type influences the degree of difference between hummocks and hollows. Saturated hydraulic conductivity is dependent on depth, and supports current model assumptions of higher flow in hollows than in hummocks. Finally, unsaturated hydraulic conductivity is dependent on the physical properties of pore size distribution, inactive to active pore ratio and decomposition status. Implications of the results suggest that model assumptions for saturated K should be based on the presence of macropores or mesopores within the peat matrix, and not bulk density alone. Models that currently use only one hydraulic conductivity value for a peatland apply to only the saturated zone, as microforms significantly impact the unsaturated conditions. ii

Acknowledgements I would like to thank my parents who taught me an appreciation for geography and for convincing me that there is more to life than music. I thank the University of Calgary peat lab: Ellen and Megan for their initial work with the bubbles; and Elena and Melanie for helping me watch water drip. And I gratefully thank Dr. Masaki Hayashi for the use of his pressure plates and Michael Callaghan for teaching me how to use them and answering my endless questions. I would like to thank my closest friend Christie for encouraging me to start this, and my boyfriend Ian for helping me see it through. Finally, I would like to thank Dr. Maria Strack for taking me from my undergraduate project to her assistant and finally to my Masters. Without your support, enthusiasm and dedication it would not have been possible. iii

Table of Contents 1. Introduction... 1 1.1 Motivation... 1 1.2 Current State of the Science... 1 1.2.1 Peatland Microforms... 1 1.2.2 Organic Soil Hydrophysical Properties... 6 1.3 Knowledge Gaps... 9 1.4 Objectives... 10 2. Study Sites... 11 2.1 Quebec... 11 2.2 Alberta... 12 2.3 Climate... 14 3. Methods... 16 3.1 Field... 16 3.1.1 Core Extraction... 16 3.1.2 Piezometers... 17 3.1.3 Hydraulic Conductivity (K)... 19 3.1.4 Survey... 19 3.2 Laboratory... 19 3.2.1 Bulk Density... 19 3.2.2 Decomposition... 19 3.2.3 Unsaturated Hydraulic Conductivity... 20 3.2.4 Saturated Hydraulic Conductivity... 21 3.2.5 Porosity... 23 iv

3.3 Statistical Analysis... 24 4. Results... 25 4.1 Soil Physical Parameters... 25 4.1.1 Bulk Density... 25 4.1.2 Porosity... 28 4.1.3 Decomposition... 28 4.2 Hydrologic Parameters... 30 4.2.1 Saturated Hydraulic Conductivity... 30 4.2.1.1 Laboratory... 30 4.2.1.2 Field... 38 4.2.2 Water Retention and Pore Size Distribution... 39 4.2.2.1 Water Retention Curves... 39 4.2.2.2 Pore Size Distribution... 41 4.2.3 Unsaturated Hydraulic Conductivity... 46 5. Discussion... 52 5.1 Hydraulic Conductivity... 52 5.2 Unsaturated Hydraulic Conductivity... 55 5.3 Limitations of the Study... 57 6. Conclusion... 59 v

List of Tables Table 1.1. Saturated and unsaturated hydraulic conductivity (K) values of peat from available literature.... 8 Table 2.1. The 1971-200 climate normal for St. Charles-de-Bellechasse, Quebec (SC), and Wandering River Alberta (WR). Temperature values are the daily averages for each location (Environment Canada, 2011).... 15 Table 4.1 Bulk density (g cm-3) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 26 Table 4.2. General linear model F test statistic and p value for peat bulk density (g cm-3) and von Post decomposition.... 26 Table 4.3. Porosity mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 28 Table 4.4. The von Post scale of decomposition mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 29 Table 4.5. The vertical KSAT (cm s-1) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 32 Table 4.6. The horizontal KSAT (cm s-1) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 32 Table 4.7. The general linear model F test statistic and p value for vertical saturated hydraulic conductivity (KSAT V; cm s-1), horizontal saturated hydraulic conductivity (KSAT H; cm s-1) and anisotropy of the vertical and horizontal hydraulic conductivity in the peat cores.... 33 Table 4.8. Anisotropy mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 36 Table 4.9. The mean unsaturated K (cm s-1) and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core.... 49 Table 4.10. The GLM F statistic and p values for slope of unsaturated hydraulic conductivity vs. volumetric water content.... 50 vi

List of Figures Figure 1.1. Patterned bog in Hammermosen, Sweden, with linear arrangement of hummocks and hollows (Foster et al., 1988)... 6 Figure 2.1. Study site location of Wandering River, Alberta (left star), and St. Charles-de- Bellechasse, Quebec (right star)... 11 Figure 2.2. From left to right, St. Charles-de-Bellechasse fen (SCF) and St. Charles-de-Bellechasse bog (SCB)... 12 Figure 2.3 From left to right, Wandering River fen (WRF) and Wandering River bog (WRB)... 13 Figure 3.1. Cores cut into blocks from WRF hummocks (left) and WRF hollows (right)... 16 Figure 3.2.Piezometer schematic (left), piezometers inserted into a hummocks and hollow pair at WRB, with a second piezometer inserted for future studies (right)... 17 Figure 3.3 Unsaturated hydraulic conductivity lab permeameter based on Price et al. (2008), The peat core, upper and lower discs sit in a Plexiglas cylinder. Water flows from the upper reservoir through the lower disc and up through the peat core before exiting through the upper disc into the lower reservoir where discharge (Q) is recorded. The upper and lower reservoir are kept 4cmapart, maintaining a constant gradient across the core. Then lowered down in 2cm increments to increase head pressure... 21 Figure 3.4. Schematic of a peat sample encased in wax with sheet metal upper walls, based on the modified cube method by Surridge et al. (2005).... 22 Figure 4.1. Boxplot of peatland site and core depth against the measured core bulk density, where the central line of each box is median bulk density, and letters indicate significant difference. The box is bounded by the 75th and 25th percentiles (upper and lower) and the vertical lines indicate the 90th and 10th percentiles (upper and lower).... 27 Figure 4.2. Boxplot of peatland site and microform, hummocks (H) and hollows (W), against the measured core bulk density, where the central line of each box is median bulk density, and letters indicate significant difference. The box is bounded by the 75th and 25th percentiles (upper and lower) and the vertical lines indicate the 90th and 10th percentiles (upper and lower).... 27 Figure 4.3. Boxplot of peatland site and core depth against the von Post decomposition value. Where the centre horizontal line is the median, the box is bounded by the 75th and 25th percentiles (upper and lower) and the vertical lines indicate the 90th and 10th percentiles (upper and lower). Letters indicate significant difference.... 30 Figure 4.4. Boxplot of vertical and horizontal saturated hydraulic conductivity(k) where A) peatland site and microform type vs. vertical K, B) peatland site and microform type vs. horizontal K, C) peatland type and core depth vs. vertical K and D) peatland type and core depth vs. horizontal K. Median K is the centre line of each box. Box plots are bounded by the 75th and 25th percentiles and the centre line is median K, and letters indicate significant difference.... 34 vii

Figure 4.5. Boxplot of microform type and core depth for vertical (A) and horizontal (B) saturated hydraulic conductivity, where median K saturated is the centre line of the box. The box is bounded by the 75th and 25th quartiles, the lines represent the 90th and 10th percentiles and circles indicate outliers. Letters above the boxes indicate significant difference... 35 Figure 4.6. Anisotropy of peatland site and core depth, where positive values indicate greater horizontal K than vertical, while negative values indicate greater vertical K than horizontal.... 37 Figure 4.7. The saturated hydraulic conductivity with depth from piezometer slug tests in hummock and hollow microforms at Wandering River Bog, where error bars indicate the standard error of the mean.... 38 Figure 4.8. The mean water retention curves from the pressure plate analysis for A) St. Charles bog, B) St. Charles fen, C) Wandering River bog, and D) Wandering River fen.... 40 Figure 4.9. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. A) SCB H top, B) WRB H top, C) SCB H btm, D) WRB H btm.... 42 Figure 4.10. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. E) SCB W top, F) WRB W top, G) SCB W btm, H) WRB W btm.... 43 Figure 4.11. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. I) SCF H top, J) WRF H top, K) SCF H btm, L) WRF H btm.... 44 Figure 4.12. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. M) SCF W top, N) WRF W top, O) SCF W btm, P) WRF W btm.... 45 Figure 4.13. Unsaturated hydraulic conductivity with volumetric water content (VWC) where A) is SCB and WRB hummock top cores, B) SCB and WRB hollow tops, C) SCB and WRB hummock bottoms and D) SCB and WRB hollow bottoms... 47 Figure 4.14. Unsaturated hydraulic conductivity with volumetric water content (VWC) where E) is SCF and WRF hummock top cores, F) SCF and WRF hollow tops, G) SCF and WRF hummock bottoms and H) SCF and WRF hollow bottoms.... 48 Figure 4.15. Slope of the Log K unsaturated vs. VWC against peatland site and microform type, where the boxplot represents the 25th and 75th percentile, and the middle line is the median Slope. The 10th and 90th percentiles are the lower and upper vertical lines, respectively, and letters indicate significant difference.... 50 viii

Figure 4.16. Slope of the Log K unsaturated vs. VWC against peatland site and core depth, where the boxplot represents the 25th and 75th percentile, and the middle line is the median Slope. The 10th and 90th percentiles are the lower and upper vertical lines, respectively and outliers represented by *.... 51 Figure 5.1. Peat cores from left to right, SCB W top, WRF H top, SCF H btm and WRB W btm. Decomposition of the peat increases from left to right, excluding WRB W btm where the upper half of the core is less decomposed than the lower half..... 52 ix

1. Introduction 1.1. Motivation Peatlands are wet ecosystems where net primary productivity exceeds decomposition resulting in the accumulation of organic matter over time (Clymo, 1984). In Canada, peatlands cover approximately 12% of the land surface area (Tarnocai et al., 2005), and are estimated to contribute 12% of the annual global methane emissions (Hansen et al., 1989). Hydrology is well recognised as one of the most important controls on the carbon budget of peatlands (Clymo, 1984; Moore et al., 1998). Through ecological and hydrological feedbacks, peatlands are characterised by a microtopography of high and low microforms in the peat surface (Baird et al., 2009). Microforms range from 10 0 to 10 1 m in length while peatlands range from 10 2 to 10 4 m (Baird et al., 2009). Models indicate that these microforms play an important role in the large scale hydrological and biogeochemical function of a peatland (Baird et al., 2009; Belyea and Baird, 2006). Small scale variations in the microform vegetation, peat properties, and carbon biogeochemistry, combined with the water table may compound together and lead to overall ecosystem function. Despite this apparent importance of microforms, few data exist on the difference in physical and hydrological properties between them (Belyea and Baird, 2006). 1.2. Current State of the Science 1.2.1. Peatland Microforms Peatlands and microforms differ in scale by several orders of magnitude. Identifying different microforms within a peatland is based on a change in topography and an ecological difference in the surface species. The microforms consist of topographic highs called hummocks, and topographic lows called hollows (Clymo, 1984). The microtopography varies across the range of peatlands and may have a height difference of over 100cm (Clymo, 1984). The peatlands studied in this thesis have a 1

topographic height difference of 10-20cm between the hummocks and hollows. Hummocks are characterized by tightly packed moss species and the presence of vascular species (often woody shrubs), while hollows are characterized by less compact moss species (Clymo, 1984). These differences in the compaction or ability of mosses to pack into an area may impact both the hydrological and biogeochemical functions within the microforms (Titus and Wagner, 1984). The denser moss species may maintain higher capillary rise and thus a better supply of water for evaporation. However, they also allow greater water retention and therefore greater retention of nutrients, which may result in greater moss growth in hummocks (Titus and Wagner, 1984). Hollow moss species are looser, and dry out more easily when at the same pressure as a hummock (Titus and Wagner, 1984). With less capillary rise, the dryer conditions limit Sphagnum photosynthesis rates, resulting in less moss growth in hollows during drought (Titus and Wagner, 1984). Peatlands are predominantly submerged organic soils that consist of a saturated layer of peat, and a small fraction of unsaturated peat at the surface layer (Clymo, 1984; Ingram, 1978). Typically, the water table is located within 0-50cm of the surface, with up to several metres of submerged peat below (Ingram, 1978; Price et al., 2003). As the moss continues to grow in the unsaturated layer, the underlying moss decomposes and losses structural integrity. As a result, the structures collapse, decreasing pore size, and through capillary action, bring the water table higher (Clymo, 1984; Ingram 1978). This allows surface mosses to maintain contact with the water table, furthering new growth. Due to their larger size, hummocks are further removed from the water table with a larger unsaturated zone, and are more susceptible to aerobic decomposition (Belyea, 2009; Ingram, 1978). Hollows are located much closer to the water table, and have a smaller unsaturated zone, limiting aerobic decomposition. The greater decomposition at hummocks alters the physical structure of the moss, decreasing pore sizes, and releasing nutrients that may be used in new growth (Ingram, 1978). 2

The controls on peatland microform development, initiation, transition and degradation may be divided into two main groups, allogenic and autogenic (Bauer et al., 2003). Allogenic controls are considered external to the ecosystem, and are composed of abiotic factors contributing to peatland development. The strongest control is that of the water table level, where micro-organisms, such as testate amoebae, are used as a proxy to determine the approximate water table location within a peat core (McMullen et al., 2004). Testate amoebae occur on a wet-dry gradient, where specific species exist only during times of specific water availability (Lamentowicz et al., 2008). Through comparison with current known species and water table levels, testate amoebae act as an indicator for past water table levels (Lamentowicz et al., 2008). Microforms may develop and persist under stable water table conditions; however, if the water table becomes too variable, then microforms will cease to remain stationary in both time and space, resulting in a transition or degradation of the formations (McMullen et al., 2004). A variable water table may also help promote the development of microforms; however persistence is dependent upon the relative stability of the water table beneath the individual microforms. The topography of the base of the peatland may also play a role in the development and initiation of microforms (Bauer et al., 2003). A highly variable topography is likely to promote a variable water table within the peatland, until the peat depth is great enough to mitigate this influence (Bauer et al., 2003). The chemistry of the groundwater may also affect microform development and persistence. Groundwater that may be flowing through the subsurface of a peatland may bring in valuable nutrients to the vegetation. The flow pattern of the groundwater may lead to the deposition and availability of nutrients to only certain regions of the peatland, promoting increased growth and the development of microforms (Smart et al., 1989). If the flow pattern changes its course, then the availability of the nutrients would decrease, causing the microforms to degrade or transform into a different structure (Smart et al., 1989). Another allogenic control is that of climate, where high or low 3

humidity levels may promote or retard vegetative growth, helping or hindering the development, persistence or degradation of microforms (Hughes and Barber, 2003). Autogenic controls are defined as internal to the peatland system and consist of biotic factors. These controls are not as strong as the external forcing of the water table; however they do play an important role regarding the internal dynamic of the peatland ecosystem. Once again the water chemistry may affect microform persistence, however in this case it is due to the exudates of the vegetation, as opposed to incoming ground water (Smart et al., 1989). The vegetation may significantly alter the surrounding water chemistry to a level where species competition is limited, and persistence of a microform may occur (Smart et al., 1989). Nutrient flows and transpiration rates are dependent on the vegetation composition. Microforms with a thicker unsaturated layer will have greater nutrient flow due to aerobic decomposition, with evapotranspiration pulling the released nutrients up through the peat column (Eppinga et al., 2008). Vascular species increase transpiration rates in hummocks through root penetration of the unsaturated moss layer to the saturated moss layer (Rietkerk et al., 2004). The increased transpiration allows for greater nutrient flow into the surrounding area of the penetrating roots and thus greater vegetation productivity and peat accumulation. The composition of the species within the peatland affects the ability of the microforms to withstand water table variability (McMullen et al., 2004). Through identification of macrofossils and historical ecology (pollen and persistent organic material), the historical species composition may be estimated (Bauer et al., 2003; McMullen et al., 2004; Smart et al., 1986). The presence of the same or similar species from the surface down through the depth of a peat core suggests that the vegetation composition has not varied greatly through time and that the microforms resisted alteration (Smart et al., 1986). Different growth rates of individual species and their proximity to the fringe of a microform may affect the persistence of the microform (McMullen et al., 2004). Hollows are dominated by species that tend to have more rapid growth rates than hummocks, resulting in the expansion of the 4

hollow at the expense of the hummock (McMullen et al., 2004). When the water table drops, hollow species will dry out and form a crust to prevent continual transpiration losses, while hummock species will continue to transpire at their same lower rate (Belyea, 2009). This causes a constant nutrient flow through the hummocks, allowing for continued growth, accumulation of biomass and eventually peat (Foster and Fritz, 1987). Vegetation that is closer to the middle of the peatland tend to have more stable water tables, allowing for microform persistence, whereas vegetation closer to the edge of the peatland tend to have a more variable water table, decreasing microform persistence (Bauer et al., 2003; Smart et al., 1986). Water flow, when combined with the composition of species within a peatland may lead to the formation of patterning through hummocks (ridges) and hollows (pools) (Fig. 1). It is hypothesized that the denser hummocks allow for a slower water flow through their peat soil, leading to the formation of wetter areas or pools behind them. The hollow peat becomes submerged under the water, and slowly decomposes with no potential for biomass accumulation as the living layer has become isolated from the atmosphere and drowned (Baird et al., 2009; Foster and Fritz, 1987). With only the hummocks open to the atmosphere, they continue to accumulate biomass, becoming larger more dominant landforms (Baird et al., 2009). 5

Figure 1.1. Patterned bog in Hammermosen, Sweden, with linear arrangement of hummocks and hollows (Foster et al., 1988). 1.2.2. Organic Soil Hydrophysical Properties The physical structure of the peat is shaped by peatland formation and biomass accumulation. The unsaturated layer has larger pores, and the potential to store more water than the more compact saturated layer which has smaller pores but a greater capacity to retain water. As the peatland develops, surface moss in the unsaturated layer becomes compacted due to aerobic decomposition and the overburden of the new moss growth (Belyea, 2009; Eppinga et al., 2008). The now compacted moss enters the saturated zone as the smaller pores pull the water table up through capillary flow (Clymo, 1984; Ingram 1978, Price et al., 2003). Peat hydrophysical properties are sharply contrasted between the saturated and unsaturated layers (Charman, 2002). 6

The unsaturated layer is most often lower in bulk density (mass of dry solids / total volume) than the saturated layer, with typical values for unsaturated zone bulk density <0.07g/cm 3, and >0.1g/cm 3 for saturated zone bulk density (Van Seters and Price, 2002). Peat soils are organic soils that consist of two types of pores: 1) active pores that allow for water flow through the peat column, and 2) inactive pores which are the remains of the plant cells acting as dead-ends that limit water flow (Hayward and Clymo, 1982; Hoag and Price, 2007). The porosity over the total peat column of saturated and unsaturated layers is typically around 90%, with the unsaturated layer slightly higher, and saturated layer slightly lower (Dingman, 2002; Rycroft et al., 1975). Volumetric water content in the unsaturated zone can increase and decrease rapidly during times of precipitation and water table fluctuation due to the larger pore size of the moss structure (Charman, 2002). The saturated zone tends to retain its volumetric water content longer, however it takes longer to increase or decrease due to the smaller porosity (Charman, 2002). The hydraulic conductivity (K) is the rate at which water flows through a porous medium, in this case peat (Dingman, 2002). Due to the different physical properties of the saturated and unsaturated layers, the hydraulic conductivity through the peat column is not constant. Smaller pores lead to restricted flow, retarding the rate of flow through the saturated layer, whereas larger pores in the unsaturated layer enable faster flow rates (Charman, 2002). Hydraulic conductivity decreases with depth, as pores decrease in size (Rycroft et al., 1975). Saturated hydraulic conductivity has been widely measured across peatlands, with flow rates recorded that were different by several orders of magnitude (Table 1). The saturated hydraulic conductivity is found to decrease with depth, with saturation starting near 50cm below the surface (Price et al., 2003; Whittington et al., 2007). 7

Table 1.1. Saturated and unsaturated hydraulic conductivity (K) values of peat from available literature. Author Saturated K (cm/s) Unsaturated K (cm/s) Peat Type Boelter, 1965 10-2 to 10-6 Sphagnum spp. Carey et al., 2007 10-4 to 10-6 Sphagnum spp. Mathur and Levesque, 1985 10-2 to 10-3 Brown moss spp. Price et al., 2008 10-1 to 10-2 10-3 to 10-6 Woody, Sphagnum spp. Price and Whittington, 2010 10-2 to 10-6 Sphagnum spp. Rycroft et al., 1975 10-2 to 10-6 Sphagnum spp. Surridge et al., 2005 10-3 to 10-5 Sphagnum spp. Whittington, 2005 10-1 to 10-5 Sphagnum spp. When the surface moss becomes more saturated, the structure may swell and expand, enlarging pore sizes and allowing for more rapid flow through the unsaturated zone (Whittington et al., 2007). Drying out of the surface mosses, or a decrease in the water table causes the moss structure to collapse and squish the pores, retarding flow (Whittington et al., 2007). As such, the fluctuation of the water table, coupled with precipitation events may lead to the vertical movement of the peat column and possibly changes in soil properties (Whittington et al., 2007). A drainage experiment in a Sphagnum dominated peatland determined that hydraulic conductivity decrease following drainage and that this decrease was greatest at hollows where the most peat compression occurred (Whittington et al., 2006). A method for measuring unsaturated hydraulic conductivity in peat has only recently been developed (Holden et al., 2001; Price et al., 2008). Application of the new methods have been limited and non-sphagnum dominated peat has not been well examined (Table 1) (Price et al., 2008). When the unsaturated layer becomes saturated during periods of elevated water tables, the newly saturated near surface layer has been found to be a significant pathway for water flow (Holden et al., 2001). 8

1.3. Knowledge Gaps The soil hydrophysical properties of bulk density, volumetric water content, porosity and hydraulic conductivity have been measured for peat as a whole, with no differentiation between microform types. In Swanson and Grigal s (1988) model, hydraulic conductivity was based on microform type, with one value applied to the microform, regardless of differences in saturated and unsaturated flow. Other models apply only one value of hydraulic conductivity to the entire peatland, assuming difference between microforms and depths are not significant (Rietkerk et al., 2004). Microform hydraulic conductivity in saturated and unsaturated layers and beneath hummocks and hollows has not been quantified (Belyea and Baird, 2006). Differences in the spatial distribution of hydrologic properties across a peatland may result in very different patterns of moisture and water table level, with potential feedback to whole ecosystem hydrology, ecology and biogeochemistry (Baird et al., 2009). Moreover, depending on the persistence of these microforms, differences may be persistent with depth, creating three dimensional patterns of hydrologic variability with implications for peatland hydrologic models (Belyea and Baird, 2006). However, if the hydrologic parameters are not variable, then a simple homogeneous parameter could be appropriate and simplify modelling efforts. 9

1.4. Objectives The arbitrary definition of microform distinction is based on an ecological difference in the surface species and a change in topography. The overall objective of this study is to determine if the arbitrary definition holds true for hydrologic parameters. Specifically, the objectives of the study are to determine: i) the effect of microform type on the main physical parameters of peat (pore size distribution, saturated volumetric water content, and bulk density), ii) iii) the effect of the physical parameters on hydraulic conductivity of hummocks and hollows and, the distribution of hydraulic properties with depth, between peatland types and between climatic regions. The implications of this analysis will be considered through a multi-scalar perspective, from individual microforms to regional peat and climate types. 10

2. Study Sites Peatlands can be further classified by their water inputs, fens receive both precipitation and ground water flows whereas bogs receive only precipitation (Glaser and Janssens, 1986). The study sites consist of a Sphagnum moss dominated fen and bog near Saint-Charles-de-Bellechasse, Quebec and a Sphagnum moss dominated fen and bog near Wandering River, Alberta (Fig. 2.1.). The sites were chosen specifically for the similarity in their ecology, and the dominant presence of Sphagnum moss. Figure 2.1. Study site location of Wandering River, Alberta (left star), and St. Charles-de-Bellechasse, Quebec (right star). 2.1. Quebec Saint-Charles-de-Bellechasse fen (SCF) is a Sphagnum dominated poor fen (46 40 N, 71 10 W) (Fig. 2.2.). A poor fen is nutrient limited, and has a low ph however the conditions are not as extreme as a bog which tends to have very limited nutrient availability, and are the most acidic type of 11

peatland (Charman, 2002). The hummocks are characterized by Sphagnum rubellum, the ericaceous shrub Chamaedaphne calyculata, and sedge Carex oligosperma. Hollows are predominantly Sphagnum cuspidatum, and the sedges Rhynchospora alba and Scirpus subterminalis. The hummock water table was located 10cm below surface whereas it was located 5cm below the hollow surface. Saint-Charles-de-Bellechasse bog (SCB) is a Sphagnum dominated bog with open water pools and shrubby ridges (46 40 N, 71 10 W) (Fig. 2.2.). The hummocks are also Sphagnum rubellum, but include the ericaceous shrubs Chamaedaphne calyculata, Rhododendron groenlandicum, and Kalmia angustifolia. The hollow moss species are Sphagnum cuspidatum and Sphagnum magellanicum, with the ericaceous Vaccinium oxycoccus (cranberry), and sedge Rhynchospora alba. The hummock water table was located 20cm below surface, while the hollow water table was located 5 cm below surface. Figure 2.2. From left to right, St. Charles-de-Bellechasse fen (SCF) and St. Charles-de-Bellechasse bog (SCB). 2.2. Alberta Wandering River fen (WRF) is similar to SCF in that it is also a Sphagnum dominated poor fen (55 54 N, 112 33 W) (Fig. 2.3.). Dwarf black spruce and tamarack (Picea mariana, Larix laricina) are found on the hummocks along with the moss Sphagnum fuscum. Hollows are predominantly 12

Sphagnum magellanicum and Sphagnum angustifolium with the sedge Carex limosa. The hummock water table was 15 cm below surface and the hollow water table was located at the surface, 0 cm. Finally, Wandering River bog (WRB) is a Sphagnum dominated continental bog (55 59 N, 111 82 W) (Fig. 2.3.). Hummocks are Sphagnum fuscum, with shrubs Vaccinium oxycoccus (bog cranberry) and Rhododendron groenlandicum. Hollows are Sphagnum angustifolium and the herb Rubus chamaemorus (cloudberry). The water table was deepest at this site at 40 cm below the hummocks and 30 cm below the hollows. Figure 2.3. From left to right, Wandering River fen (WRF) and Wandering River bog (WRB). 13

2.3. Climate Variations in climate may act as a potential control on soil hydrophysical properties. The SCF and SCB sites are located in a warmer, more coastal climatic region than the continental WRF and WRB sites (Table 2.1.). The consistent Sphagnum ecology of the peatlands enables a comparison of the sites from the local hydrologic to climatic scales. 14

Table 2.1. The 1971-2000 climate normal for St. Charles-de-Bellechasse, Quebec (SC) and Wandering River, Alberta (WR). Temperature values are the daily averages for each location (Environment Canada, 2011). Normal Site Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Temperature SC -12.8-11.1-4.6 3.3 11.2 16.5 19.2 17.9 12.5 6.2-0.7-9.1 -- ( C) WR -14.9-10.7-4.4 4.2 10.6 14.2 16.2 15.2 9.8 4.1-6.2-12.9 -- Precipitation SC 89.9 70.6 90.3 81.2 106.1 114.2 127.8 116.7 125.5 101.7 102.0 104.4 1230.4 (mm) WR 24.9 18.6 17.7 25.5 47.3 91.7 104.5 62.6 42.8 21.5 21.1 25.2 503.4 Note: SC data are from the Quebec Jean Lesage Airport weather station, and WR data are from the Athabasca 2 weather station. 15

3. Methods 3.1. Field 3.1.1. Core Extraction Columns of peat (15x15cm) were cut to a depth of at least 20 cm below the water table, at three hummock and hollow pairs per site (Fig. 3.1.). The columns were frozen to limit tearing and deformation of the vegetation structure when cut and prevent alteration of soil structure due to decomposition. The core extraction process is very damaging to the peat structure; more material is removed than necessary before being frozen. Freezing of the vegetation is considered a negligible source of error as the peat freezes every winter; sub-sampling is done shortly before measurement of hydraulic conductivity commences to limit potential freezer burn. Three sub-samples (7 cm diameter x 5 cm deep) were taken from each column, unsaturated layer (top, 3-8 cm), saturated layer (bottom, 20 cm below the water table), and a uniform depth, independent of water table depth (23-28 cm). The independent depth was isolated to Appendix A to ensure clarity in the observable trends within the results. The SCF and SCB cores were extracted in August 2007, WRF in September 2008, and WRB in August 2011. Figure 3.1. Cores cut into blocks from WRF hummocks (left) and WRF hollows (right). 16

3.1.2. Piezometers Piezometers were made of polyvinylchloride (PVC) pipes. The intake was located 5cm from the bottom of the pipe and was 20cm long, with an even and uniform distribution of ½ holes (Fig. 6). To prevent peat from entering the piezometer, 25 micron Nitex mesh was secured over the intake. The piezometers, with an internal radius of 5.08 cm, and external radius of 6.03 cm, were inserted to -50cm, -75cm, -100cm, -125cm and -150cm. A single insertion point was used as there was no significant difference found between multiple insertion points and a single insertion point for head recovery in peat (Surridge et al., 2005). The single insertion point allowed for measurement of a continuous profile with depth of in situ saturated hydraulic conductivity for each individual microform. Piezometers were installed at three hummock and hollow pairs in WRB (Fig. 3.2.). 175cm 20cm Figure 3.2. Piezometer schematic (left), piezometers inserted into a hummock and hollow pair at WRB, with a second piezometer inserted for future studies (right). 17

3.1.3. Hydraulic Conductivity (K) Saturated hydraulic conductivity (K) was calculated at each of the piezometer depths using the slug test method (Surridge et al. 2005). In order to limit smearing on the intake slot without plugging surrounding pore spaces and altering local hydraulic conductivity, an initial slug of water was inserted into the equilibrated piezometer (Surridge et al. 2005). Slug tests were used to determine K for each piezometer depth as it was easier to complete than a bail test in the field. Surridge et al. (2005) found no significant difference between the bail test and the slug test and that both follow Hvorslev s plot well. The slug tests were performed at WRB in early Aug 2011, using a 600 ml slug which was equivalent to a 30 cm change in head. The rate of head recovery was recorded until a minimum of 90% recovery had been achieved, and each depth was measured 1-2 times depending on the rate at which recovery occurred. Additional replicates were not considered necessary as the water table does not significantly fluctuate over the course of the growing season (Kellner and Halldin, 2002). Water table fluctuations occur after rain events however these are spontaneous events producing fluctuations from the normal value (Whittington, 2005). Values for K were calculated as outlined in Freeze and Cherry (1979), based on Hvorslev (1951): ( ) Equation 3.1 where r and R are the internal and external radii of the piezometer (cm), L is the length of the slotted intake (cm), and T 0 is the lag time parameter (s) calculated from the head recovery curve of the slug test. 18

3.1.4.Survey Vegetation surveys were completed at all four sites, identifying the dominant moss species per microform type and any other characteristic vegetation. A site line was also installed at WRB to establish the difference in hummock and hollow height from both surface elevation and water table depth. 3.2. Laboratory 3.2.1. Bulk Density The standard method outlined by Freeze and Cherry (1979) was used to determine the bulk density, dry mass per volume, for each peat core Equation 3.2 where ρ b is bulk density (g cm.1 ), M S is the dried mass of the soil (g), and V T is the total volume (cm 3 )of the peat core. This method was the last one used on the peat cores as it is highly destructive and alters the physical properties of the peat matrix. 3.2.2. Decomposition The state of peat decomposition was determined using the von Post scale of decomposition (Soil Classification Working Group, 1998). This is a scale of 1 10, where 1 is no decomposition and 10 is fully decomposed. It requires the observer to make qualitative statements on the state of decomposition from a standard set of guidelines. 19

3.2.3. Unsaturated Hydraulic Conductivity A lab permeameter was used to determine the vertical unsaturated hydraulic conductivity at decreasing moisture contents of the sub-sampled peat cores (Price et al., 2008). The sample was submerged in distilled water for 12 hours to achieve full saturation before being placed on a 0.25 micron Nitex disc, with an acrylic cylinder encasing the core, and a second upper 0.25 micron Nitex disc placed on top of the core. Water flows from the upper reservoir through the lower disc and out through the upper disc into the lower reservoir (Fig. 3.3.). As the peat is under tension and unsaturated, the acrylic cylinder does not need to make a tight seal around the peat core. The reservoirs remain 4 cm apart, applying a constant gradient to the core, and were moved downward in 2 cm increments, increasing the tension on the core and decreasing moisture content. Tension on the core started at -2cm (where tension is measured relative to the centre of the 5 cm core height) and increased to a maximum of -20cm. Rate of discharge through the core was recorded from the lower reservoir, and then converted into K using Darcy s law: Equation 3.3 where Q is discharge (cm s -1 ), A is area of the core (cm 2 ), is change in head over the core, and is the length of the core (Freeze and Cherry, 1979). Unsaturated flow is predominantly driven by gravity drainage, therefore horizontal unsaturated K will not be measured as flow is assumed to be negligible in this direction. 20

Figure 3.3. Unsaturated hydraulic conductivity lab permeameter based on Price et al. (2008). The peat core, upper and lower discs sit in a Plexiglas cylinder. Water flows from the upper reservoir through the lower disc and up through the peat core before exiting through the upper disc into the lower reservoir where discharge (Q) is recorded. The upper and lower reservoirs are kept 4cm apart, maintaining a constant gradient across the core. Then lowered down in 2cm increments to decrease the head pressure. 3.2.4. Saturated Hydraulic Conductivity The use of a mineral soil method for peat saturated K cannot be applied as the peat core does not form a strong enough seal with the walls of the mineral soil permeameter resulting in preferential flow around the core. A peat saturated K method has been developed by Surridge et al. (2005), based on the modified cube method described by Beckwith et al. (2003). The core is first encased in a thin layer of wax, before the sheet metal walls are applied to the top of the core. The walls are then secured with wax, and allowed to cool and set (Fig. 3.4). Using a thin sharp knife, the wax was cut and peeled 21

from the peat core on the opposing side to the metal walls, and within the metal walls. A constant head was then applied across the core, and rate of discharge recorded. Darcy s law (Equation 3.3) was used to determine the saturated hydraulic conductivity of the core. This method was applied to both the vertical and horizontal axis of the peat cores to determine if there is anisotropy in saturated K. Anisotropy was calculated as Equation 3.4 where Ksat H is the horizontal saturated K and Ksat V is the vertical saturated K (Beckwith et al., 2003; Surridge et al., 2005). Positive anisotropy values indicate greater horizontal K than vertical, while negative values indicate greater vertical K than horizontal. Figure 3.4. Schematic of a peat sample encased in wax with sheet metal upper walls, based on the modified cube method by Surridge et al. (2005). 22

3.2.5. Porosity Total porosity is assumed to be equal to the saturated water content of the peat matrix (Boelter 1969). Total porosity was obtained by subtracting the dry mass per volume from the saturated mass per volume of the peat. Equation 3.5 Where ρ b bulk density (g cm -3 ) and ρ s is particle density (g cm -3 ). Particle density was determined to be 1.47 g cm -3, based on average literature values from Petrone et al., (2008) and Brandyk et al., (2003). Water retention curves for each core were obtained through the standard pressure plate extractor method (Carey et al., 2007). Cores were submerged for 12 hours before being placed in the extractor. Volume and mass of each core were then recorded at increasing pressures (10 mbar, 25 mbar, 50 mbar, 100 mbar, 200 mbar, and 300 mbar). The theoretical pore size distribution for each core was determined on the basis of a given pressure head using the capillary rise equation (Bear, 1972) Equation 3.6 where r is pore radius (mm), γ is the surface tension of water (72.8 g s -2 ), β is the contact angle ( 40 for moderately hydrophobic organic soils (Carey et al., 2007), ρ is the density of water (g mm -1 ), g is gravitational acceleration (mm s -2 ) and h is pressure head (mm). 23

3.3. Statistical Analysis Using Minitab 14 descriptive statistics were calculated for all data sets before normality tests were conducted. If data were not normal, a log transformation was applied before further statistical analyses were completed. A general linear model (GLM) was used to determine the correlation between the measured variables and parameters of climate (SC or WR), peatland type (bog or fen), microform (hummock or hollow) and depth of core (top or bottom). In the GLM, the parameters were compared individually and as six 2-way interactions, four 3-way interactions and one 4-way interaction as degrees of freedom were large enough to permit for all comparisons. Pearson s correlation was also run between the physical and hydrological properties to evaluate regressions. 24

4. Results The results of this thesis are divided into two main sections, Soil Physical Parameters and Hydrological Parameters. This is to facilitate maintaining focus on the development of a specific theme or set of processes. The Discussion chapter will integrate all of the Results sections. 4. 1. Soil Physical Parameters 4.1.1. Bulk Density Bulk density was found to vary significantly between climate, peatland types, microforms and depth, with also several significant interactions (Table 4.1, Table 4.2). In the climate-microform interaction, the SC hummocks were found to be significantly more dense than the SC hollows. No difference was found in the WR hummocks or hollows. The most noticeable difference was found in the interaction between sample site (peatland, separated by climate) and core depth (Fig. 4.1).The bottom (btm) cores were significantly more dense than the top cores, with a more pronounced trend in bogs than fens (One-way nova, df: 47, F: 5.52, p: 0.000). Microforms were also significantly different from one another, however the trends were not as clear (One-way Anova, df: 47, F: 3.87, p: 0.003). In the SC climate, hummocks were significantly more dense than hollows at the fen, with a similar trend noted in the bog (Fig. 4.2). In the WR climate, there was no significant difference between hummocks and hollows (Fig. 4.2). 25

Table 4.1. Bulk density (g cm -3 ) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 0.032 0.0035 btm 0.081 0.011 top 0.030 0.0073 btm 0.060 0.0065 top 0.076 0.045 btm 0.085 0.024 top 0.020 0.0049 btm 0.033 0.0055 top 0.028 0.0021 btm 0.11 0.055 top 0.064 0.026 btm 0.12 0.025 top 0.037 0.0046 btm 0.059 0.0049 top 0.046 0.0041 btm 0.053 0.0043 Table 4.2. General linear model F test statistic and p value for peat bulk density (g cm -3 ) and von Post decomposition. Parameter Bulk Density von Post F p F p Climate 9.00 0.005 14.38 0.001 Peatland 6.41 0.016 24.60 0.000 Microform 5.23 0.029 14.38 0.001 Depth 61.33 0.000 230.13 0.000 Climate x Peatland 2.88 0.10 0.090 0.77 Climate x Microform 32.35 0.000 53.19 0.000 Climate x Depth 0.080 0.78 0.00 1.00 Peatland x Microform 18.05 0.000 0.090 0.77 Peatland x Depth 12.56 0.001 27.57 0.000 Microform x Depth 1.70 0.20 1.36 0.25 Climate x Peatland x Microform 2.32 0.14 2.13 0.15 Climate x Peatland x Depth 0.49 0.49 8.51 0.006 Climate x Microform x Depth 2.48 0.13 0.34 0.56 Peatland x Microform x Depth 1.68 0.21 1.36 0.25 Climate x Peatland x Microform x Depth 0.18 0.67 0.34 0.56 26

Bulk Density (g cm -3 ) Bulk Density (g cm -3 ) 0.18 0.16 a 0.14 0.12 abc bc 0.10 ab c 0.08 0.06 0.04 c ac c 0.02 0.00 Depth Site btm top SCB btm top SCF btm top WRB btm top WRF Figure 4.1. Boxplot of peatland site and core depth against the measured core bulk density, where the central line of each box is median bulk density, and letters indicate significant difference. The box is bounded by the 75 th and 25 th percentiles (upper and lower) and the vertical lines indicate the 90 th and 10 th percentiles (upper and lower). 0.18 0.16 ab a 0.14 0.12 a 0.10 ab 0.08 0.06 0.04 ab b ab ab 0.02 0.00 M/F Site H W SCB H SCF W H W WRB H W WRF Figure 4.2. Boxplot of peatland site and microform, hummocks (H) and hollows (W), against the measured core bulk density, where the central line of each box is median bulk density, and letters indicate significant difference. The box is bounded by the 75 th and 25 th percentiles (upper and lower) and the vertical lines indicate the 90 th and 10 th percentiles (upper and lower). 27

4.1.2. Porosity Mean porosity was higher in the top cores, with greater differences between top and bottom cores in the bogs than fens (Table 4.3). Porosity was calculated using a mean literature value for particle density. As particle density was not measured for each sample, the resulting calculated porosity distribution was the inverse of the bulk density distribution and not included to limit repetition. Table 4.3. Porosity mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 0.98 0.0024 btm 0.95 0.0073 top 0.98 0.0050 btm 0.96 0.0044 top 0.95 0.030 btm 0.94 0.016 top 0.97 0.0033 btm 0.98 0.0038 top 0.98 0.0014 btm 0.93 0.038 top 0.96 0.018 btm 0.92 0.017 top 0.97 0.0031 btm 0.96 0.0033 top 0.97 0.0028 btm 0.96 0.0029 4.1.3. Decomposition Peat decomposition was significantly different between climate, peatland type, microforms and depth (Table 4.2, Table 4.4). In the climate-microform interaction SC hollows were the most decomposed, whereas SC hummocks, WR hollows and WR hummocks were significantly less 28

decomposed but not different from one another (Table 4.2). The most notable trend in decomposition was observed in the peatland-depth interaction where greater decomposition was observed in all bottom cores (One-way ANOVA, df: 47, F: 16.58, p: 0.000) (Fig. 4.3). The bogs display a greater difference between the top and bottom cores than the fens (Fig. 4.3). The three-way interaction of climatepeatland-depth was significant, however due to the complexity of the interaction, cannot be easily interpreted. Table 4.4. The von Post scale of decomposition mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 2.33 0.58 btm 5.17 0.29 top 1.33 0.58 btm 3.50 0.50 top 2.50 0.87 btm 4.17 0.29 top 0.50 0.00 btm 2.50 0.50 top 1.67 0.58 btm 5.33 0.58 top 2.33 0.58 btm 5.33 0.58 top 2.00 0.00 btm 3.17 0.29 top 2.83 0.29 btm 3.67 0.58 29

Von Post 6 ac c 5 4 a ad 3 b b bd bd 2 1 0 Depth Site btm top SCB btm top SCF btm top WRB btm top WRF Figure 4.3. Boxplot of peatland site and core depth against the von Post decomposition value. Where the centre horizontal line is the median, the box is bounded by the 75 th and 25 th percentiles (upper and lower) and the vertical lines indicate the 90 th and 10 th percentiles (upper and lower). Letters indicate significant difference. 4.2 Hydrologic Parameters 4.2.1. Saturated Hydraulic Conductivity 4.2.1.1. Laboratory The vertical and horizontal K SAT were significantly different in all four single parameters of climate, peatland type, microform type and core depth (Table 4.5, Table 4.6, Table 4.7). In the climatemicroform interaction of both the vertical and horizontal K, the WR hollows had the lowest K with both the SC microforms and the WR hummock K significantly higher (Table 4.7).The peatlandmicroform interaction was the same for the vertical and horizontal K with bog hollows significantly less than bog hummocks, and no significant difference in the fen microforms (Table 4.7). In Fig. 4.4 climate is separated by peatland then microform type (A and B). As in the climate-microform 30

interaction, WRB hollows had the lowest K however SCB hollows appear to approach these values. Overall, the general trend indicates that hummocks have higher K both vertically and horizontally, with the most pronounced difference in the bogs (peatland-microform interaction) (Fig. 4.4 A [One-way Anova, df: 45, F: 3.08, p: 0.011] and B [One-way Anova, df: 45, F: 3.94, p: 0.003]). The SC fen was not significantly different between microform types, however interesting to note is the apparent reversal of the general trend. The climate-depth interaction was the same for vertical and horizontal K, with the bottom cores of each climate (SC and WR) significantly lower than the top cores (Fig 4.4, C [One-way Anova, df: 45, F: 7.59, p: 0.000] and D [One-way Anova, df: 45, F: 6.80, p: 0.000]). In the horizontal K the peatland-depth interaction was also significant, with the same depth trend as the climate-depth interaction (Fig. 4.4, C and D). The vertical and horizontal K SAT were both highly correlated with bulk density (Ksat V, Pearson s Correlation: -0.77, p: 0.00; Ksat H, Pearson s Correlation: -0.78, p: 0.00). 31

Table 4.5. The vertical K SAT (cm s -1 ) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 4.74 0.39 btm 0.053 0.025 top 0.60 0.35 btm 0.010 0.0056 top 1.17 1.00 btm 0.031 0.018 top 3.66 3.09 btm 0.50 0.32 top 5.50 0.83 btm 0.19 0.13 top 0.060 0.060 btm 0.0091 0.0035 top 2.79 0.36 btm 0.067 0.0049 top 0.27 0.077 btm 0.046 0.017 Table 4.6. The horizontal K SAT (cm s -1 ) mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 4.71 0.31 btm 0.087 0.012 top 0.64 0.56 btm 0.020 0.0019 top 0.71 0.58 btm 0.051 0.13 top 2.86 0.23 btm 0.45 0.36 top 4.097 0.60 btm 0.26 0.35 top 0.057 0.039 btm 0.013 0.0062 top 1.44 0.20 btm 0.10 0.052 top 0.24 0.078 btm 0.092 0.053 32

Table 4.7. The general linear model F test statistic and p value for vertical saturated hydraulic conductivity (K SAT V; cm s -1 ), horizontal saturated hydraulic conductivity (K SAT H; cm s -1 ) and anisotropy of the vertical and horizontal hydraulic conductivity in the peat cores. Parameter KSAT V KSAT H Anisotropy F P F p F P Climate 10.54 0.003 11.31 0.002 1.37 0.25 Peatland 21.30 0.000 8.10 0.008 0.71 0.41 Microform 80.16 0.000 45.18 0.000 1.69 0.20 Depth 388.24 0.000 185.84 0.000 18.34 0.000 Climate x Peatland 3.25 0.08 0.14 0.70 2.40 0.13 Climate x Microform 54.87 0.000 28.51 0.000 6.37 0.017 Climate x Depth 10.48 0.003 5.70 0.023 0.14 0.71 Peatland x Microform 90.26 0.000 61.72 0.000 0.73 0.40 Peatland x Depth 4.02 0.05 4.57 0.041 0.91 0.35 Microform x Depth 24.42 0.000 13.60 0.001 0.33 0.57 Climate x Peatland x Microform 3.27 0.08 0.73 0.40 0.55 0.46 Climate x Peatland x Depth 6.74 0.014 1.10 0.30 4.59 0.040 Climate x Microform x Depth 0.97 0.33 0.74 0.40 0.12 0.73 Peatland x Microform x Depth 2.81 0.10 0.10 0.75 2.17 0.15 Climate x Peatland x Microform x Depth 2.52 0.12 0.09 0.77 0.55 0.47 33

A) ab a B) a ab ab ab ab a ab ab a a ab ab b b C) a abc a D) ac ab ab abc ab b bc b b c bc c c Figure 4.4. Boxplot of vertical and horizontal saturated hydraulic conductivity(k) where A) peatland site and microform type vs. vertical K, B) peatland site and microform type vs. horizontal K, C) peatland type and core depth vs. vertical K and D) peatland type and core depth vs. horizontal K. Median K is the centre line of each box. Box plots are bounded by the 75 th and 25 th percentiles and the centre line is median K, and letters indicate significant difference. 34

The microform-depth interaction of the vertical and horizontal K was significantly different (Table 4.7). In both vertical and horizontal K the top hummock cores had a higher K than the bottom hummock cores (Fig. 4.5, A [One-way Anova, df: 45, F: 27.50, p: 0.000] and B [One-way Anova, df: 45, F: 22.84, p: 0.000]). The hollow s follow the same trend, however it is less pronounced than in the hummocks. The three-way interaction of climate-peatland-depth was significant in the vertical K, though due to the complexity of the interaction, cannot be easily explained. A) a c B) a b b b b b Figure 4.5. Boxplot of microform type and core depth for vertical (A) and horizontal (B) saturated hydraulic conductivity, where median K saturated is the centre line of the box. The box is bounded by the 75 th and 25 th quartiles, the lines represent the 90 th and 10 th percentiles and circles indicate outliers. Letters above the boxes indicate significant difference. Anisotropy was significantly different with depth, with the bottom cores positive and the top cores negative (Table 4.7, Table 4.8). In the climate-microform interaction, WR hummocks were negative, whereas SC hummocks and hollows and WR hollows were positive (Table 4.7, Table 4.8). The climate-peatland-depth interaction was also found to be significantly different. The hollows, specifically the bottom cores had a more positive anisotropy than the hummock and top cores (Fig. 4.6). There is no apparent influence of peatland type on K anisotropy, with the general trend of more negative anisotropy in the top cores and more positive anisotropy in the bottom cores. The overall 35

average anisotropy of all cores was 0.034 with a standard error of the mean of 0.033. Anisotropy was not correlated with bulk density (Pearson s Correlation: 0.314, p: 0.08) Table 4.8. Anisotropy mean and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top -0.0020 0.020 btm 0.24 0.22 top -0.051 0.15 btm 0.33 0.27 top -0.099 0.22 btm 0.25 0.28 top -0.082 0.044 btm -0.064 0.15 top -0.13 0.033 btm -0.11 0.36 top 0.054 0.13 btm 0.12 0.057 top -0.029 0.11 btm 0.14 0.20 top -0.040 0.15 btm 0.28 0.13 36

Figure 4.6. Anisotropy of peatland site and core depth, where positive values indicate greater horizontal K than vertical, while negative values indicate greater vertical K than horizontal. 37

4.2.1.2. Field The saturated K recoveries from the piezometers were recorded for each microform type (Fig. 4.7). The hummock 50cm recovery was significantly higher than the lower depths (One-way ANOVA, df: 14, F: 9.23, p: 0.002), with a sudden decrease at the 100cm depth before returning to the original trend (Fig. 4.7). The hollow 50cm recovery was significantly higher than the 100-150cm, and consistently decreases with depth (One-way ANOVA, df: 14, F: 15.70, p: 0.000). There was no significant difference between hummock K with depth and hollow K with depth. Figure 4.7. The saturated hydraulic conductivity with depth from piezometer slug tests in hummock and hollow microforms at Wandering River Bog, where error bars indicate the standard error of the mean. 38

4.2.2. Water Retention and Pore Size Distribution 4.2.2.1. Water Retention Curves The water retention curves were separated into climate and peatland type for comparison. As pressure increased, the bottom cores of each microform type tend to retain more water than their top counterparts (Fig. 4.8). WR and SC bog (Fig. 4.8, A and C) maintained more consistent volumetric water content (VWC) with increasing pressure than the fens, where VWC showed a large decrease with increasing pressure. In general, the hummock surface retained the least VWC with increasing pressure, excluding SC fen, where the hollow surface retained the least VWC (Fig. 4.8, B) 39

A) B) C) D) Figure 4.8. The mean water retention curves from the pressure plate analysis for A) St. Charles bog, B) St. Charles fen, C) Wandering River bog, and D) Wandering River fen. 40

4.2.2.2. Pore Size Distribution Macropores empty at 3hPa with a diameter greater than 1 mm, mesopores may empty from 300-3 hpa, with a diameter range of 1-0.01mm, and micropores empty at pressures greater than 300 hpa with diameters less than 0.01mm (Carey et al., 2007; Luxmoore, 1981). The pore size distribution was separated into sample site (climate and peatland), before distribution s were plotted for each microform and core depth. The SCB and WRB hummock top cores were primarily composed of macropores, while the hummock bottom cores had a greater percentage of micropores (Fig. 4.9). In contrast the SCB and WRB hollow tops were primarily mesopores and the hollow bottoms were micropores (Fig. 4.10). The SCF and WRF hummocks followed the same trend as the bogs, with the top cores predominantly composed of macropores and the bottom cores dominated by micropores (Fig. 4.11). The SCF and WRF hollow top cores were primarily macropores, and the hollow bottoms were mesopores (Fig. 4.12). 41

A) B) C) D) Figure 4.9. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. A) SCB H top, B) WRB H top, C) SCB H btm, D) WRB H btm. 42

E) F) G) H) Figure 4.10. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. E) SCB W top, F) WRB W top, G) SCB W btm, H) WRB W btm. 43

I) J). K) L) Figure 4.11. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. I) SCF H top, J) WRF H top, K) SCF H btm, L) WRF H btm. 44

M) N) O) P) Figure 4.12. Frequencies of pore diameter distributions from pressure plate analysis. Pore diameter was calculated from Equation 3.6 (Carey et al., 2007), with macropores right of the vertical dashed line, mesopores left and micropores in dark grey on the far left. M) SCF W top, N) WRF W top, O) SCF W btm, P) WRF W btm. 45

4.2.3. Unsaturated Hydraulic Conductivity The initial saturation of the cores was not consistent, therefore to compare the unsaturated K values the slope of the VWC and unsaturated K was calculated. In Fig 4.13 and 4.14 the calculated slope closely follows the raw unsaturated K values. The r 2 values were over 0.90 for each slope calculation. 46

A) B) C) D) Figure 4.13. Unsaturated hydraulic conductivity with volumetric water content (VWC) where A) is SCB and WRB hummock top cores, B) SCB and WRB hollow tops, C) SCB and WRB hummock bottoms and D) SCB and WRB hollow bottoms. 47

E) F) G) H) Figure 4.14. Unsaturated hydraulic conductivity with volumetric water content (VWC) where E) is SCF and WRF hummock top cores, F) SCF and WRF hollow tops, G) SCF and WRF hummock bottoms and H) SCF and WRF hollow bottoms. 48

Table 4.9. The mean unsaturated K (cm s -1 ) and standard deviation (St. Dev.) of the mean for the main parameters of climate, peatland type, microform type, hummocks (H) and hollows (W) and depth of core. Climate Peatland Microform Depth Mean St. Dev. SC WR Bog Fen Bog Fen H W H W H W H W top 7.06 0.79 btm 4.56 1.60 top 4.98 0.69 btm 4.31 1.93 top 6.85 0.73 btm 7.27 0.98 top 4.84 0.78 btm 3.97 1.50 top 6.03 1.41 btm 2.72 0.66 top 4.26 1.93 btm 4.49 3.78 top 7.59 2.54 btm 8.06 0.74 top 3.23 0.53 btm 5.40 1.36 The GLM of the slope of the unsaturated K found that it varied significantly with both the single parameters of peatland and microform (Table 4.9, Table 4.10). The two-way interactions of peatland-microform and peatland-depth were also found to be significant. In the peatland-microform interaction, hummocks have a greater slope than hollows, with a greater difference observed in the fens than in the bogs (One-way ANOVA, df: 47, F: 3.96, p: 0.002) (Fig. 4.15). The peatland-depth interaction does not exhibit the same pronounced trend as the peatland-microform interaction (One-way ANOVA, df: 47, F: 1.42, p: 0.226). The bogs had a lower slope in the bottom cores than the surface, and there was no difference found in the fen top and bottom cores (Fig. 4.16). The unsaturated K slope was not significantly correlated with bulk density (Pearson s Correlation: -0.08, p: 0.57) 49

Slope (Log K Unsat vs. VWC) Table 4.10. The GLM F statistic and p values for slope of unsaturated hydraulic conductivity vs. volumetric water content. Parameter K Unsat F p Climate 0.31 0.58 Peatland 5.63 0.024 Microform 15.59 0.000 Depth 1.20 0.28 Climate x Peatland 1.65 0.21 Climate x Microform 0.03 0.87 Climate x Depth 0.73 0.40 Peatland x Microform 7.29 0.011 Peatland x Depth 5.18 0.030 Microform x Depth 2.41 0.13 Climate x Peatland x Microform 1.20 0.28 Climate x Peatland x Depth 0.33 0.42 Climate x Microform x Depth 1.60 0.22 Peatland x Microform x Depth 1.79 0.19 Climate x Peatland x Microform x Depth 0.12 0.73 10 a 9 8 ab ab b b 7 6 b b b 5 4 3 2 M/F Site H W SCB H W SCF H W WRB H W WRF Figure 4.15. Slope of the Log K unsaturated vs. VWC against peatland site and microform type, where the boxplot represents the 25 th and 75 th percentile, and the middle line is the median Slope. The 10 th and 90 th percentiles are the lower and upper vertical lines, respectively, and letters indicate significant difference. 50

Slope (Log K Unsat vs. VWC) 10 9 8 7 6 5 4 3 2 Depth Site btm top SCB btm top SCF btm top WRB btm top WRF Figure 4.16. Slope of the Log K unsaturated vs. VWC against peatland site and core depth, where the boxplot represents the 25 th and 75 th percentile, and the middle line is the median Slope. The 10 th and 90 th percentiles are the lower and upper vertical lines, respectively and outliers represented by *. 51

5. Discussion The peat cores, although all comprised of Sphagnum spp., displayed very different physical properties. The surface cores tended to be very loosely packed; with evident moss structure (Fig. 5.1).The cores located below the water table were highly decomposed, with only fibrous material maintaining definition (Fig. 5.1). The core extraction method was designed to obtain homogenous peat cores with no fibrous root material, and a single stage of peat decomposition. However, due to the nature of roots and the inability to predict the exact composition of the peat matrix, this was deemed an unrealistic expectation for all samples. Roots and fibrous material were kept to a minimum, to prevent the presence of large macropores influencing the hydrologic results. Figure 5.1. Peat cores from left to right, SCB W top, WRF H top, SCF H btm and WRB W btm. Decomposition of the peat increases from left to right, excluding WRB W btm where the upper half of the core is less decomposed than the lower half. 5.1 Hydraulic Conductivity Peatland hydraulic conductivity models use one value for K across the entire peatland microtopography and depths, or simply differentiate between microform types (Rietkerk et al., 2004; Swanson and Grigal, 1988). In the microform specific model where hummock K is assumed to be less than hollow K, K variability may lead to greater peatland patterning (Baird et al., 2009; Swanson and Grigal, 1988). Microform saturated K was found to be higher in the hummocks than the hollows, at 52