The Effects of Mulches on the Microclimate of Disturbed ... · mosses and a few water plants. The...

The Effects of Mulches on the Microclimate of Disturbed Peatlands in the Hudson Bay Lowlands

By Nicole Ferguson

A thesis submitted in partial fulfillment of the requirements for the Bachelor of Science in Environmental Earth Science

Environmental Earth Science Programme Laurentian University Ramsey Lake Road Sudbury, Ontario

P3E 2C6

April 2008

© Nicole Ferguson, 2008

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Abstract:

Located in the Hudson Bay Lowland, the building and operation of De Beers’ Victor Mine will result in newly-created upland deposits and disturbed peatlands. One of the main hindrances to the revegetation of this area is the site’s sub-arctic climate. This study focuses on the ability of mulches to moderate the microclimate of the disturbed peat. During the summer of 2007 an experiment was set up on stockpiles of peat and clay. Over several weeks, air temperature, relative humidity, and soil moisture were measured under three densities of three local mulches (ericaceous shrubs, Carex straw, and fibric peat chunks) and two weed-free commercial mulches (straw matting, and coco matting). Statistical analysis of short term data for temperature and relative humidity showed some significant contrasts between the mulches, but the only consistent patterns were observed in the long term data. The long term data showed that the straw mulch moderated the temperature by an average of 2 ΕC. There was no difference in soil moisture content beneath any of the mulches compared to the control plot. This indicates that mulches may not be vital for revegetation efforts at this site.

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Table of Contents: Introduction ............................................................................................... 1 Peatlands ....................................................................................... 1 Disturbances and Rehabilitation ................................................... 1 Hudson Bay Lowland ................................................................... 1 Victor Project and its Disturbances .............................................. 2 Microclimates of Peatlands ........................................................... 2 Mulches ......................................................................................... 3 Objectives and Hypothesis ............................................................ 3 Methods .................................................................................................... 3 Study Site ...................................................................................... 3 Collecting the mulches .................................................................. 3 Setting up plots ............................................................................. 4 Collecting data .............................................................................. 5 Analyzing data .............................................................................. 6 Results ...................................................................................................... 7 Short Term Data ............................................................................ 7 Long Term Data .......................................................................... 11 WET sensor Data ........................................................................ 11 Discussion ............................................................................................... 27 Conclusion .............................................................................................. 29 Literature Cited ....................................................................................... 30

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Table of Figures: Figure 1: The Hudson Bay Lowland (shaded) covers 373 700

km2 along the west and south coasts of Hudson Bay .................................. 1 Figure 2: 1m2 plots of 12 treatments were set up in a complete

block design ................................................................................................. 5 Figure 3: Calibration graph of WET sensor readings with actual

water volume ................................................................................................ 6 Figure 4: Short Term Data – bar diagrams of significant

contrasts ..................................................................................................... 10 Figure 5: Long Term Data – Maximum temperature residuals

(against the average), July 12 – Aug 7 ......................................................... 12 Figure 6: Long Term Data – Minimum temperature residuals

(against the average), July 12 – Aug 7 ......................................................... 13 Figure 7: Long Term Data – Maximum relative humidity residuals

(against the average), July 12 – Aug 7 ......................................................... 14 Figure 8: Long Term Data – Minimum relative humidity residuals

(against the average), July 12 – Aug 7 ......................................................... 15 Figure 9: Long Term Data – Maximum temperature residuals

(against the average), Aug 9 – Aug 23 ......................................................... 16 Figure 10: Long Term Data – Minimum temperature residuals

(against the average), Aug 9 – Aug 23 ......................................................... 17 Figure 11: Long Term Data – Maximum relative humidity residuals

(against the average), Aug 9 – Aug 23 ......................................................... 18 Figure 12: Long Term Data – Minimum relative humidity residuals

(against the average), Aug 9 – Aug 23 ......................................................... 19 Figure 13: Long Term Data – Maximum temperature residuals

(against the average), Aug 31 – Nov 3 ......................................................... 20 Figure 14: Long Term Data – Minimum temperature residuals

(against the average), Aug 31 – Nov 3 ......................................................... 21 Figure 15: Long Term Data – Maximum relative humidity residuals

(against the average), Aug 31 – Nov 3 ......................................................... 22 Figure 16: Long Term Data – Minimum relative humidity residuals

(against the average), Aug 31 – Nov 3 ......................................................... 23 Figure 17: Long Term Data – Maximum temperature residuals

(against the open), July 12 – Aug 7 ............................................................. 24 Figure 18: Long Term Data – Maximum temperature residuals

(against the open), July 12 – Aug 7 ............................................................. 25

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Figure 19: Long Term Data – Maximum temperature residuals (against the open), July 12 – Aug 7 ............................................................. 26

Figure 20: Long Term Data – Maximum temperature residuals



(against the open), July 12 – Aug 7 ............................................................. 29

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Table of Tables: Table 1: Short Term Data – ANOVA results ................................................................. 8 Table 2: WET Sensor data - ANOVA results for soil water content ............................. 9 Table 3: Short Term Data - Significant Contrasts ......................................................... 9

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Figure 1: The Hudson Bay Lowland (shaded) covers 373 700 km2 along the west and south coasts of Hudson Bay

Introduction: Peatlands:

Peatlands are ecosystems where the biomass production exceeds the decomposition. In most cases this occurs because the soil is waterlogged creating an anaerobic environment where decomposition organisms can not survive. Even in these conditions peat still accumulates slowly at a rate of 0.5 – 1 mm per year. As a result it takes thousands of years for a peatland to develop (Quinty and Rochefort 2003). Sphagnum mosses are the dominate species in peatlands, but they also support many different species of vascular plants.

A natural peatland has a hummocky landscape, with two types of communities developing. The hollows between the hummocks are often waterlogged and support mosses and a few water plants. The hummocks support different species of mosses which grow in drier environments, as well as shrubs, grasses, and trees. Black spruce and tamaracks are the most common trees because they can survive in acidic, nutrient poor conditions (Abraham and Keddy 2005). Disturbances and Rehabilitation:

In temperate climates such as in Quebec and New Brunswick, peat is harvested to be used as a soil amendment. Peat mining involves digging ditches to drain the bog, and then systematically stripping the top meters of the peat deposits from the bog. This results in a landscape that has a drastically different hydrological regime, a complete change in topography, and in most cases, a loss of the seed bank (Quinty and Rochefort 2003). In Quebec less than 10% of abandoned cutover bogs have shown any sign of Sphagnum regeneration. Other temperate peatlands also lack the ability to self regenerate (Price 1996).

Revegetation of disturbed sites means that the area will be reseeded with vegetation that will create a sustainable environment. However it may not be with vegetation that made up the original environment of the location. Restoration is recreating the original vegetation of the location. In temperate areas, revegetation has often been assisted by mulches (Price, Rochefort and Quinty 1998; Quinty and Rochefort 1997). Past studies have shown that mulches moderate the temperature, and increase the soil moisture. Straw mulches have proven to be an essential part of peatland restoration in Southern Canada (Quinty and Rochefort 2003). Hudson Bay Lowland:

The Hudson Bay Lowland is the third largest wetland in the world. It covers 373 700 km2 along the western and southern shores of Hudson Bay and James Bay (Fig 1). The Hudson Bay Lowlands have some of the highest isostatic rebound on the North American Continent at 0.7-1.2 cm per year. Because of its large size the Hudson Bay Lowland is divided into three major ecological zones. These zones are dependent on climate, landforms, vegetation, and ecological processes. The three ecoregions are: Coastal Hudson Bay Lowland, Hudson Bay Lowland, and James Bay Lowland (Riley 2003). This experiment is set up in the James Bay

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Lowland ecoregion and therefore the following descriptions are all of that area. The climate of the overall Hudson Bay Lowland is characterized by short, cool

summers and cold winters. The James Bay Lowland in the southeast is slightly wetter and warmer than the average overall climate (Riley 2003; Abraham and Keddy 2005). The Hudson Bay Lowland has the highest density of wetlands in North America. The wetlands cover 76-100% of the area and over 90 % is a saturated peatland plain. Peat depth increases from depths of less than 3 m near the shore to up to 4 m in the interior. Depth is mainly a product of age. The interior wetland is mostly muskeg although it ranges widely from sedge, shrub and treed fens to open, shrub and treed bogs, with areas of swamp and shallow ponds, and lakes (Sjors 1963). The lowlands are drained by a dozen major and hundreds of minor rivers. The peak river flows occur in May and the lows occur in August. The lowlands support 816 native vascular plant species and 98 non-native species (Riley 2003). The flora is transcontinental but reflects its low-arctic and subarctic position. Approximately 300 bird species have been recorded in the Hudson Bay Lowland with migratory waterfowl species dominating (Abraham and Keddy 2005). Victor Project and its Disturbances:

De Beers Victor Project is located in the Hudson Bay Lowland near the community of Attapawiskat. It is Ontario’s first diamond mine and began its operation in early 2008, it consists of an open pit mine, cleaning site and facilities, and housing for staff, as well as water intake pipelines from nearby Attawapiskat river, and stockpiles of clay, peat, and used kimberlite. De Beers is required to revegetate the entire site when they close operations.

Disturbances at this site can be categorized into two broad classes. Winter roads, argo trails, and underground pipelines create relatively small changes in the hydrology and topography. They change the topography of the peatland either by cutting off the top of the hummocks to smooth out the area or by ruining the hummocks from repeated travel overtop of them by all-terrain vehicles. This kills/damages the vegetation on these hummocks and in the pools surrounding the hummock. The peat also becomes compacted and the top layer is churned up. In these places it may be possible to restore the disturbed sites to their original habitat.

The other major disturbance will be the stockpiles of peat, clay, and processed kimberlite created from the excavation of the open pit mine. These stockpiles are meters taller than the surrounding terrain and well drained. In the peat and clay stockpiles used in this study, the peat and clay has been mixed together, levelled, and graded. This creates upland deposits that are vastly different from the natural peatland habitats. It will be impossible to restore these disturbed sites to their original habitats, so the eventual goal is to revegetate them to upland habitats with natural grasses, shrubs, and trees. The revegetation project at the Victor site has to overcome the colder temperatures and shorter growing season which comes from being located in a sub-arctic climate. Microclimates of Peatlands: Microclimates are the specific climatic characteristics that are exhibited at a small scale in defined subsets of an environment. In natural peatlands, microclimates are created around the hummocks, and the depressions between them. There is a marked difference in the vegetation found in the two locations. Soil moisture is the main microclimate

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characteristic which differentiates between the two. The depressions are often flooded and therefore sustain different species of mosses then are found on the drier hummocks.

The microclimates for the disturbed peatlands are usually more uniform than found in natural habitats, especially on the raised peat/clay stockpiles that this experiment is located on. This is because the soils were levelled and graded when they were created. There is minimal microtopography. This experiment focuses on the microclimate at the soil-atmosphere interphase, most specifically the 2cm above and below the soil. This area has the most influence on the germination of seeds and mosses, and is therefore of great interest to revegetation efforts (Bristow 1988). Mulches: Mulches can be defined as a medium which increases the soil-atmosphere resistance to heat and vapour transfers (Bussiere and Cellier 1994). They have been used for agricultural purposes to modify soil temperature and water regimes in the seed zone (van Donk, et al. 2001). They have also been shown to decrease the amount of evaporation caused by wind and at the same time limit the amount or wind erosion and sediment loss due to water runoff (Quinty and Rochefort 1997). Under wet conditions there is no difference in temperatures between plots which have mulches and those that do not. However, as time increases between rain events, the differences in maximum temperatures increase. This has been linked to the pattern that soil moisture follows (Bristow and Horton 1996). Soils under straw mulches lose their moisture slower than bare soils.

Different mulches have different effects on temperature and moisture due to their differences in thickness, density, transmissivity, and porosity. The thicker a mulch the better its insulating effects and the more difference their will be between plots with mulches and plots without (Bristow 1988). Objectives and Hypothesis: The objective of this study was to analyze the effects that eleven mulches had on the microclimates on peat/clay stockpiles at De Beers Victor Site in the Hudson Bay Lowlands. The microclimate properties examined were air temperature, relative humidity, and soil water content. I also looked at how effective local mulches were in comparison to commercial mulches. I hypothesised that i) Mulches would significantly moderate the microclimate on peat-clay stockpiles in the Hudson Bay Lowland, and ii) that local mulches would be equivalent to commercial mulches in their ability to affect microclimate. Methods: Study Site: The site for this experiment was about 90 km inland from the community of Attawapiskat on James Bay (Figure 1). The plots were set up at 52o 48’ N and 083o 52’ W on graded and levelled peat/clay stockpiles. This area has an average temperature of -2 deg C, and receives 700-800 mm of precipitation annually. There is scattered permafrost throughout the region.

Collecting the Mulches:

Eleven mulches were chosen to be tested on peat/clay stockpiles at De Beers’ Victor Project in the Hudson Bay Lowlands. Eleven mulches were tested. Two commercial

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mulches were obtained from Terrafix erosion control blankets. These were Terrafix S31 weed-free Straw matting, (Straw) and Terrafix C32 Coconut matting (Coco). Nine local mulches were used: three densities of Carex Straw (Carex), three densities of ericaceous shrubs (Erics), and three densities of Peat chunks (Peat). The Carex mulches were local Carex aquatilis. The Erics mulches were a mixture of shrubs, mainly Ledum groenlandicum and Chamnedaphne calyculata, but also Vaccinium myrtillaides, Kalmia angustifolia, Kalmia polifolia, and Vaccinium ovalifolium. The Peat mulches were fibric peat collected from hummocks which had had their tops sheared off.

Carex: A location where Carex aquatilis was the dominant species was chosen.

The C. aquatilis was 60cm tall in this area. 1m2 sites were marked out and all the vegetation within each site was cut as close to the base as possible and tied into bundles. The bundles were transported back to the lab. Five 1m2 bundles were used for the Carex Standard density mulch. They were weighed and their average fresh mass was 575g. To get the Carex Low density mulch, 1m2 bundles were split in half. The average fresh mass of the Carex Low was 335g. Carex High density mulch was created by combining two 1m2 bundles. The average fresh mass of the Carex High was 1168g.

Erics: A location where the density of Ericaceous shrubs appeared to be similar was selected for collecting the Erics mulches. 1m2 sites were marked out on the tops of hummocks where the Ericaceous shrubs were growing. All vegetation within each site was cut as close to the base as possible and placed within separate garbage bags to be transported back to the lab and weighed. Unlike the Carex mulches, the Erics mulches were sorted into their mulch densities (Erics Low, Erics Standard, and Erics High) in the field. Half of a 1m2 square was placed into a garbage bag for the Erics Low. Two 1m2 squares were placed into a single garbage bag for Erics High. When they were weighed in the lab, the averages of each mulch density were measured to ensure that each mulch density had a similar fresh mass: Erics Low = 179g, Erics Standard = 358g, and Erics High = 744g.

Peat: The peat was collected off of an old winter runway where the top of the hummocks had been sheared off removing all the vegetation and leaving the fibric peat exposed. The fibric peat was cut with a knife into bricks that measured 20cm x 20cm x 20cm. Peat Low = one and a half bricks, Peat Standard = three bricks, Peat High = five bricks. Before being spread on the test plots the bricks were broken into fist-sized chunks.

Setting up the Plots:

Using a complete block design, five blocks were set up on graded and levelled peat/clay stockpiles. There were 12 treatments within each block (11 mulches + no mulch), each on a 1m2 plot. The treatments were assigned random locations within each block. Three of the blocks were set up on a south-facing slope and two of the blocks were set up on a north-facing slope (Figure 2). Each plot was marked with an aluminium tag with the correct treatment for that plot. The correct treatments were spread on each plot as evenly as possible (the Straw and Coco mattings were cut into 1m2 sheets). Metal pegs were used to hold down the corners of the Straw and Coco sheets so that they did not blow in the wind. A moderately heavy shower occurred during the setting up of the final plot, and heavy showers and thunderstorms passed through the region in the afternoon, so all the mulches received a thorough soaking.

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Figure 2: 1m2 plots of 12 treatments were set up in a complete block design

Collecting Data: Six dataloggers (Onset Corp U23 HOBO® Pro v2) were used to monitor air

temperature and relative humidity in 10 minute intervals. The sensors on the dataloggers were placed on 2cm above the soil surface and were not in contact with the mulches. Short term data was collected where the dataloggers were set up under the open, Coco, Straw, and the three densities of a local mulch (ex Carex Low, Carex Standard, Carex High) of the same block for 24 hour periods. The critical time for this experiment was between 11 am and 3 pm. If there had been no rain during the morning and that time period, the loggers were switched to another set of mulches. Long term data was collected over three different intervals (July 11 - July 7, Aug 9 - Aug 23, and Aug 30 - Nov 3) During these time periods the loggers were placed under the open, Straw, Coco, and one density of the three local mulches (ex Carex Standard, Erics Standard, Peat Standard) on the same block.

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A WET sensor probe (Delta-T Devices Ltd, WET Sensor type WET-2 and Moisture

Meter type HH2) was used to measure percent water volume at 2 cm depths. The WET sensor readings were taken on three different dates over the summer: July 7th, Aug 7th, and Aug 23rd. The WET sensor readings were calibrated with samples from the peat/clay stockpile which were analyzed in the lab for percent water volume (The samples were taken in 255cm3 cores. They were weighed, and then dried overnight in a 105ΕC oven. The masses were weighed again to calculate the water loss. The percent water volume was then calculated and plotted against the water volume recorded by the WET sensor in the field (Figure 3)).

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Analyzing Data:

Four hour periods in the middle of the day were separated out of each of the short term temperature and relative humidity data for each plot. This was done because these hours were undisturbed by rain events (the data was retaken if there were rain events during these periods). These four hour periods were analysed using univariate ANOVAs in SPSS. Each group of six dataloggers were analyzed together, so in the results, Carex refers to the Open, Coco, Straw, Carex Low, Carex Standard, and Carex High. Erics refers to the Open, Coco, Straw, Erics Low, Erics Standard, and Erics High. Peat refers to the Open, Coco, Straw, Peat Low, Peat Standard, and Peat High. Five contrasts were then analysed. These were: 1) no mulch vs all the mulches, 2) local mulches vs commercial mulches, 3) Coco vs Straw, 4) a linear contrast of the three local mulches, and 5) a quadratic contrast of the three local mulches.

For the long term data the daily maximum and minimum values for temperature and relative humidity were analyzed. The residuals of the extreme values were taken against the average of the six treatments, as well as against the no mulch plot.

The soil moisture taken with the WET sensor was analyzed using univariate ANOVAs in SPSS. Eleven contrasts were then examined. The contrasts were: 1) open vs all the others, 2) Coco vs Straw, 3) local vs commercial, 4) Peat vs Erics and Carex, 5)

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Erics vs Peat and Carex, 6) a linear contrast of the Peat, 7) a quadratic contrast of the Peat, 8) a linear contrast of the Erics, 9) a quadratic contrast of the Erics, 10) a linear contrast of the Carex, and 11) a quadratic contrast of the Carex.

Results: Short Term Data:

Minimum temperature: Only the Erics mulches and the Peat mulches had significantly different minimum temperatures (Table 1c). From the contrasts, the local Erics mulches were higher than commercial mulches (Table 2, Fig 4n), and the no mulch temperature was higher than that of the Coco, Straw, and three densities of Peat mulches (Table 2, Fig 4k). Also, the minimum temperature decreased with increasing densities of the Peat mulches (Table 2, Fig 4j).

Maximum temperature: Based on the complete ANOVAs, none of the mulches created significant differences for the maximum temperature (Table 1b). However, based on the contrasts, the Coco had a significantly higher maximum temperature than the Straw (Table 2, 4b), and Open plot had a higher maximum temperature than the Coco, Straw, and the three densities of Peat mulches (Table 2, Fig 4i).

Average temperatures: The average temperatures were significantly different in the experiments with the Erics mulches and the Peat mulches (Table 1a). From the contrasts, the three densities of Erics mulches had higher average temperatures than the commercial mulches (Table 2, Fig 4o). As well, the contrasts show that average temperature decreased with increasing densities of the Peat mulches (Table 2, Fig 4l). The Open plot also had a significantly higher average temperature than Coco, Straw, and three densities of Peat mulches (Table 2, Fig 4m). Another contrast was significant with regards to average temperature. The three densities of the Carex local mulch were higher than the commercial mulches (Table 2, Fig 4a).

Minimum relative humidity: Overall, based on the ANOVAs none of the mulches created significant differences for the minimum relative humidity (Table 1d). However, based on the appropriate contrast, the Coco had a lower relative humidity than the Straw mulch (Table 2, Fig 4e, 4h). Surprisingly, the open plot had a higher minimum relative humidity than the average of the Coco, Straw, and the three densities of Carex (Table 2, Fig 4d). Also, the minimum relative humidity decreased with increasing densities of the Carex mulches (Table 2, Fig 4f).

Maximum relative humidity: Overall, based on the ANOVAs, none of the mulches created significant differences for the maximum relative humidity (Table 1e). However, based on the appropriate contrasts, the three densitities of Carex mulches had lower relative humidities than the commercial mulches (Table 2, Fig 4g).

Average relative humidity: The average relative humidity was significant under the Carex mulches (Table 1d). From the contrasts, the three densities of the Carex mulches had significantly lower average relative humidities than the commercial mulches (Table 2, Fig 4c).

Despite the fact that several significant results were obtained from the short term data, there is no consistent pattern evident in these results.

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Table 1a: Short Term Data - Average Temperature Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 90.771 58.648 0.000 129.978 569.339 0.000 132.076 360.141 0.000 Treatment 1.581 1.022 0.431 3.232 3.232 0.027 1.258 3.429 0.021 Error 1.548 - - 0.228 - - 0.367 - - Table 1b: Short Term Data - Maximum Temperature Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 136.716 67.479 0.000 168.823 261.951 0.000 118.110 111.096 0.000 Treatment 1.725 0.852 0.530 1.107 1.718 0.177 2.235 2.103 0.107 Error 2.026 - - 0.644 - - 1.063 - - Table 1c: Short Term Data - Minimum Temperature Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 51.565 31.035 0.000 90.351 250.620 0.000 102.962 319.613 0.000 Treatment 1.758 1.058 0.412 1.561 4.331 0.008 1.129 3.506 0.019 Error 1.662 - - 0.361 - - 0.322 - - Table 1d: Short Term Data - Average Relative Humidity Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 325.107 13.359 0.000 558.119 16.115 0.000 1155.406 105.495 0.000 Treatment 35.322 1.451 0.250 35.566 1.027 0.429 9.035 0.825 0.547 Error 24.336 - - 34.633 - - 10.952 - - Table 1e: Short Term Data - Maximum Relative Humidity Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 240.436 13.137 0.000 281.071 10.067 0.000 942.824 66.441 0.000 Treatment 25.453 1.391 0.270 52.522 1.881 0.143 11.558 0.815 0.553 Error 18.302 - - 27.919 - - 14.190 - - Table 1f: Short Term Data - Minimum Relative Humidity Carex Erics Peat

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 717.150 52.286 0.000 861.107 16.089 0.000 1529.731 106.325 0.000 Treatment 53.040 3.867 0.013 47.274 0.883 0.510 26.825 1.865 0.146 Error 13.716 - - 53.523 - - 14.387 - -

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Table 2: WET Sensor data - ANOVA results for soil water content 07-Jul-07 7-Aug-2007 23-Aug-07

Source Mean

Square F p Mean

Square F p Mean

Square F p Block 41.296 5.308 0.001 83.880 6.913 0.000 61.507 7.364 0.000 Treatment 5.725 0.736 0.699 6.430 0.530 0.872 8.525 1.021 0.445 Error 7.780 - - 12.134 - - 8.352 - -

Table 3: Short Term Data - Significant Contrasts Variable Contrast P Carex AvgT Local vs Commercial 0.022 Carex MaxT Coco vs Straw 0.000 Carex AvgRH Local vs Commercial 0.046 Carex MinRH Open vs Others 0.013 Carex MinRH Coco vs Straw 0.046 Carex MinRH Linear 0.016 Carex MaxRH Local vs Commercial 0.022 Erics AvgT Local vs Commercial 0.003 Erics MinT Local vs Commercial 0.000 Peat AvgT Open vs Others 0.007 Peat AvgT Linear 0.041 Peat MinT Open vs Others 0.007 Peat MinT Linear 0.044 Peat MaxT Open vs Others 0.033 Peat MinRH Coco vs Straw 0.033

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Long Term Data: With the long term data, the mulch which had the most consistent data was the

Straw mulch. For all three time periods, the maximum temperatures were all below the average, and the minimum temperatures were all above the average (Fig 5c – 10c). This is also true when compared to the open plot. The maximum temperatures under the Straw during the day were on average two degrees lower than the maximum temperatures of the open plot. The minimum temperatures under the Straw at night were on average one degree warmer than the minimum temperature of the open plot (Fig17b – 22b).

The Coco mulch consistently raised the minimum temperatures at night by an average of 1 degree Celsius above the temperature on the open plot (Fig 18a, 20a, 22a), however during the day the Coco mulch was less predictable. From mid July to early August, the maximum temperatures under the Coco mulch were usually above the average although it ranged from -0.5 degrees below to 3.0 degrees above the average (Fig 5b). During late August the maximum temperature under the Coco showed no trend, with temperatures ranging from -1.0 below to 1.0 above the average (Fig 7b). During September, October, and the start of November, the maximum temperature stayed mainly below the average although there was still variation from -1.5 below to 0.5 degrees above the average (Fig 9b).

The Carex Standard mulch raised the maximum temperature above the average during the day, and lowered the minimum temperature below the average during the night (Fig 7d-10d). The most noticeable trend in the Carex Standard is that during August and the first half of September, the maximum temperatures were around 2 degrees above average, but during the second half of September the variation lessened until by October the maximum temperatures under Carex Standard reflected the average maximum temperatures (Fig 7d, 9d). In relation to the Open plot, the maximum temperature under Carex Standard was 2 degrees warmer than the open plot in August, but 1 degree cooler by the end of September (Fig 19c, 21c)

The Erics Standard shows no pattern of moderating the temperature. During the day its maximum temperature is either above or below the average, and during the night its minimum temperature is lower than the average (Fig 7e – 10e). There is no consistent pattern in relationship to the Open plot.

Peat Standard does not show any consistency in how it affects the temperature. During August, Peat Standard moderated the maximum temperature in the day, but exaggerated the minimum temperature at night. During September and October, Peat Standard exaggerated the maximum temperature during the day and the minimum temperature at night (Fig 7f – 10f, 19e – 22e). The maximum and minimum relative humidity residuals showed different ranges of variations. The maximum relative humidity residuals were usually between 2.0% above and 2% below the average with no definite patterns for any of the mulches (Fig 11, 13, 15). The minimum relative humidity residuals had greater variations, ranging between 15% above and 15% below the average (Fig 12, 14, 16). However Straw was the only mulch which consistently raised the minimum relative humidity above the average (Fig 16c) WET Sensor: There was no indication of any differences in soil moisture under any of the mulches (Table 2).

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Figure 1: Long Term Data – Maximum temperature residuals, July 12 – Aug 7

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11-Jul 21-Jul 31-Jul 10-Aug

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11-Jul 16-Jul 21-Jul 26-Jul 31-Jul 05-Aug 10-Aug

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a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 2: Long Term Data – Minimum temperature residuals, July 12 – Aug 7

-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 7: Long Term Data – Maximum relative humidity residuals, July 12 – Aug 7

-2

0

2

4


-2

0

2

4


-2

0

2

4


-2

0

2

4


-2

0

2

4


-2

0

2

4


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 8: Long Term Data – Minimum relative humidity residuals, July 12 – Aug 7

-16-808

16


-16-808

16


-16-808

16


-16-808

16


-16-808

16


-16-808

16


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 9: Long Term Data – Maximum temperature residuals, Aug 9 – Aug 23

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08-Aug 13-Aug 18-Aug 23-Aug

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a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 10: Long Term Data – Minimum temperature residuals, Aug 9 – Aug 23

-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 31: Long Term Data – Maximum relative humidity residuals, Aug 9 – Aug 23

-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


-2-1012


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 14: Long Term Data – Minimum relative humidity residuals, Aug 9 – Aug 23

-14-707

14


-14-707

14


-14-707

14


-14-707

14


-14-707

14


-14-707

14


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 13: Long Term Data – Maximum temperature residuals, Aug 31 – Nov 3

-3

0

3

30-Aug 09-Sep 19-Sep 29-Sep 09-Oct 19-Oct 29-Oct 08-Nov

-3

0

3


-3

0

3


-3

0

3


-3

0

3


-3

0

3


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 14: Long Term Data – Minimum temperature residuals, Aug 31 – Nov 3

-3

0

3


-3

0

3


-3

0

3


-3

0

3


-3

0

3


-3

0

3


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 15: Long Term Data – Minimum relative humidity residuals, Aug 31 – Nov 3

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1015


-15-10

-505

1015


-15-10-505

1015


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-505

1015


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1015


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1015


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 16: Long Term Data – Maximum relative humidity residuals, Aug 31 – Nov 3

-4

-2

0

2

4


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-4

-2

0

2

4


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-4

-2

0

2

4


-4

-2

0

2

4


a) Open

b) Coco

c) Straw

d) Carex

e) Erics

f) Peat

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Figure 17: Long Term Data – Maximum temperature residuals, July 9 – Aug 7

Figure 18: Long Term Data – Minimum temperature residuals, July 9 – Aug 7

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Figure 19: Long Term Data – Maximum temperature residuals, Aug 9 – Aug 23

Figure 20: Long Term Data – Minimum temperature residuals, Aug 9 – Aug 23

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Figure 21: Long Term Data – Maximum temperature residuals, Aug 30-Nov 2

Figure 22: Long Term Data – Minimum temperature residuals, Aug 30-Nov 2

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Discussion: It appears from the short term data, that mulches do not have a significant affect on the microclimate at this site. For the majority of the short term data variables there was no significance. The average temperature and minimum temperature were significant for the Erics mulches and the Peat mulches, but not for the Carex mulches. The minimum relative humidity was significant under the Carex mulches. This indicates that the mulches used have more of an affect on the temperature than on the relative humidity. The short term data was taken from four hour periods. It is possible that significance might show up if longer periods were used, but for this study the time periods were chosen because they were rain-free. Rain affects how well the mulch works. Studies have shown that mulches have minimum effect directly after rainfall (Bristow 1998; Bussiere and Cellier 1993). In those studies the maximum temperatures converged after a rain event. Greater moderation of the maximum temperature was observed after several days of drying had occurred. During the time the short term data was collected for this study there were rain showers every couple of days, and a few major storms passed through the region. This means that although it was sunny when the data was recorded, the full effects of the mulches might not have been shown. However, assuming 2007 was a typical summer for the Attawapiskat region with plenty of rain showers, then the data obtained is representative for this area. Overall the short term contrasts did not display any consistent significant variables, but within the variables that were significant there were some patterns. The temperatures under local mulches were higher than the temperatures under the commercial mulches. This is consistent with the long term data that shows that the commercial mulches moderated the temperatures more than the local mulches. Related to this, the commercial mulches had higher relative humidities than the local mulches because the cooler temperatures created by the mulches can not hold as much moisture. So if there is the same amount of water vapour everywhere in the air, the cooler air under the commercial mulches results in the higher relative humidity.

The Coco vs Straw contrast was only significant once for maximum temperature (Coco was higher than Straw), and twice for minimum relative humidity (Straw was higher than Coco). This contrast should have had the most consistency because the Straw and Coco mulches never changed no matter what local mulches they were being measured with. If the mulches reliably affected the microclimates they the Straw vs Coco contrasts would be significant for all three minimum relative humidities (the time Coco and Straw were measured with Erics, the time they were measured with Carex, and the time they were measured with the Peat). Because this does not occur, and because there are no other strong patterns observed, I conclude that the mulches do not reliably affect the microclimate, at least based on my short term data. In comparison to the short term data, the long term data shows more conclusive data. The trends observed on the residuals plots indicate that the commercial mulches moderate the temperature, while the local mulches tested did not have an effect. The behaviour of the temperature under the Straw mulch, with lower maximum temperatures during the day, and higher minimum temperatures at night, is in accord with the findings of Price (1998), who also found this moderating affect that Straw mulch had on temperature. Quinty and Rochefort (2003) found differences of up to 10 degrees Celsius between Straw

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mulches and open plots, but I was only observing an average difference of 2 degrees Celsius with a maximum difference of 4 degrees Celsius.

The Coco mulch behaved similarly to the Straw. It also moderated the temperature at night, but in contrast to the Straw mulch, its maximum temperatures were not moderated during the warmest months of the summer. During July and August, when the temperatures were warmer, the Coco matting exaggerated the maximum temperatures, making them even warmer than on the open plot. During September and October, when the daily temperatures were cooling down, the Coco mulch reacted similarly to the Straw and moderated the maximum temperatures.

The local mulches showed no consistency in how they affected the temperature. They all lowered the nightly minimum temperatures by up to 0.5 degrees. However during the day the local mulches were either above or below the average maximum temperature in no particular pattern. During August, the peat chunks lowered the maximum temperature by up to 2.5 degrees below the open plot, but during September the Peat chunks raised the maximum temperature by 1 degree above the open plot. This difference in whether the maximum temperature was raised or lowered on the Peat plot may be an artefact of the placement of the datalogger which was switched between August and September. Peat mulch controlled the temperature by the amount of shade the Peat chunks produced. The data collected may be explained if the datalogger was placed closer to a Peat chunk in such a way that it was shaded for a greater proportion of the time in August than it was in September and October. The shading would lower the maximum temperature during the day as displayed for August, but would not have any affect at night because there is no shade created. The placement of the dataloggers may also have affected the data for the Carex and Erics mulches if the thickness or density above the sensor changed between the two time periods. However the density of the Coco and Straw mulches were more evenly applied, so there should have been less variation between the two time periods. During the July 12 – August 7 time period, data was collected from under Carex High, Erics High, and Peat High. During the August 9 – August 23 time period, data was collected from under Carex Standard, Erics Standard, and Peat Standard. The only difference which appeared between the different densities of local mulches was under Erics Standard and Erics High. For the minimum temperatures, Erics High had residuals which were higher than the average, and Erics Standard had residuals which were lower than the average. This could possibly be explained by the differences in thickness and density. Bristow (1988) looked at the effects of different thicknesses of a Stylosanthes hamata mulch, and found that more open canopies (less dense) did not trap as much heat. So for this study, because Erics High was denser and thicker the heat was trapped better beneath the mulch which led to the maximum temperatures being higher than normal. Erics Standard would not have been dense enough to hold onto the heat and the temperatures were lower than the average. The patterns seen in the long term data becomes important when the revegetation of these sites occurs. Seeds will germinate and mosses propagate within an optimum range of temperatures and other climatic variables. If the temperature becomes too hot, there is a greater chance of the mosses or seedlings drying out. If the temperatures are too cold germination may not take place, or needle ice formation may destroy newly grown roots. The purpose of the mulches is to create a microclimate that stays within the optimal range for the greatest length of time. The Straw mulch and the Coco mulch keep the temperature above freezing for the longest. In 2007, the first day the temperature dipped below freezing

Ferguson 29

(0 degC) on the open plot was August 19. The temperatures under Carex, Erics, and Peat dropped below 0 deg C on August 20. The temperature under Straw did not drop below 0 deg C until September 9, and the temperature under the Coco mulch stayed above 0 deg C until September 13. If you are looking to keep the temperature above freezing the longest, then Coco is the mulch you would use. However during the hottest days, Coco raises the temperature. On July 22, 2007 the temperature under the Coco mulch reached 41 deg C, four degrees hotter than the open plot. If this is above the optimal range for revegetation, then the benefits from extending the non-freezing period might be negated. The Straw mulch might be an effective mulch because it kept the temperature above freezing for a longer period of time, and it moderated the maximum temperature on the hottest days. The lack of difference in near surface soil moisture under any of the mulches versus the open plots is also surprising. This is very different from results found in studies conducted in temperate peatlands. Price (1997) recorded soil water levels that were 10-15% higher under Straw mulch than on plots where there was no mulch. The increased soil moisture found in the seed zone under mulches in temperate peatlands is an important aid for seed germination (Bristow 1988). In this study there was no significant variations in the water content of the soil under the different mulches. This means that seed germination at this site would not receive any additional benefits from mulches. Conclusion: Although when we looked at the short term data for this experiment there were some significant contrasts, there were no overall patterns in either temperature or relative humidity. The long term data showed that the Straw mulch moderated the temperature the most, followed by the Coco mulch. The local mulches were less predictable, and often exaggerated the temperatures instead of moderating them. No patterns were observed for relative humidity. The mulches had no affect on the soil water content as measured at the three times over the summer. These results show that mulches may not have any beneficial effects in the revegetation efforts at this site. However, further studies are needed to determine if mulches prevent frost heaving or needle ice formation, or if mulches will prevent seeds and diaspores from being desiccated by the wind.

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Literature Cited: Abraham, K., and Keddy, C., 2005. The Hudson Bay Lowland. in The World’s Largest

Wetlands: Ecology and Conservation. Cambridge University Press. New York. Bristow, K., 1988. The role of mulch and its architecture in modifying soil temperature.

Australian Journal of Soil Research. 26, 269-280. Bristow, K.. and Horton, R., 1996. Modeling the impact of partial surface mulch on soil

heat and water flow. Theoretical and Applied Climatology. 54, 85-98. Brussiere, F., and Cellier, P., 1994. Modification of the soil temperature and water content

regimes by a crop residue mulch: experiment and modelling. Agricultural and Forest Meteorology. 68, 1-28.

Price, J., 1996. Hydrology and micrclimate of a partly restored cutover bog, Quebec.

Hydrological Processes. 10, 1263-1272. Price, J. 1997. Soil moisture, water tension , and water table relationships in a managed

cutover bog. Journal of Hydrology. 202, 21-32. Price, J., Rochefort, L., Quinty, F., 1998. Energy and moisture considerations on cutover

peatlands: surface microtopography, mulch cover and Sphagnum regeneration. Ecological Engineering. 10, 293-312.

Quinty, R., and Rochefort, L., 2003. Peatland Restoration Guide, 2nd ed. Canadian

Sphagnum Peat Moss Association. Alberta. Accessed on March 20, 2008. Available at http://www.peatmoss.com/pdf/Englishbook.pdf

Riley, J., 2003. Flora of the Hudson Bay Lowland and its Postglacial Origins. National

Research Council of Canada. Canada. Rochefort, L., Quinty, R., and Campeau, S., 1997. Restoration fo peatland vegetation: the

case of damaged or completely removed acrotelm. International Peat Journal. 7, 20-28.

Sjors, H., 1963. Bogs and Fens on Attawapiskat River, Northern Ontario. in Fens and

Bogs: Environmental conditions, phytosociology, and land level observations. van Donk, S., Tollner, E., and McDonald, S., 2001. Development of hot/cold plate

apparatus for determining heat transport mechanisms in mulch materials. American Society of Agricultural Engineers. 44, 1479-1488.
http://www.peatmoss.com/pdf/Englishbook.pdf�

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