Forest Prairie Edge Read online

  First, a note about terminology. The Saskatchewan landscape covers a breadth of ecological diversity. It is too simple to say that there are only two major ecological areas, but despite obvious variations scholars argue that two effective ecosystems exist in the central Saskatchewan interior: boreal forest and grassland, commonly referred to as prairie. Where the two meet is often called the “parkland,” the aspen grove section characterized by black soil, trembling aspen, balsam poplar, and willow that lie in groves surrounded by medium and tall grasses.2 But the parkland is not the ecotone. In the late 1940s and early 1950s, researchers in the Department of Plant Ecology at the University of Saskatchewan, Robert Coupland and T. Christopher Brayshaw, argued that the ecotone is in fact the place where parkland and boreal forest meet.3 Ecologist Ralph Bird, whose 1961 book Ecology of the Aspen Parkland in Western Canada remains a major source of information on the flora and fauna of the middle parts of the western interior, reinforced Coupland and Brayshaw’s assertions. Bird argued that the effective ecotone was the “point of contact” between the parkland and the boreal forest and called it “an area of stress,” constantly in flux from one state to another.4

  Archaeologist David Meyer, after extensive work in the parkland and boreal forest regions of Saskatchewan, suggested that from an archaeological perspective the “grassland communities within the parklands are a northern extension of the plains grassland ecosystem” and that grassland and parkland were occupied as a unit by human inhabitants.5 The parkland has been misinterpreted to be the ecotone between the forest and the prairie, and its “importance … has become exaggerated,” Meyer declared.6 The parkland showed a variation and extension of grassland cultures; the meeting place between forest-adapted and prairie-adapted cultures was the forest fringe.

  I take the view that the ecotone is the boreal forest edge. Not only are there two major effective ecosystems, but also they are quite different from each other. The prairie has been consistently defined as treeless and arid, the boreal forest as well-treed and moist. It is in the contrast between the two that much of the tension and interplay of history has evolved.

  Prehistory

  The western interior of North America was covered in glaciers during the last ice age. During their retreat, glacial lakes formed at the receding edge. For about 400 years, from 11,300 to 10,900 BP, one of these lakes, glacial Lake Saskatchewan, covered what archaeologists call the Greater Forks region or what became the confluence of the North and South Saskatchewan Rivers. As the lake receded, the forks acted as a delta. The region would have looked rather like a shrub/tundra steppe, with large grazing animals. By 10,300 BP, white spruce advanced throughout the western interior, and the climate remained brisk because of the receding glaciers. In general, the cultural traces (spearpoints and other archaeological findings) point to the influence of southern culture on the local landscape.7 Over time, the boreal forest edge receded north. During the Altithermal period (6000 BP), a time of excessive dryness, the grassland pushed the forest edge to its northern apex at approximate latitude 59° north, almost to the northern boundary of current-day Saskatchewan. The cooling period following the Altithermal period allowed the boreal forest to advance southward to more or less contemporary conditions by about 4000 BP.8 Although this information might seem little more than archaic background, it does show that landscape changes on a grand scale can have significant local effects. The area under study has changed from glacier covered, to lakebed, to delta, to steppe, to spruce forest, to prairie, and back to boreal forest. It is important to contest the assumption that this place has always looked the way it does today.

  Forest Composition, Succession, and Fire

  At the north bank of the North Saskatchewan River west of the forks prior to settler and logging encroachment, dark pines and white spruce stood tall. Their near-impenetrable canopy presented a formidable wall of green stretching hundreds of miles toward the Canadian Shield. It was the southern edge of the Boreal Plain ecozone, which today accounts for nearly all of the commercial forest zone of Saskatchewan.9 The vegetation is officially classified as Mixedwood Boreal Forest. A mixedwood forest contains a mix of coniferous trees from white spruce to balsam fir on well-drained soils. When burned or logged, the mixedwood forest regenerates with trembling aspen and poplar. Jack pine trees are found in sandy soil zones, and black spruce, mosses, sedges, and tamaracks live on poorly drained areas known as muskegs (bogs).10 The kind of tree that inhabits a particular area corresponds directly to physiographic position (hillside, valley, north or south facing), soil texture (fine to coarse), and drainage. Black spruce, for example, grow best in peaty and wet places, white spruce prefer uplands and hillsides that are well drained, and jack pine are suited to sandy soils.11

  Scientist Henry Youle Hind visited the Saskatchewan forks region in 1858. Sent to the western interior to determine its suitability for farming, Hind recorded evidence of excellent soil and timber in the North Saskatchewan River valley. “Much of the timber,” he noted with dismay, “has been burnt, and the country is fast becoming an open prairie land.”12 According to the scientific thought of his time, successive fires would change a forested landscape to open prairie. Those who had travelled over the vast open prairie supposed that its treeless state was due not to aridity but to frequent fires. As renowned fire historian Stephen Pyne explained, fire was “often annual, nearly everywhere, [and] the flames were among the prairies’ defining feature. No other Canadian biota had so many fires so often and so widely cast.” As Pyne went on to question, “were those fires merely a property of the prairies … or, more boldly, were they a generative agent without which the grasslands could not exist, a flaming axe that hewed back the original forest?”13 The treeless state of the prairie, scientists suggested, was due to centuries of man-made burning, a cultural landscape as much as a physical one. There was no doubt, as observers at the time noted, that suppressing and stopping prairie fires resulted in a southward surge of the forest. 14 It stood to reason, then, that fire was indeed a “flaming axe” that hewed down or altered a wooded landscape.

  Ecological geographer Celina Campbell has suggested that the story of fire as the major factor in prairie creation/forest exclusion is incomplete. The plains region contained bison. Huge herds of animals browsed, ate, wallowed, trampled, and toppled aspen growth and churned the grassland to mud and dust. Using pollen analysis, Campbell and her colleagues argued that removal of the bison led to the expansion of aspen growth in the northern prairie, creating what is now known as the “parkland,” rather than the limited fire suppression practised by European and Canadian homesteaders toward the turn of the twentieth century.15 Campbell argued that three factors—drought (aridity), fire, and bison—had roles in creating and maintaining the extent of the open plains and that “the removal of any one of these limiting factors could have allowed aspen populations to expand.”16 The removal of two factors, bison and fire, in the past century and a half has allowed for a dramatic increase in aspen parkland. Ralph Bird also noted that there were “major fluctuations of the forest and grassland before the white man broke the land for agriculture.” Bird suggested that wet and dry periods were primarily responsible for the advance or retreat of aspen forest on a local or regional level. In general, the aspen forest would expand during a wet season and contract during a dry one, but at the micro level of sloughs the opposite would be true, as previously slough areas drying up would lead to aspen expansion, but excessive rain accumulation would lead to drowned and killed tree vegetation.17 Ultimately, I argue that (1) the parkland is part of the grassland ecosystem and (2) the parkland probably expanded following the removal of bison and fire from the prairie. It is possible that the problematic interpretation of the importance of the parkland region reflects the current physical, not historic, extent of the parkland.

  Just as fire has been an integral part of the grassland biome, so too the boreal forest is a fire-based ecological regime. Pyne, in his book on fir
e in Canada, claims that the breadth, size, and intensity of boreal fires “define Canada as a fire nation. Its boreal forest is to Canada what the arid Outback is to Australia.… With that flaming landscape, Canada becomes a global presence for earthly fire ecology.”18 Fire is one of three principal causes of boreal landscape fragmentation and regeneration, the other two lumbering and farming. The boreal forest, generally a green, cool, and wet biome, builds its reserves of biomass into juggernaut proportions. When a dry season hits, the boreal forest contains a magnitude of flammable timber and debris, peat and moss, shrubs and grasses. Factors that contribute to boreal fires include amount of available surface material, combustion properties, atmosphere, wind, moisture, lightning, anthropogenic interference, and fire frequency.19 The result is that boreal forest landscapes are almost always “mosaics of different ages resulting from the overburning of past fires.”20 These mosaic landscapes encourage and support different ages, stages, and types of biota, a pattern called succession. Within the boreal forest region north of Prince Albert, there are various succession patterns. In general, fire hazard is highest in jack pine stands, intermediate in spruce or fir stands, and low in hardwood (primarily trembling aspen) stands, except in a dry spring, when forest floor debris is particularly flammable.21

  A mixedwood boreal forest, consisting of both hardwood and softwood, can regenerate in several ways following a fire, depending on the intensity and length of the burn and the state and mixture of the parent stand. A hot burn, especially one that exposes mineral soil and retains access to an adjacent seed source, will seed in with conifers, both white and black spruce and jack pine. White spruce seeds well into the low canopy provided by young hardwood trees, which often overseed and crowd, resulting in a natural thinning process. In this instance, fire succession a few years after a burn shows a dense cover of aspen with white spruce seedlings. Jack pine, the most flammable of conifers, is adapted to fire and will regenerate densely. A lower intensity burn leads to aspen seedlings and poplar sprouts. Conifers grow more quickly than aspen, and by the time the forest reaches about sixty years following a burn the trees are co-dominant in the canopy, after which the aspen start to die out, and the stand reverts to conifers, though conifers suffer damage from being “whipped” by nearby deciduous trees.

  Consider also the age of a stand that burns. If a stand of trees that is not yet mature burns again, then the probability of conifer regeneration is limited, though aspen and poplar are less affected. If an area is repeatedly burned, then tree cover might revert to shrubland and grasses, with damaged or stunted hardwoods. If a mixedwood stand is burned and regenerates to aspen without any conifer source, then the stand might eventually reach its life span and degenerate into shrubs and brush (such as hazelnut, speckled alder, or willow in wet areas). To the eye, this landscape would most resemble parkland (bluffs separated by open, grassy fields). Thus, boreal forest fires, in particular cases, might encourage a reversion to parkland and eventually grassland—a phenomenon noted by early explorers and scientists such as Henry Youle Hind, proving that their assumptions were not far from the mark.22

  Human activity also changes boreal forest composition. Extensive logging creates an effect similar to low-intensity burns, which regenerate with aspen seedlings and, in time, conifer re-establishment (if a mature seed source remains). Logging, however, does not encourage rejuvenation of shrubs and plants on the forest floor. Extensive agricultural intervention re-creates the landscape more dramatically than logging or fire. In general, conifers are completely eliminated, used as firewood and building material. Poplar and aspen remain almost as weeds, repopulating themselves with ease at pond and river edges, in rockpiles, or in fields whenever agricultural pressure ceases. The overall effect of human intervention, either logging or agriculture, is a gradual physical change from a mixedwood boreal forest to a parkland/prairie resemblance.23 The parent boreal forest becomes physically and culturally subsumed.

  Fire is not always a natural process. In the boreal forest of the western interior of North America, First Nations cultures burned “corridors” or trails as well as “yards” or meadows.24 Burning a meadow encouraged fresh growth of grasses and sedges to entice moose, elk, or deer or to create fresh hay for horses. The young grass would also sustain mice and rabbits, which would bring predatory animals such as fox, lynx, and marten. One Beaver Indian woman from northern Alberta claimed that burning around sloughs was good for the muskrat population, which loved the tender new shoots.25 Moose and beaver browse new aspen growth. A burn in a sandy Jack pine forest would encourage a new growth of blueberries, a favourite crop for humans (and bears) in the north.

  Aboriginal forest inhabitants would not deliberately burn an organically rich, peaty, or mossy forest, for such fires tended to burn for a long period of time and were difficult to control. The majority of burns would be initiated in the early spring, when there were still pockets of snow on the ground, which would act as natural breaks. Burning in summer, with the risk of hot weather, high winds, and destructive crown fires, was not a part of traditional First Nations practice.26 Natural fires, lit by lightning when conditions were ripe, were in general the most destructive and out of control. Anthropogenic fires, unless carelessly lit or by accident, were generally more domestic, intended to groom the forest for certain purposes, particularly to encourage new plant growth for human or animal consumption. Large, destructive fires, however, had their human uses: for example, the young, straight pines found growing thickly a few years after a destructive burn could be harvested for teepee poles. Deliberate anthropogenic fires and harvest practices shaped the tenor of the forest and created commodities for human purposes.27 Between anthropogenic and natural fires, a forest would be a mosaic of many burns of different ages and scales. No matter how “wild” it might appear, the boreal forest developed as a human-shaped cultural landscape.

  Soils

  Soil creation is a complex process between the parent rock (or bedrock) and the vegetation that grows on that rock. This process is in constant flux and can change both from year to year and over centuries. A barren rocky area can be colonized by lichen and moss, which (over time) will decompose to form pockets of soil from which more complex plants, such as grasses and eventually trees, can take root. The parent rock within the north Prince Albert region is glacial till, a mixture of boulders, sand, silt, and clay deposited by glacial ice. In places such as the Sand Hills (now known as the Nisbet Provincial Forest), just north of Prince Albert, the parent rock is glaciofluvial, with coarse-textured deposits of sand and gravel. Archaeologists note that these sandbeds were laid down by water, both as part of the wind scouring of glacial Lake Saskatchewan and as the river formed a delta into that lake.28 Glaciolacustrine soils are stratified, their layers easily identifiable, with silt, clay, and sand. Formed at the bottom of glacial lakes, this parent rock can encourage soils more suited for agriculture. A wide pocket of glaciolacustrine soils can be found in the Shellbrook-Meath Park plain running in an east-west band just north of the Sand Hills.

  The Nisbet Provincial Forest shows the back-and-forth process between rock and colonizing vegetation. An area colonized by coniferous trees tends to have acidic soil, well leached by the trees. Conifers are evergreen trees, which do not shed their needles and so give little humus back to the soil. Deciduous trees such as trembling aspen and poplar, conversely, prefer a soil high in organic material. They contribute to the soil’s high organic content by dropping their leaves in fall. Across an area of a few hundred metres, soils can change over time, depending on both the parent rock and whether it has been colonized by one vegetation or another.

  Soil taxonomies common to the mixedwood boreal forest29 include brunisolic soils associated with jack pine forest; dark grey chernozemic soils that have a “salt and pepper” appearance of both light grey and black, common to the boreal transition zone; black chernozemic soils found in “pockets”; gleysolic soils found in regions of prolonged water
saturation, such as sloughs; organic soils, where deep layers of peat are present; and luvisolic soils, the classic forest soil that looks grey when disturbed or cultivated, leading to the common term “grey soil zone.” In general, the north Prince Albert region has three somewhat distinct bands of soil: brunisolic (sandy) soils just north of the city in the jack pine Nisbet Forest Reserve; chernozemic (dark grey and black agricultural soil) in the Shellbrook-Meath Park plain north of the pines; and the grey luvisolic or leached forest soil at the edge of cultivated land at the Northern Provincial Forest, stretching from Emma Lake in the west to Candle Lake in the east. The soil bands show a transition from sand to dark grey/black to, finally, leached grey luvisolic soil, generally considered unsuitable for agriculture.

  Physiography and Hydrology

  The physiography of the research region belongs to the Saskatchewan River Plain. The ground in the southern portion of the research area (the Nisbet Provincial Forest and the agricultural belt) is gently undulating to rolling. North and west toward Christopher and Emma Lakes and Prince Albert National Park, steeper slopes and well-drained soils of the Waskesiu Upland promote tree growth that has been particularly well suited to forestry exploitation. The majority of upland forest land is still owned by the Crown as part of the Northern Provincial Forest or the federal government as Prince Albert National Park.30