Home Social Landscape Featured Articles The Aspen Parkland: A Biological Preserve

The Aspen Parkland: A Biological Perspective

by W. Bruce McGillivray

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Trembling aspens are well-suited to parkland. They can withstand fire by producing suckers from horizontal roots even if the “mother” tree is destroyed. The characteristic uniform height of trees in Aspen groves reflects the common age of the individuals that likely developed from suckers after a disturbance. In many instances, the grove has a uniform genetic make-up as well, as all trees could be clones of the same parent. Aspen produce seeds every year (about 1.5 million from a mature tree produce the poplar fluff or “cotton” of late May or early June) but they require cool moist soil and no competition for light to germinate and grow. This combination is rarely found in parkland, hence the preferred form of reproduction is vegetative suckering (cloning). The genetic uniformity of aspen groves means that most trees in the grove look alike. Variation between groves is common, however, as they originated from different parents. The shape of the trees, bark colour (from white to grey), leaf size, and leaf shape can differ considerably among groves. In large stands of aspen, genetic differences in phenology (timing of flowering, leafing) are noticed in early spring when a group of trees are in leaf while the rest are just budding out.

As placid as a parkland scene may be, there is an ongoing battle being fought between the grasses and the aspens. After a fire, it is a race to see which can get to the sun first – grass or suckers – but grass usually wins. The large leaves of suckers, relative to those on a mature tree, are designed to be efficient light catchers. In wet years, though, the aspen can encroach relentlessly on the grasses, and in dry years the trees may hold their gains. Some suckers can appear 25 metres from the parent plant and grow 3 metres in a single year. Prolonged drought weakens aspens, however, and leaves them susceptible to fungus invasion. Groves can die and the grasses will take back their lost territory. Ideal growing conditions for Aspen are found in the southern mixed-wood boreal forest, just north of the Aspen Parkland. Ironically, most of the Aspen Parkland is a bit too dry for aspens to really thrive.

The history of the Aspen Parkland is one of competing interests. There is a tension between the trees and the grasslands. The local winner in these contests reflects long-term climatic conditions, as well as the effects of fire, topography, and serendipity. Other contests pit fur traders against the fur bearers; farmers, ranchers and engineers against nature; and loggers against common sense. These contests continue to be a feature of the parkland. There have been both winners and losers in these contests. Of the 7.35 million original hectares of Aspen Parkland in Alberta, 90 to 95 per cent has been altered or destroyed, primarily to support agriculture. Most remaining samples of original Parkland are less than 1,000 hectares in area and are on marginal soils. Morainal areas and those with solonetzic soils are relatively unproductive and have resisted development.

Contact with settlers has affected numerous animal populations. Early fur traders were remarkably efficient at eliminating fur bearers from the Parkland. After a few years in an area, catches declined and new areas were explored and trapped. Conservation was unknown. Bison (Bison bison) were gone by about 1870. They were soon followed by the wolf (Canis lupus), grizzly bear (Ursus arctos), and magpie (Pica pica). Beaver (Castor Canadensis) were virtually extinct by 1900. In fact, the turn of the century saw an all-time low in big game, including mule deer (Odocoileus hemionus), elk (Cervus elaphus), moose (Alces alces), and pronghorn (Antilocapra americana). Despite a relatively small population, there were enough Albertans hunting for food or commerce to essentially eliminate game. A lack of game meant anything else was worth eating, and species such as whooping crane (Grus americana), passenger pigeon (Ectopistes migratorius), prairie chicken (Tympanuchus cupido), and sharp-tailed grouse (T. phasianellus) were either eliminated or threatened with extinction. An irrational and misguided hatred of predators took its toll on hawks, owls, coyotes (Canis latrans), and badgers (Taxidea taxus), and left prey populations such as ground squirrels with few natural enemies.

For a number of reasons related to changes in animal populations, scarcity and value to collectors, and increasing leisure time, Albertans began systematic study of their natural world. Francis La Grange Farley settled in Camrose in 1907, at the age of 37, and spent a lifetime studying the birds of Alberta. He wrote hundreds of articles in local newspapers, but also published 36 scientific papers in peer-reviewed journals. His influence is still felt as the donor of many ornithological books to Provincial Museum of Alberta's library and as a mentor to the authors of the first Birds of Alberta.³ The value of his documented observations as a yardstick to measure change in our landscape is apparent from a 1919 paper by Percy Taverner, Dominion ornithologist, who recounted his 1917 collecting expedition to central Alberta. Taverner was thrilled at spotting (and as a good museum ornithologist, collecting) a black-billed magpie. He quoted Frank Farley: “No one knew this bird 10 years ago [yes, this is our ubiquitous magpie) …. I never saw or heard of one farther north than 10 miles from Camrose.”⁴

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