Ecological systems (ecosystems) consist of all the living organisms in an area and their physical environment (soil, water, air). Ecosystems are influenced over time by the local climate, variations in the local landscape, disturbances such as fire and floods, and the organisms that inhabit them. Grassland ecosystems in British Columbia generally occur in areas where the climate is hot and dry in summer and cool to cold and dry in winter, where the parent material is composed of fine sediments, and in valley or plateau landscapes. The organisms that live in grasslands include plants and animals that have adapted to the climatic conditions in a variety of ways. Differences in elevation, climate, soils, aspect and their position in relation to mountain ranges have resulted in many variations in the grassland ecosystems of British Columbia. The mosaics of ecosystems found in our grasslands, including wetlands, riparian areas, aspen stands and rocky cliffs, allow for a rich diversity of species.
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Components of Grasslands
Grassland ecosystems have both biotic and abiotic components. The biotic components of an ecosystem are the living organisms that exist in the system and can be classified as producers (including grasses, shrubs and trees), consumers (including grazing ungulates, birds and insects) or decomposers (including fungi, insects and bacteria). Abiotic components of the ecosystems are the non-living components on which the living components depend, including climate, soil and topography.
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Grassland Vegetation
Approximately 1,990 of types of vascular plants are found in plant communities that are dominated by steppe vegetation, which includes our native Bunchgrass Zone. This wide diversity of plant species requires managers to have a thorough understanding of plant physiology and morphology. Plants are generally grouped into six classes:
Trees
Trees can be either coniferous or deciduous. Coniferous trees, including Douglas fir and ponderosa pine, have needle-like leaves and seeds borne in cones. Coniferous trees are often referred to as “evergreens” because they retain their leaves throughout the year. Ponderosa pine is common as scattered trees on BC’s open grassland landscape or as semi-open stands. Douglas fir is abundant in swales and ravines, or in semi-open stands at higher elevations. On the upper grassland slopes, fire kept coniferous trees from encroaching and foresting the landscape. In recent decades as a result of fire suppression, vast acreages of the upper grasslands have been lost to forest.
Deciduous trees, such as trembling aspen, generally have broad, net-veined leaves and seeds that are produced from flowers. The leaves of deciduous trees usually change colour before they are shed in the autumn. Shrubs, such as Saskatoon and snowberry, are woody plants that have shorter, bushier appearances than trees. Aspen groves or ‘copses’ on the open grasslands and shrubby ravines or draws provide valuable food and cover habitat for wildlife and birds. Heavy grazing by cattle on these species competes with wild animals, such as deer, for forage. Cattle preference for browsing small aspen and deciduous shrubs in fall months can occur when protein levels in grasses are low.
Grasses
Grasses are herbaceous plants, which mean that they die back to ground level each year. The flowers and seeds of grasses can vary greatly and are used to distinguish between different grass species. Bluebunch wheatgrass and Rough fescue (found in steppe vegetation of the Southern Interior), pinegrass (found beneath forest canopies throughout central and southern BC) and Altai fescue (found in northern BC) are some common grasses of BC’s rangelands. The most palatable grass species for cattle and wildlife are more sensitive to grazing than weedy or annual grass species. Continued, heavy grazing can negatively impact the desirable grasses reducing their ability to compete with unglazed plants.
Grass-like plants
Sedges and rushes are similar to grasses in that they have slender, parallel-veined leaves, but their stems are unjointed and solid. Rushes have round stems and sedges usually have three-sided stems. Both sedges and rushes are associated mainly with wetlands but a number of sedges are also found in grasslands, forests and alpine areas throughout BC’s rangelands. Grazing values of sedges and rushes are quite high in spring months; however, this timing conflicts with the value of these species in the wetlands for nesting waterfowl habitat.
Forbs
Forbs are generally small plants that produce flowers. They flower at different times throughout the growing season and die back after flowering. Forbs are broad-leaved plants with fleshy stems and net-veined leaves. Yarrow, low pussytoes, lupines, arrow-leaved balsamroot and heart-leaved arnica are some of the common forbs in BC grasslands. The amount of forbs on the grassland landscape varies with site aspect, moisture and elevation. Although a seasonally spectacular when in flower, a high abundance of forbs can indicate that the sensitive grasses have disappeared from overgrazing.
Hazardous Plants
Plants that are either poisonous or injurious to livestock naturally exist in BC’s grasslands. Five species are considered to be major poisonous plants in BC: Seaside arrow-grass, tall larkspur, low growing larkspur, timber milk-vetch, and Douglas’s water hemlock. Poisonous plants are often unpalatable however grazing animals sometimes will be addicted to plants such as timber milk-vetch if animals are hungry and little good quality forage is available. The best way to avoid livestock poisonings is to be aware of the location and extent of poisonous plants in grazing areas. In addition to those poisonous, plants may also injure animals mechanically, such as the awns of cheatgrass and needlegrasses.
Cryptogams
Cryptogams are rather complex and have both visible and microscopic components that grow over the surface of soils. The visible part includes lichens, mosses and liverworts, while the microscopic component is made up of algae, fungi and bacteria. Because of this complexity, cryptogams are more commonly referred to as the microbiotic crust of soil surfaces. Some common lichens and mosses on BC’s bunchgrass ranges include pixie-cup lichens and rusty steppe moss. Crypotrams, or microbiotic crust, is sensitive to disturbance that occurs from motorized and non-motorized vehicles, human foot traffic, and animal hoof action. Overgrazing or recreational disturbances can result in a substantially reduced cover of cryptograms, reducing the soils nutrient and water functions. A lack of cryptogram crust and evidence of surface soil erosion indicates past soil disturbance or continued heavy use.
Detailed information on ecosystem processes such as nutrient cycling and energy flow, on the Understanding Grasslands pages.
For more information on plant communities, the animals that graze BC’s grasslands, or the effects of grazing on grassland plants, please choose one of the links below.
Plant Communities
Grazing Animals
Plant Responses to Grazing
Ecosystem Responses to Humans
Grassland Monitoring
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