Alberta Range Plants and Their Classification

Plants are the primary producers on rangeland, Range plants cluster in communities. Effective range management requires that plant communities, vegetation types, pastures, and finally ranches, be operated as range ecosystems.

A range ecosystem is a complex of living and nonliving (biotic and abiotic) factors of an environment where everything is connected to everything else. It functions as a unit and anything that affects one part of the unit, such as by grazing, affects the whole complex.

All the organisms within the community, the vegetation, the pasture, or the ranch affect each other, and, in addition, they also affect the abiotic or nonliving portion of the environment. A circular system of cause-effect relationships is thus set up in which the biotic fractions of the environment affect each other as, well as the abiotic. At the same time, the abiotic fraction affects the biotic. This continuum of interrelated cause-effect relationships is neverending as long as the habitat supports life in any form.

Thus, while the concept of the range ecosystem is complex, it is based largely on individual plants. It follows that, as range managers, we must know the plants, their structure and their habits.

Range plants, like people, have names. This name is the key to finding additional information about the plant. In addition to being named, range plants can be classified or grouped on the basis of growth form, lifespan, origin, response to grazing, and forage value. Plants with the same growth form are grouped into grasses, grass-like, forbs, shrubs, and trees. Life span differentiates between annual, biennial, and perennial plants, while origin refers to plants that are native to North America or are introduced from other continents. Plants grouped on the basis of response to grazing are divided among decreasers, increasers, and invaders. Palatability, or acceptability of plants by grazing animals, determines the forage value of the plants; these ratings are reported as good, fair, poor, or poisonous, the latter if plants contain toxic substances.

Range plants also can be classified as to the season of the year in which they make their best growth. Most of the plants listed in this bulletin show cool season response in that they make the major portion of their growth during spring and early summer. Some plants - Bouteloua gracilis, Andropogon scoparius, and Aristida longiseta - are classed as warm season plants because they grow slowly during the early part of the season and make their best growth in late spring and summer.

Definition of Plant Characteristics

Plant type
Grasses - plants which have hollow, jointed stems and leaves in two rows on the stems. The seeds are borne between two scales.
Grass-like plants - these look like grasses but have solid stems (not hollow) which are often triangular and have no joints. Veins are parallel in the leaves. These are sedges and rushes.
Forbs - broad-leaved plants with annual tops and net-like veins in the leaves (range weeds and flowers).
Shrubs - woody perennials with stems which live over the winter and branch from near the base.
Trees - woody, single-stemmed perennial plants which reach a mature height of at least 3 m.

Life span
Annual plants - live only for one season. They do not come up a second year from roots or crown.
Biennial plants - require two years to complete life cycle. Grow vegetatively during the first year and fruit and die the second.
Perennial plants - live over from year to year, producing leaves and stems for more than two years from the same root system.

Origin
Native plants - plants native to North America.
Introduced plants - those which have been brought in from outside North America - not present in the original vegetation.

Grazing response
Grazing response - how the various kinds of plants on the range react when they are grazed. This may vary with soil and climate for any one species. Range plants are grouped as follows:

• Decreasers - Highly productive, palatable plants that grow in the original climax vegetation stand. They are palatable to livestock, and will decrease on a range when exposed to heavy grazing pressures.
• lncreasers - These species are also native plants but they increase in site and number to take the place of decreasers which have weakened or died due toheavy grazing or other range abuse. The increaser plants are normally shorter, lower producing and less palatable to livestock.
• Invaders - These are plants which invade and replace the plants which have died or become seriously weakened. They may be annuals, perenials, or shrubs and have some or no grazing value.