By Cassandra Schroeder, PAg, Range Management Extension Specialist, Kindersley
Healthy plant communities support forage production and ecosystem services on rangelands. The entire ecosystem relies on plants as the initial source of energy. Plants become feed for livestock, wildlife and insects which then support other animals and decomposers. The plant community is the most important indicator of range health, but distinguishing a healthy plant community from one that needs attention can be challenging.
One way to distinguish different plants is by their response to grazing. Range plants are often grouped into increasers, decreasers and invaders, based on how they respond to grazing. A plant community with a greater portion of decreaser species is healthier than one with lots of increasers or invaders.
Increasers are plants that increase with heavy grazing pressure. These plants often have adaptations like strong taste, spines, low growth habit or other characteristics that deter grazing. Some examples of common increaser species are pasture sage, low everlasting, golden rod and blue grama. Increaser species tend to be less productive and less desirable. This does not mean they are bad or problematic plants as increaser species are still part of healthy plant communities in small quantities. When they start to make a large portion of the plant community, they indicate problems and lack of rest.
Decreasers are desirable palatable plants that provide good forage. These plants are preferentially grazed and without proper rest, they can be overgrazed. If plants are overgrazed repeatedly, they slowly die off and are replaced by other species, decreasing in response to grazing. These types of changes usually happen over many years of selection pressure. Good grazing management can keep these decreaser species healthy by allowing enough rest for plant recovery.
Invaders are usually the weedy species that would be found on heavily disturbed areas. These are the type of plants that might be found around salt licks and oilers, but are not normally part of a healthy forage stand. Examples of some well-known species that are categorized as invaders are dandelion, broomweed and Canada thistle. Invaders also include exotic species that are not native to the prairies. Some of the exotic invaders, like leafy spurge, can cause a plethora of problems on rangelands if not controlled.
When evaluating the plant community, it is the proportion of increasers, decreasers, and invaders that is more important than the presence of single plants. Plant communities that are dominated by decreaser species, contain fewer increasers and limited invaders are generally healthy. They can capture energy and use resources to provide forage and support the rest of the ecosystem. For help identifying plants and understanding the plant community in your pasture, contact one of our range management extension specialists.