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Submodule 1: What are invasive weeds?

Why Should We Care About Western Rangeland Weeds?

Western rangelands are rich natural resources that provide food and fiber production, recreational areas, nutrient and water cycling, wildlife habitat, and vast natural diversity. They make up about 40% of the U.S. landmass as a whole with over 80% of western lands classified as rangeland. These are diverse lands comprised of several different landforms in a variety of climate conditions. Many factors influence rangeland ecosystem characteristics including amount of sunshine and precipitation, wind speed, temperature extremes, and soil nutrient content. Grasses, herbaceous forbs, and shrubs dominate natural vegetation and are used to classify rangelands. They are generally thought of as grazing lands for livestock and wildlife. Because of the integral part rangelands play in natural ecosystems and in economic health, their well-being is of great interest to researchers, policymakers, and the public. Almost half of these open spaces in the western U.S. are owned and managed by the federal government.

 

Western rangelands have been grazed by wildlife and/or livestock for hundreds of years. More recently, recreation has become increasingly important as the western U.S. becomes more urban. Unfortunately, a significant portion of western rangeland has been overused and poorly managed. These issues, along with unfavorable weather conditions, contributed to the deterioration of rangeland soil quality and watersheds in some areas. Grazing can have both positive and negative effects on rangeland depending on whether grazing animals are managed properly or improperly.

Positive impacts of grazing

• Removes dead plant material allowing for growth of new material
• Induces the formation of tillers by plant hormones
• Helps disperse seeds

Negative Impacts

• Reduces the photosynthetic capacity of the plant by decreasing leaf area
• Decreased photosynthesis can lead to diminished root growth; adequate root growth is essential for plant post-grazing recovery
• Decreases seed production

The rangeland ecosystem can be quite fragile. Invasive plants, or weeds, exert considerable detrimental pressures on this ecosystem. They compete for valuable and scarce resources, are largely unpalatable for grazing, and decrease biodiversity. In addition, they seem to have a unique ability to capitalize on deteriorated land conditions. This is one of the many reasons that it is crucial to maintain the integrity of rangeland resources.

 

 

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