Answer: Soil moisture and fertility
Cheat grass is likely to decrease the soil moisture of the region, thus rendering the soil infertile and unfit for other plants growth.
Step-by-step explanation:
Cheatgrass is an exotic weed native to Europe, West Asia and Northern Africa. Cheatgrasses outcompeted native vegetation as a result of large number of livestocks like cattle and sheep into sagebrush region. The livestocks overgrazed on native vegetation, which resulted to a void filled rapidly by Cheatgrass.
Cheatgrass grows on pastures, hills, and ranges. Wildfires promote more Cheatgrass but destroy native plants vegetation. Cheatgrass can survive drought due to deep root system they possess. The deep root system make the plant to grow and flourish with even small amount of water. Its deep root system reduce soil moisture and deplete soil fertility, preventing the growth of other plants. Also, Cheatgrass is self germinating and require les soil to grow. All these attributes that favor Cheatgrass have threatened native plants such as sagebrush plants and woodlands.