In the Southwestern United States, desert grasslands are some of the rarest ecosystems, as well as some of the richest in biodiversity, according to Nature Conservancy.
In southeastern Arizona, desert grasslands support a variety of endemic plants and animals including tanglehead grass, the Sonoran green toad, termites, and antelope.
George Montgomery, Curator of Botany at the Arizona-Sonoran Desert Museum, said unlike the Tallgrass prairie of the Midwest, desert grasslands are home to a large variety of herbaceous plants and woody plants, such as acacias, mesquites, yucca, and ocotillo.
Photo: AZPM Staff
In order to co-exist alongside grasses, woody plants must be located where they can tolerate fire, because desert grasslands are adapted to fire. Grasses need the oldest part of the plant at the tip -the thatch- removed to allow sunlight to the base -the crown- so new growth can form. Fire burns off the thatch, and the burned plants restore nutrients in the ground.
This recycling of nutrients is beneficial to the soils and to the roots of plants. Organic material is slow to decompose in arid environments without the aid of fire, termites, or grazing. If all fire is controlled, Montgomery said "eventually there can be a die out".
Threats to grasslands come in the form of urbanization, expansion of agriculture, and the invasion of exotic species.
The Nature Conservancy said that 31 percent of the state’s former grasslands are in good condition with native perennial grasses and low shrub cover, while 34 percent are shrub-invaded but have the potential to be restored. The remaining areas have transitioned to shrub land or exotic species of grass. Montgomery said, in Southeastern Arizona, "it could be 40 percent of the square mileage is grasslands".
"Rolling hills, with the scattered oak trees..." Montgomery said. "It's just exciting to travel through the quadrant of the state."