Greener Roadsides

Drought Affects Desert Too

In spite of adaptations, deserts also suffer under drought conditions.

The desert grassland, a naturally arid plant community, found in Arizona, New Mexico and Texas also was impacted by the dustbowl days. The grassland is shaped by low rainfall, warm temperatures and high solar radiation. Evapotranspiration (soil evaporation and plant transpiration) is regularly two to three times greater than the rainfall. A mosaic of grassland and desert scrub tolerates this environment under normal conditions.

In spite of this community's adaptation, add the stress of drought as occurred in the late 1800's and drastic change followed - enough change to stir interest in revegetation of desert grasslands.

"Although the drought was the precipitating factor, early researchers placed the blame for the decline of perennial grasses squarely on overgrazing, which weakened grass root systems, making them unable to withstand drought, set seed for regeneration or recover when precipitation finally arrived." Revegetation with native forage grasses was begun near Tucson, Arizona in 1907.

As decline during drought occurred, invasive plants, many of which were unpalatable by cattle, increased on this landscape. The undisturbed native grasses and forbs were credited with having deterred the invasion before the drought. With grasses and forbs decreasing, the mesquite tree was substituted for stock feed The mesquite then invaded former grasslands. By the 30's its control was begun. Because of these invasions in grasslands, research management with fire began in the 1950's. We learned that this somewhat stable grassland could not withstand grazing and drought pressure all at the same time.

(McClaran and Van Devender, 1995)