by Reuben G. Wagelie, M.D.
The Physical Geography of Southeastern Arizona’s basin and range consists of wide valleys and mountains ranging from 3,000 to 10,000 feet in elevation. The soil varies from deep fine-textured to rocky shallow soils in the mountains. Precipitation varies from 10 to 35 inches per year. These factors, for the most part, determine the quality and the quantity of the vegetation.
The major communities in this area include Benson, Sonoita, Patagonia, Sierra Vista, Nogales, Bisbee, Douglas, Willcox, Safford, and the Clifton-Morenci area. A pollen survey conducted by the Environmental Sciences Services Administration in Fort Huachuca identified the predominant allergens.
Pollens from trees dominate the spring months. In high elevations, mountain cedar, cottonwood, and junipers pollinate as early as January, followed by other trees indigenous to the area. This includes mulberry, ash, elm, mesquite, and walnut and oak at higher elevations. Water-dependent trees such as sycamore and cottonwood are found in the arroyos. Cottonwoods are the dominant trees along the banks of the San Pedro River. The pecan groves along the Santa Cruz River, not only in the Southeastern Basin but also in the Central Arizona Basin, contribute to the spring problems.
Bermuda is the dominant grass. It is equally important in the higher elevations as it is in the Central Basin.
The desert grassland areas are on the rolling and hilly outwash slopes at elevations from 3,000 to 5,000 feet. Grama grass, Lehman’s love grass, and sprangletop grass were identified. While these grasses pollinate in late spring and summer, Bermuda and Johnson continue through fall.
Giant ragweed (ambrosia), familiar to those who used to reside in the East or the Midwest, in not common. Other weeds, some referred to as false ragweeds, are found, including rabbitbush, slender ragweed, bursage, careless weed, saltbush, and tumbleweed.
The pollen and mold survey also indicated the presence of molds almost through the year. The Willcox and the Thatcher-Safford areas are basically ranching and agricultural communities. Molds commonly isolated were Alternaria, Cladosporium, and Helminthosporium.
Posted in: Allergens