Brush control and seeding rangeland

TitleBrush control and seeding rangeland
Publication TypeConference Proceedings
Year of Publication1977
AuthorsHerbel C.H.
Conference NameRange Management Short Course, New Mexico State University, Cooperative Extension Service; Lincoln National Forest, USDA; and Grazing Advisory Board
Date Published1977
Keywordsaverage annual evaporation, average annual precipitation, brush control, drought, research notes, seeding, Southwest
AbstractFor many people, the romance of the Southwest is the favorable climate--winters are warm and dry and summers are relatively dry so the heat is rarely oppressive. For the range manager, the key word in these descriptions is "dry." Over the arid Southwest, the average annual precipitation is 8 to 12 inches. Averages, however, mean very little. Precipitation varies widely from one time to another and from one place to another, only a few miles away. Rainfall from April through September governs the growing season for range forage. West of the Sacramento Mountains about 55 percent of the average annual precipitation falls from July through September; springs are usually dry and windy. East of the Sacramento Mountains growing-season precipitation is more evenly distributed between spring and summer. The average annual evaporation from Weather Bureau pans is about 90 inches--about 10 times as much as the precipitation. The range plants, therefore, grow in brief bursts when soil moisture is available immediately after rainfall. Droughts are frequent and expected. Infrequent wet spells may bring a false sense of security, but chances are that drought, hopefully short but possibly of several years' duration, will follow. Stands of perennial grasses are often severely reduced by drought. On the Jornada Experimental Range near Las Cruces, the basal cover of black grama was reduced to 42 percent of its predrought cover during the 1916-18 drought, 11 percent during the 1921-26 drought, and 23 percent in 1934. During the Great Drought from 1951 to 1956, black grama cover was reduced to 1 to 50 percent of its predrought average, depending on soil type. The drought loss was much more severe on deep sandy sites than on sites with shallower sands. Where 99 percent of the black grama was lost there has been no recovery. Droughts are a fact of life in this region and must be anticipated in the management of any southwestern range. There is no evidence that the climate is getting drier.