History of Livestock Use. Procedures Vegetation categories .. Species composition classes. 1858 Survey. 1915 Survey 1928 Survey. 1963 Survey. Vegetation map analysis EXPERIMENTAL RESULTS Vegetation Types Area with no mesquite, tarbush, or creosotebush (O). Mesquite (1).

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. A bstr act. A vegetational survey on the Jornada Experimental Range in southern NewMexico, taken annually from 1941 through 1957, is the basis for a study of the effects of the great drought of 1951 through 1956. Both cover and yields were studied. Observations were stratified into seven classes based on a consideration of landform and soil characteristics. Seasonal and annual precipitation during the drought averaged 55% of the pre-drought average. The most severe drought years were 1951, 1953, and 1956.Both the cover and yield of Bouteloua eriopoda (Torr.) Torr., the dominant species on the upland sandy soils, were greatly reduced by drought. However, drought damage was much more severe on the deep than on shallow sands. When the impermeable caliche layer occurred at shallow depths, moisture relations during drought were apparently much better than when caliche occurred at greater depths.Another result of drought was the invasion of Prosopis juliflora (Sw.) DC. in areas where grass stands have been thinned by drought.Sporobolus spp. and Aristida spp., minor components of the climax, were more susceptible to drought damage than Bouteloua eriopoda.Yields of perennial grasses per unit cover were as great during the drought as prior to the drought. Both winter-spring and summer precipitation are important in preventing death losses of black grama. In arid areas it seems necessary to consider both cover and species composition in arriving at a potential for a site.

Authors are range scientist, USDA-ARS. Jornada Experimental Range; professor and range technician, Animal

In 1939, an experiment was established on the Jornada Experimental Range to evaluate the effects of shrub removal, rabbit exclusion, furrowing, and seeding in creosotebush [Larrea tridentata (DC.) Cov] vegetation. Sixteen plots (21.3×21.3 m) were laid out in four rows of four plots per row with a buffer zone of 7.6 m between plots and rows. A barbed wire fence excluded cattle and poultry wire fencing excluded lagomorphs. Treatments were factorially applied at two levels. Plant cover in the plots was sampled in 1938 (before treatment), 1947, 1956, 1960, 1967 and 1989 with randomly located, line-intercept transects. Data from all sampling dates were analyzed as a split plot in time and main effects for 1989 tested by analysis of variance for a 2×4 factorial experiment. There were significant (P<0.10) year x treatment interactions. Seeding and furrowing treatments were ineffective but lagomorph exclusion and shrub clearing treatments resulted in significant treatment differences for several species. In 1989, basal area of spike dropseed (Sporobolus contractus A.S. Hitchc.) was 30-fold greater on the lagomorph excluded than on the lagomorph unexcluded treatment. Canopy cover of honey mesquite (Prosopis glandulosa Torr. var. glandulosa), tarbush (Flourensia cernua DC.) and mariola (Parthenium incanum H.B.K.) were affected by lagomorph exclusion. None of the responses were viewed as successional in nature. They principally represented individual species sensitivities to either absence of a primary herbivore or removal of aboveground shrub biomass. Though the physical treatments could be regarded as relatively severe disturbances of the system, the impacts on community vegetation dynamics were relatively insignificant.

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