• An Evaluation of Range Condition on One Range Site in the Andes of Central Peru

      Wilcox, B. P.; Bryant, F. C.; Fraga, V. B. (Society for Range Management, 1987-01-01)
      Little published information is available on the vegetation or its response to grazing in the high elevation (3,900-4,800m) grasslands of the Andes, known as the puna. The objective of this study was to evaluate grazing-induced vegetation changes on a major range site in the puna. Basal cover and diversity were compared on (1) rangelands managed by a cooperative of land holders (moderate grazing); (2) communal grazing land (heavy grazing); and (3) sacrifice or holding pastures (very heavy grazing). Basal cover was determined using point transects. With increased grazing pressure standing height of the vegetation was greatly reduced as was vegetation basal cover. Total cover of grasses was reduced while forb cover increased. Ability of a species to grow close to the soil surface probably enabled it to tolerate very heavy grazing. Species diversity as determined by Simpson's D, Shannon-Weaver's H', and species richness was highest on the community lands.
    • C3/C4 Production Shift on Seasonal Burns: Northern Mixed Prairie

      Steuter, A. A. (Society for Range Management, 1987-01-01)
      This study investigates the potential of fire to manipulate the balance of C3 (cool-season) and C4 (warm-season) herbage in 2 northern Mixed Prairie communities. The xeric high prairie community and mesic low prairie community were chosen to represent regional moisture extremes. Treatments included dormant spring burn, mid-summer burn, dormant fall burn, and untreated. The high prairie community appears to be a C3-dominant type. All 3 burn treatments increased the C3 herbage fraction relative to untreated sites. Total production, however, was unaffected by treatment. The C3/ C4 ratio of high prairie communities appears to be the result of long-term adaptation rather than short-term adjustments to fire or weather effects. Spring burning shifted low prairie communities towards C4 herbage relative to other treatments. This was due to an increase in C4 herbage (and total) rather than to a decrease in C3 herbage. The C3/C4 ratio of low prairie communities did appear to respond to short-term adjustments in moisture, temperature, and light caused by the spring burn. The response of low prairie C3/C4 ratios to mid-summer and dormant fall burns appeared to be related to phenological and indirect weather effects rather than to changes in site microclimate caused by the fires.
    • Relationship of Saltbush Species To Soil Chemical Properties

      Hodgkinson, H. S. (Society for Range Management, 1987-01-01)
      The relationship of pure stands of 6 saltbush species to sodium adsorption ratio, electrical conductivity, and alkalinity are documented. The data gathered were obtained while correlating soils to range sites for National Cooperative Soil Surveys. Soil scientists gathered detailed soil information and obtained lab data. Range conservationists correlated the saltbush species to specific soils and by using lab data made a direct relationship to pure saltbush stands. Species ranked from highest to lowest adaptability to SAR, EC, and pH are: mat saltbush (Atriplex corrugata S. Wats.), mound saltbush (A. obovata Moq.), Castle Valley clover (A. cuneata A. Nels.), sickle saltbush (A. falcata (M.E. Jones) Standl.), shadscale (A. confertifolia (Torr. & Frem.) S. Wats.) and fourwing saltbush (A. canescens (Pursh) Nutt.). By knowing the SAR, EC, and pH tolerances of these 6 species, interpretations for inventorying, rating plant community potentials, and applying range improvements will be achieved with greater success.
    • Succession of Pinyon-Juniper Communities After Mechanical Disturbance in Southcentral New Mexico

      Schott, M. R.; Pieper, R. D. (Society for Range Management, 1987-01-01)
      Principal component analysis (PCA) was used to interpret secondary succession of pinyon-juniper stands after cabling or bulldozing. Soil types were used to separate 93 sample units into 3 groupings. A PCA was run on 2 of the groupings. Groups of sample units were defined as community types for each ordination. Stepwise discriminant analysis using environmental variables was used to assist in delineation of community types. Species that contributed the most to the first 3 principal components were compared among community types for each ordination using an analysis of variance and a comparison of the least squares means. Grasses on the deeper soils usually increased after cabling, but after 25 years they had declined to near pretreatment levels. Wavyleaf oak (Quercus undulata Torr.) increased after cabling, and on the older cablings it had reached higher cover values than on the other community types. Pinyon and juniper response appeared to be dependent on density and size of trees before cabling. If the stand was near climax before cabling, pinyons rapidly became dominant on the site. If it was seral, there would be more junipers, but their slow growth and the time they require for maturation required more time before they dominated the site. The successional pattern following cabling on relatively deep soils is similar to what was found after fire, but it occurs faster. Cover of grasses and shrubs increased more on rock-free soils compared to sites treated similarly but with rock. The ordinations indicated that succession in pinyon-juniper communities is directional and leads towards climax with a decrease in variability among sites.