• 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.
    • The Woody Vegetation of Eastern Senegal

      Dickie, A.; Pieper, R. D.; Dickey, J. R. (Society for Range Management, 1987-01-01)
      The woody component of the vegetation of eastern Senegal was sampled using the point-centered quarter method. Data were evaluated using cluster, principal component, and multiple discriminant analysis (MDA) techniques. Sites were grouped into 8 ecologically significant groups. Six of these groups were considered woodland lateritic sites, and 2 drainage sediment sites. Species of the genus Combretum dominated all sites. The effect of livestock grazing on the botanical composition was inferred through the use of 4 environmental variables as discriminant factors in MDA. A floristic record of species composition and guidelines for management are embodied in the results of the analyses.