No description available.

No description available.

No description available.

No description available.

Thesis (Ph. D. - Renewable Natural Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 165-174).

Thesis (Ph. D.)--York University, 2002. Graduate Programme in Environmental Studies. / Typescript. Includes bibliographical references (leaves 203-222). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ72016.

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Jeffrey C. Mosley. Includes bibliographical references (leaves 525-59).

The use of fire in rangeland has become standard practice for decades; however, there is no shared understanding of how fire affects soil properties. The exact relationship between fire and soil properties is still yet to be understood. The differences in fire frequency, fire intensity, fire severity, the period between fire and sampling resulted in contradictory results amongst studies. A long-term trial at the University of Fort Hare provides a valuable experimental layout for fire research. The trial was established in 1980 with the aim of investigating the effect of burning frequency on vegetation species composition and biomass production. The objective of this study was however to determine the effect of fire management on soil chemical and physical properties under the long-term burning experiment. The treatments of the study site were: no burn (K), annual (B1), biennial (B2), triennial (B3), quadrennial (B4) and sexennial (B6) burns. A line intercept sampling technique was used to collect the soil samples from the surface (0 to 75 mm) for both chemical and physical analysis. All Burning treatments significantly (p < 0.05) increased the bulk density (Db), soil pH, total cations, Magnesium (Mg) and Calcium (Ca), but reduced the soil porosity and exchangeable acidity when compared to the control. Hydraulic conductivity (Ks), water conducting macroporosity (WCM) and total nitrogen were reduced under more frequent burning treatments (B1, B2), as compared to less frequent burning treatments (B3, B4, B6). The aggregate stability showed an opposite trend. Total organic carbon (TOC) was reduced only under annual burning treatment. Burning frequencies did not impact the extractable Phosphorus (p), Potassium (K), Sodium, soil water repellency and water content significantly (P > 0.05). The risk associated with annual burning showed in this study might facilitate processes such as overflow that lead to soil degradation. Triennial burning in rangeland ecosystem supports soil conservation practices. Further studies that measure the quality of rangeland in triennial burning is necessary.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / The Bokkeveld Plateau, a region hosting high plant endemism, is home to two arid mountain centre renosterveld types. One, Nieuwoudtville Shale Renosterveld, has partially been transformed into croplands and pastures, with about 40 % remaining as non-contiguous fragments on privately owned land, and is used as natural rangelands for sheep grazing. The vegetation, soil chemical parameters, and rhizosphere soil microbial ecology of a dominant plant, Eriocephalus purpureus, were assessed. A combination of field sampling and recording, laboratory analyses of soil samples, and interviews were used to glean data. Data were statistically analysed using multivariate techniques. Overall plant species richness did not differ among the study sites, though plant species richness and cover of the different plant growth form categories varied among the sites. Soil chemical parameters varied among sites. Soil chemical and rhizosphere soil microbial parameters co-varied, and showed different profiles among the study sites. High cover of E. purpureus was associated with high microbial enzyme activity, while high cover of (other, non-dominant) non-succulent shrubs was associated with high bacterial functional diversity. Cover of geophytes, Asparagus capensis and perennial grass was associated with high microbial biomass. The findings indicate that E. purpureus-dominated Niewoudtville Shale Renosterveld is heterogeneous not only in terms of vegetation, but also in terms of soil chemical and microbial parameters. The results support the conservation of all fragments of remaining renosterveld, as they may serve as valuable resources of not only plant genetic material but also of soil microbial communities.

This paper will report the results of a study commenced in 1935, at the Desert Experimental Range, Pine Valley, Millard County, Utah, to determine the relative effects of various grazing treatments upon the plant members of the shadscale [Atriplex confertifolia (Torr. And Frem.) S. Wats.] - winterfat [Eurotia lanata (Pursh) Moq.] plant association. Results of this study indicate that distinct vegetational changes have occurred within that plant association during twenty-three years of controlled grazing by sheep.