|Title||Response potential of three perennial desert grasses to various disturbances|
|Year of Publication||1993|
|Number of Pages||94|
|University||New Mexico State University|
|City||Las Cruces, New Mexico|
|Thesis Type||M.S. Thesispp|
|Keywords||Aristida, germination, Aristida, grazing, Bouteloua, germination, Bouteloua, grazing, dissertation, dissertations, germination, grass, germination, Sporobolus, grass, Aristida, grass, grazing, grass, Sporobolus, grass,Bouteloua, grass,germination, grassland, germination, grassland, grazing, Sporobolus,clipping effects, theses, thesis|
Increasing desertification of the northern Chihuahuan semidesert grasslands is linked, in part, with the decline or disappearance of perennial grasses. While vegetational changes have been well documented since the early 1900's, no clear cause for these changes has been determined. Although many disturbances have been linked to these changes, this study focuses only on grazing, microsite, and competition effects. By measuring the growth potential, establishment potential, and germination rates of Bouteloua eriopoda, and Sporobolus flexuosus, and Aristida wrightii, the study provided insights into potential response to these disturbances. In these dominant perennial grasses, grazing effects were measured in three major ways. A descriptive survey assessed differences between plants and populations with a history of livestock grazing and those without. Secondly, a clipping experiment measured regrowth potential in response to biomass removal from selected plants within these areas. Finally, differences in clonal spread in Bouteloua eriopoda were measured in grazed and ungrazed locations. In all three species, microsite effects were assessed through the survivorship and growth of clonal transplants planted into open and vegetated patches within shrubland and grassland communities. For competition effects, survivorship and growth responses were measured for the three species growing together in pots that were either in full sunlight or shade. In these studies, growth and establishment potential was measured by assessing plant height, plant size, stolon length, number of tillers or stolons, number of nodes, and flowering seed production. Germination rates were determined in a lab study, using seeds of the three grass species. Results indicated there were some significant grazing effects for the variables studied in some of the species. However, there was no significant effect of grazing history on response to clipping for any of the study species. Clonal spread was significantly different between sites and treatments in Bouteloua eriopoda. Survivorship was low for the clonal transplants. However, two of the three grass species had a higher survivorship within the vegetated microsite patches. In contrast, in the greenhouse experiment, the transplants that were in full sunlight had more tillers and increased height than those in the shade. Aristida wrightii had the highest seed production and germination rate.