@mastersthesis {51471, title = {Response potential of three perennial desert grasses to various disturbances}, year = {1993}, note = {//NMSU//NONE, LTER//}, month = {1993}, pages = {94}, school = {New Mexico State University}, type = {M.S. Thesispp}, address = {Las Cruces, New Mexico}, abstract = { 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{\textquoteright}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.}, 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}, author = {Beres, Lisa Ann} } @article {51488, title = {Effect of water and nitrogen additions on free-living nitrogen fixer populations in desert grass root zones}, journal = {Applied and Environmental Microbiology}, volume = {59}, number = {9}, year = {1993}, note = {//NMSU//LTER II//Listed in LTER3 proposal as citing LTER2 support//}, month = {1993}, pages = {3021-3026}, abstract = {

In this study we measured changes in population levels of free-living N2-fixing bacteria in the root zones of potted Bouteloua eriopoda and Sporobolus fexuosus plants as well as the photosynthetic indices of the plants in response to added nitrogen, added water, and added water plus nitrogen treatments. In addition, N2 fixer population changes in response to added carbon source and nitrogen were measured in plant-free soil columns. There were significant increases in the numbers of N2 fixers associated with both plant species in the water and the water plus nitrogen treatments. Both treatments increase the photosynthetic index, suggesting that plant exudates were driving N2 fixer population changes. Population increases were greatest in the water plus nitrogen treatments, indicating that added nitrogen was synergistic with added water and suggesting that nitrogen addition spared bacteria the metabolic cost of N2 fixation, allowing greater reproduction. Plant-free column studies demonstrated a synergistic carbon-nitrogen effect when carbon levels were limiting (low malate addition) but not when carbon was abundant (high malate), further supporting this hypothesis. The results of this study indicate the presence of N2 fixer populations which interact with plants and which may play a role in the nitrogen balance of desert grasslands.

}, keywords = {article, articles, bacteria, Bouteloua, bacteria, nitrogen fixers, bacteria, Sporobolus, Bouteloua, N2 fixing bacteria, Bouteloua, photosynthesis, Bouteloua, soil nutrients, grass, Sporobolus, grasslands, soil bacteria, journal, journals, Sporobolus, N2 fixing bacteria, Sporobolus, photosynthesis, Sporobolus, soil nutrients}, url = {files/bibliography/JRN00169.pdf}, author = {Peter Herman and Kerri R. Provencio and Ruben Torrez and Seager, Gwen M.} } @mastersthesis {52118, title = {Phenological development and impact of season and intensity of defoliation on Sporobolus flexuosus and Bouteloua eriopoda}, year = {1980}, note = {//NMSU//NONE//}, month = {1980}, pages = {110}, school = {New Mexico State University}, type = {M.S. Thesispp}, address = {Las Cruces, New Mexico}, abstract = {The objectives of this study were to determine how eight seasonal defoliation patterns affect regrowth of dry matter yield and basal diameter of mesa dropseed (Sporobolus flexuosus [Thrub.] Rhydb.) and black grama (Bouteloua eriopoda [Torr.] Torr.); determine how these defoliation patterns affect the reproductive potential of black grama; quantify seasonal phenological stages of growth in both species; and interpret the data in terms of management application. Regrowth and basal diameter of both species clipped to remove 30 percent the first year during vegetative growth had increased after two growing seasons. Therefore, for continued forage production, light use prior to floral development is recommended. Regrowth, basal diameter, and stolon numbers increased over two growing seasons in black grama plants clipped to simulate light use at dormancy. Therefore, light use of black grama during the winter is encouraged.}, keywords = {Bouteloua, defoliation, Bouteloua,management, Bouteloua,phenology, cattle grazing, Bouteloua, cattle grazing, Sporobolus, dissertation, dissertations, grass, Bouteloua, grass, Sporobolus, grassland, management, grassland, reproduction, productivity,grassland, Sporobolus, defoliation, Sporobolus,management, Sporobolus,phenology, theses, thesis}, author = {Young, Steve A.} } @proceedings {52143, title = {A grazing system for semiarid lands}, volume = {Vol. 1}, year = {1978}, note = {//NMSU//NONE//ProCite field[6]: In}, month = {1978}, publisher = {Society of Range Management}, abstract = {A seasonal suitability grazing system was started on semiarid grassland in 1967. Ten years of data have not shown it to be superior to yearlong grazing with which it was compared. Livestock performance was similar on the two systems. Drought and conservative stocking rates were primarily responsible for the lack of differences between the systems. Flexibility, a primary component of the seasonal suitability system, allows for specific management of perennial grasses. Sampling of vegetaion was not intensive enough to detect the observable improvement on the seasonal suitability pastures.}, keywords = {abstract, abstracts, cattle grazing,management, conference, conference proceedings, conferences, grass, Aristida, grass, Bouteloua, grass, Erioneuron, grass, Sporobolus, grassland, grazing system, grazing system, management,grazing system, proceeding, proceedings, shrub, Xanthocephalum, snakeweed, SEE Xanthocephalum, Gutierrezia}, author = {Reldon F. Beck}, editor = {D. H. (ed.) Hyder} }