Browsing by Subject "Plant ecology"
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Item Comparative Anatomy of the Leaves of Yucca Campestris Mckelvey(Texas Tech University, 1969-08) Eagan, Anthony RolandNot Available.Item Comparative anatomy of Xerophytic leaves(Texas Tech University, 1969-08) Gary, Michael HarrisonNot availableItem Competition among blue grama and buffalograss ecotypes: effects of soil and past neighbor interactions(Texas Tech University, 2003-08) Moffet, Corey AllenNative plants are adapted to their environment. Typically, the abiotic component of the environment is given the greatest attention in rangeland revegetation projects. Past research has suggested that selection of plants for fitness to their biotic environment may deserve increased attention. The hypothesis that biotic adaptation is an important component of increased fitness suggests that, for example, sympatric buffalograss should be better fit (have greater productivity and fecundity) to grow in blue grama neighborhoods (especially sympatric blue grama) than allopatric buffalograss populations. The objectives of this study were to: (1) explore the relationships among plant responses and the abiotic and biotic components of the environment, and (2) determine if blue grama or buffalograss have evolved genetically-based adaptations specific to their biotic, abiotic, or combined biotic and abiotic environment. Two populations of buffalograss and two of blue grama were studied; populations included allopatric individuals (e.g., buffalograss plants collected from areas without blue grama) and sympatric individuals (e.g., buffalograss plants collected from areas with blue grama). Ramets of the 4 populations were collected and transplanted into rephcates of 5 different neighborhoods. The neighborhoods included no neighbors, allopatric blue grama, sympatric blue grama, allopatric buffalograss, and sympatric buffalograss. The sites from which these populations were sampled were characterized in terms of soil and vegetation properties. Growth and fecundity responses of these populations were measured; soil water content and temperature patterns were described. Results show that sympatric and allopatric populations responded the same to each of the neighborhood treatments; there were no central population-neighbor population interactions. Likewise, there was no suggestion that populations were more adapted to their site of origin than to other sites. Intraspecific competition was often greater than interspecific competition, although usually they were similar. Site had a significant effect on growth and fecundity for both species. Buffalograss and blue grama respond to their environment, but there are apparently no adaptations in these populations that make them better fit to their site or neighborhood of origin.Item Fire effects on small mammals and vegetation of the Northern Chihuahuan Desert(Texas Tech University, 1997-12) Monasmith, Tony JohnThe role of fire in the Northern Chihuahuan Desen has been of great interest and also heavily debated for 40 years. However, few replicated studies have documented the changes brought about by fire. .My study documented the short term effects of fire on a creosotebush (Larrea tridentata) dominated community and associated small mammal community. Prescribed burns were ignited during 13-15 June 1995 on 10 pairs (10 bumed. 10 unbumed) of 25- ha study sites. The 1995 bums reduced shmb (P = '» 006) and grass (P < 0.000) canopy cover to 64 and 16% of the preburn cover, respectively Complete recovery' of the canopy cover had not taken place 1 year post bum Densities of shrubs, primarily creosotebush. tarbush (Flourencia cemua). and cacti species (Opuntia) were reduced 1 year post bum. Mortality of creosotebush (25.6%) was lower than previously reported for summer burns. Tarbush monality (26 3°o) was similar to creosotebush on the study sites. Above average precipitation during June and July 1996 and lower competition by shmbs for available resources promoted an 1160% increase in forb canopy cover on the bumed sites.Item Influence of varying replacement of potential evapotranspiration on water use efficiency and nutritive value of three Old World bluestems (Bothriochloa spp.)(Texas Tech University, 2004-05) Philipp, DirkForage systems offer alternatives to traditional cropping systems in the Texas High Plains, but information on water management is lacking. This research investigated whether differences in water use efficiency (WUE; kg total seasonal dry matter [DM] yield ha"' mm"' water [precipitation, irrigation, and soil water depletion]) existed among species of old world bluestems (Bothriochloa spp.). Additionally, effects of irrigation amounts on forage nutritive value and plant morphology were explored. Established stands of three Bothriochloa species ('Dahl' [bladhii]; 'Caucasian' [caucasica]; and 'Spar' [ischaemum]) were surface drip-irrigated weekly during the growing season to replace: 1) 0% (dryland); 2) 33% (low); 3) 66% (medium); and 4) 100% (high) of potential evapotranspiration minus precipitation during 2001,2002, and 2003. Soil organic carbon as influenced by irrigation level and optimum metabolic temperature for growth were investigated in 2003. Each species and water treatment was replicated three times in a complete randomized block design with a split plot treatment arrangement. In 2001 and 2002, no differences in water use efficiencies among species were found. Averaged across these 2 yr, WUE of 19.0, 19.3, and 15.3 kg ha"' mm"' were observed for Caucasian, Dahl, and Spar, respectively. In 2003, Caucasian produced 16.9 kg ha" mm', differing (P < 0.05) in slope fi-om Spar (7.4 kg ha"' mm"') but Dahl (12.4 kg ha"' mm"') was not different in slope from either Caucasian or Spar. Maximum seasonal DM yield was obtained with Caucasian under high irrigation (18.0 Mg ha"') vs. Dahl (15.2 Mg ha") and Spar (12.55 Mg ha"') averaged over all years. Percentage dry matter digestibility (DMD) was higher (P < 0.05) in all forage species irrigated at a low level (58% DMD) than for other water treatments (57, 56, and 55% DMD for dryland, medium, and high irrigation, respectively). Dahl generally averaged higher (P < 0.05) percentage crude protein (CP) than other species during the growing season. More differences in percentage CP were observed between dryland and irrigated forages than within the irrigated treatments but CP would have met nutritional needs of most livestock only in May. In all species, percentages total nonstructural carbohydrates (TNC) and DMD and leaf: stem ratio declined while percentage cell wall increased with increased irrigation amount in the first half of the growing season. Effects of irrigation on cell wall, TNC, and DMD appeared related to changes in plant morphology (leaf:stem) and to an increase in physiological age as indicated by growth stage (mean stage count and mean stage weight). Leaf:stem ratio following hay harvest in July showed fewer effects of irrigation treatments but ratios of live:dead plant material generally increased during the growing season in response to increased irrigation (linear effects; P < 0.05). Soil organic carbon was higher (P < 0.05) in all irrigated soils (5.5 g 100 g"') compared with dryland (4.6 g 100 g"') but did not differ among irrigation treatments. Optimum metabolic temperatures for growth of Caucasian, Spar, and Dahl old world bluestems were 24, 24, and 28°C, respectively. Our data suggest that differences in WUE among Bothriochloa species can be identified, and that yield, chemical composition, and morphology can be manipulated through irrigation management to optimize total nutrient yield and nutritive value.Item Root Development of Two Native Grasses using Radiophosphorous and Soil-Block Techniques(Texas Tech University, 1965-05) Pettit, Russell DeanNot Available.Item Vascular flora of the Concho Bluff ecotone(Texas Tech University, 1966-08) Collins, Lawrence TurnerNot available