Call number: LD2668 .T4 1952 T3 / Master of Science

The ecology of netleaf hackberry (Celtis reticulata Torr.) is poorly known throughout its broad western range. To gain some understanding of the species' basic ecology, three components of its life history were studied. First, seed germination requirements were analyzed under laboratory conditions. Second, hackberry population dynamics were evaluated from tree size and age structures. Lastly, an examination of hackberry's response to fire was made, using tree-level post-fire data. A higher percentage of non-stratified hackberry seed germinates if the seed is mechanically scarified. While germination percent is low, the treatment may eliminate the 120-day stratification period recommended by some authorities. Even with cold stratification, germination is usually quite low for Celtis species. Fermenting fruits for 72 hours and subsequent depulping prior to scarification did not significantly increase germination levels, as hypothesized. However, seed that was not scarified but was fermented with its pulp intact germinated at a higher rate than the non-fermented, non-scarified seed. This result may be significant to its biology. Seed is typically cleaned prior to planting by seed distributors. However, hackberry seed with its pulp retained may in fact have a superior germination rate, as it is allowed to undergo natural processes of fermentation resulting from moist field conditions. In Idaho, hackberry's uniquely fragmented distribution appears to be controlled by a variety of factors. Hackberry is generally restricted to semi-arid portions of the state where temperatures are least severe during the winter months, such as in moderated river canyons, or at elevations below 1600 m. It occurs in a variety of habitats, from riparian to upland, however it is most abundant on sites with a southeast-to southwesterly aspect and a rocky surface cover. The presence of rock below the surface may be equally important, but this factor was not quantified. Hackberry is a slow-growing species in Idaho, averaging 3.9 m tall at 50 years. Differences in hackberry growth rate under a variety of site conditions were evaluated by a site index constructed from the log-log regression of height on age. Trees reach maximum heights where topographic shelter is greatest, such as in draws, and where soils are loamy. However, well-drained soils may be important, as nearly all soils had some sand or skeletal component. Hackberry can be long-lived, with the maximum age recorded at 374 years; the average age was 66 years (N = 959 trees). Hackberry appears to be reproducing, in spite of habitat degradation caused by livestock overgrazing, alien plant invasion, and increasing fire frequencies. However, newly established even-aged stands are rare and are generally found along waterways on stream terraces or at high water lines. In these areas, surface rock cover was typically high, with the rock providing a moderated below-ground microclimate, as well as protection from herbivores. Recruitment is favored by rockiness at the surface, but growth rates of established individuals are not higher with more surface rock. Under severe livestock grazing pressure, stands had a single dominant cohort and lowered recruitment. Fire-caused mortality of hackberry growing in low density stands appears to be uncommon in Idaho. In nine burns, only 8% of the trees (N = 161) were dead after the fires. This mortality, however, cannot be attributed solely to fire, as pre-burn vigor was not evaluated. Individuals typically persist or resprout following fire. Mortality rates were highest for individuals with a high percent cover of live vegetation below their canopy. Temperatures were probably more intense within the live vegetation, where the fire could feasibly linger long enough to kill the roots of the associated hackberry. While burns in high density stands were not observed, these burns could result in greater mortality, due to their greater continuity of plant cover. / Graduation date: 1993

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

archives@tulane.edu / The Hackberry Ramblers are best known as an historic southwest Louisiana band that pioneered the synthesis of Cajun music with various English-language genres, especially country music, and also as a group which pioneered the performance of this blend via the then-new technology of electronic amplification. These innovations had profound effects upon the evolution of Cajun music, and exerted a significant degree of influence on country music, too. But closer consideration of the Hackberry Ramblers’ entire oeuvre reveals that the band’s eclecticism far surpassed the presumed limits of its Cajun/country dual identity. During the Ramblers’ seventy-five years in existence, much of the group’s repertoire did consist of Cajun material, both archaic and contemporary, along with old-time country music, the country-jazz hybrid known as western swing, and mid-century honky-tonk country. In addition, however, at various times, the Hackberry Ramblers delved into traditional jazz; nineteenth-century parlor music; popular songs and vaudeville material; blues; rhythm & blues (henceforth referred to here as R&B;) swamp-pop; the occasional zydeco song; 1950s rock à la Chuck Berry, and 1950s rockabilly à la Jerry Lee Lewis; and more. Such considerable variety achieved seamless unification due to the band’s dedicated raison d'être of keeping happy couples out on full dancefloors. In addition, at the behest of the RCA-Bluebird record label, to which the Hackberry Ramblers were signed in the 1930s, the band recorded some unlikely and incongruous songs that were not dance-oriented. This thesis examines the Hackberry Ramblers’ recordings, from 1935 through 2004, and how these recordings established the band’s lasting legacy in both Cajun music, and country; the cultural/socio-economic changes that shaped the Ramblers’ continually evolving sound; and the broader musical contexts of the years during which they were active. This writer played with, managed, and produced the band, beginning in 1987, and thus there will be some discussion, both analytical and anecdotal, of those hands-on roles in the band’s late-career phase, and my de facto function as a participant-observer. / 1 / Ben Sandmel

Evapotranspiration rates of plots with vegetative cover and evaporation rates from bare soil differed during the active growing season of desert hackberry (Celtis pallida) plants but total water losses from both plots for the year were the same. Thermally induced vapor flux appeared to contribute insignificantly to moisture movement under the desert hackberry plant. The difference in measured available soil moisture was independent of location from the plant center during the growing season. During the winter months, when the plants were semidormant, soil moisture measurements had more variability and measurement locations appeared to be important due to differential rainfall input. The determined soil moisture release curve and soil water conductivity values (using an in situ technique) appeared to be representative of the conditions at the study site. A model using soil and plant parameters predicted evapotranspiration rates during the active growing season of the plants when water was not a limiting factor. Calculated results using the model were unreliable when plants were under stress -- very low soil water content. Monitoring of climatic parameters delineated only major differences in surface albedo and net radiation between plant cover and bare ground. Potential evapotranspiration estimations were high but within acceptable bounds for desert conditions. Plant diffusion resistance for the desert hackberry plant, determined from a climatological model and measured soil moisture changes, appeared to increase linearly with decreasing soil moisture until it reached a critical value, below which it rose sharply.

Previous research has shown that polyembryony occurs in many species of the Ulmaceae. The purpose of this study was to determine the method of multiple embryo formation in netleaf hackberry, Celtis reticulata Torr. Collections of specimens were made throughout a two-year period. Collections were begun in early spring while the trees were still in the bud state. Collections were continued regularly throughout the growing season. The collections were preserved in FAA solution and were prepared for microscopic examination as follows: (1) The tertiary butyl paraffin method was used for dehydrating and embedding. (2) Sectioning was done on a rotary microtome at 7-20 microns. (3) Staining of the slides was accomplished by Conant's Quadruple. Examination of the slides reveals at least two, and possibly four, ways by which polyembryony may occur in C. reticulata. The most frequent method of multiple embryo development appears to be the development of an extra egg-like cell--probably a synergid--in the embryo, sac. Some slides show the egg-like cell after it has begun to develop into an embryo. The splitting of the zygotic embryo was observed on the slides and supported by germination studies in which double epicotyls were found on a single hypocotyl. Suspensor budding appears to be a means of multiple embryo formation, but the possibility of faulty interpreation of the sections, due to the plane in which they were cut, could discount this theory. Nucellar budding is also a possible means of multiple embryo development. However, here again the possibility exists that faulty sectioning of the material occurred. While the slides appear to show embryos being formed along the nucellar layer, these embryos could be of synergid origin. If nucellar budding does actually occur, it would have great genetic and evolutionary significance. Seed germination studies reveal a high percentage (20%) of multiple seedlings. It is also noted that frequently a seed will abort a few weeks after pollination. The reason for this abortion is unknown, but the author speculates that this is due to embryo degeneration. The possibility of a growth-stimulating substance being injected into the plant by the Psyllid which parasitizes C. reticulata is, the author believes, a plausible theory worthy of further study.

Thesis (D. Min.)--Gordon-Conwell Theological Seminary, Charlotte, NC, 2000. / Abstract and vita. Includes bibliographical references (leaves 110-114).