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Storage and germination of Quercus emoryi and Quercus arizonica acornsNyandiga, Charles Onyango, 1962- January 1991 (has links)
Quercus emoryi Torr. (emory oak) and Quercus arizonica Sarg. (Arizona white oak) are the dominant tree species in many of the oak savannas and woodlands of Arizona and northern Mexico. Objectives of this study were (1) to evaluate germinability on two media as influenced by storage and stratification, and (2) to determine effects of oak canopy and depth of burial on acorn viability and germination. Germination was higher (P < 0.05) on filter paper than in mineral soil in laboratory trials. Maximum germination of Quercus emoryi in the field was observed at 7.5 cm (29%), with only 5% germination at the soil surface. Germination of Quercus arizonica at 7.5 cm (73%) and 15 cm (74%) were not different (P > 0.05) but exceeded germination at the surface (17%). These results are applicable for propagation of the two species in a tree nursery.
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Performance of annual medics (Medicago spp.) as limited by moisture availability and grass competition in southern ArizonaBrahim, Kebe, 1953- January 1991 (has links)
I investigated whether rapid-maturing medics (genus Medicago) could establish and produce seed under the relatively dry winter conditions of southern Arizona. Hardseededness is common in many medics and may limit germination before fall rains. Therefore, I was also interested in the amount of medic germination that occurred following summer rainfall. Five accessions from four Medicago species (laciniata, polymorpha, truncatula and littoralis) were sown with or without a companion grass (Oryzopsis hymenoides) and grown with or without weekly 2 cm irrigation. While single-plant forage yields were over 8 times higher with irrigation, each accession established and produced up to 14 seeds for every seed sown under rainfed conditions. The companion grass had no influence on medic performance. Natural reestablishment occurred in all accessions from pods. Seedlings established in summer did not survive to flowering. M. littoralis appeared particularly well adapted to establishment under rainfed conditions in this environment. (Abstract shortened with permission of author.)
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Anthropology, sustainability and the case of Mexico's sea turtlesPiper, Jessie Celeste, 1950- January 1992 (has links)
Mexico was formerly an important breeding ground for six marine turtle species. Over the last several decades, overexploitation of turtles for their meat, eggs, and hides, as well as habitat destruction, has led to alarming rates of decline in all species. The problem of sea turtle conservation is a promising area for questions of anthropology and sustainable human systems because decline of these species is related to unsustainable development and subsistence practices that have disenfranchised small coastal fishing cooperatives. Common property resource theory aids the analysis of the context in which overexploitation takes place. Conserving sea turtles will depend on the development of localized institutions for managing natural resources in perpetuity and for negotiating the array of regional, national, and global factors relevant to sea turtle endangerment and preservation. Anthropology can play a vital role in this process of developing sustainable interactions between human subsistence needs and natural resource conservation.
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The East African Institute of Resource Planning and Management: A proposalNuwamanya-Matsiko, John Willis, 1950- January 1992 (has links)
East Africa, a region in Africa south of the Sahara, is faced with many environmental and urban problems due to development and population growth impacting on the land, vegetation and wildlife. This region, at present, does not have its own trained manpower able to plan and manage the natural resources but also to minimize man's impact on these resources in order to achieve sustainable development in the region. The thesis of this study is that a regional institute of resource planning and management be established in one of the three countries in the region to meet this pressing need.
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A morphometric analysis of populations of yellow-eyed junco (Junco phaeonotus) in southeastern ArizonaWhite, Jeffrey Lloyd, 1952- January 1992 (has links)
I sampled populations of Yellow-eyed Junco from six mountain ranges in southeastern Arizona to test hypotheses about morphological variation in the species. Morphometric variables were obtained from measurements in the field, and from photographic images of the head, wing, and tail. Statistical analyses revealed significant seasonal differences in values of bill-length variables, and sexual dimorphism in wing and tail characters, but not in bill characters. Statistically significant geographic discrimination among samples was found only for bill characters. Mahalanobis' distance values from subsets of bill and tailspot variables correlate most significantly with geographic distances between habitats measured along an arc of higher elevation in the region. These correlations, the lack of significant geographic discrimination for wing and tail characters, and the many extralimital records for the species imply that Yellow-eyed Juncos move between isolated populations, and that this movement tends to follow higher elevations in the region.
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Physical and chemical soil properties affecting the growth habits of agave speciesHara, Yuto, 1959- January 1992 (has links)
Nine physically and chemically different soil samples from five study sites in which agaves grew, or were grown, were investigated to evaluate the effects of soil physical and chemical properties on the growth habits of agaves. In five Arizona study sites, biomass data of seven agave species has been recorded for the past ten years. Agaves were grown experimentally in the greenhouse using two widely different soil types from the five sites to evaluate growth under controlled conditions. Influence of edaphic factors on agave growth for the study sites and greenhouse experiment was evaluated. The results show that the determinant primary factors were water availability and temperature. Soil texture, soil pH, soil CO2 concentration, nitrogen, and soluble salt concentration were placed as influential secondary factors for the growth of agave. The degree of influence of these soil factors depends highly upon the genetic characteristics of agave species.
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A system for the experimental study of emigration in house miceNelson, Anthony Richard, 1964- January 1992 (has links)
I designed and tested experimental enclosures with 1-way exits for the study of emigration in house mice. Rapid emigration from barren enclosures supported the contention that all mice can find and use the exits if conditions in the enclosures are unsuitable for them. Invariable residency in resource-rich enclosures during the spring, summer and fall revealed that resident animals will not cross the exits during routine behaviors. The enclosures and exits permitted normal emigratory and residency behavior. In experiments on the role of emigration in population regulation, the number of resident mice was consistent in enclosures with fixed levels of resources. The number of residents was about double in enclosures with twice the resources. The first male and few females added in each trial usually became resident, and mice added subsequently usually emigrated. My data suggest that mice were regulating their numbers to available resources through spacing and emigration.
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Corbicula fluminea as a bioindicator on the lower Colorado RiverBell-McCaulou, Teresa Margaret, 1954- January 1993 (has links)
I determined that Corbicula fluminea can be used as a bioindicator on the lower Colorado River. I analyzed tissue samples for trace element concentrations. Selenium and arsenic were elevated above U.S. background levels at 89% and 83% (respectively), of the sites. Selenium concentrations were significantly higher in backwaters than at river sites. Selenium in clams predicts the contamination state of a site 78% of the time. There is a strong correlation between selenium concentrations in clams and selenium concentrations in vascular aquatic plants (r²) and carnivorous birds (r²). The white morph of C. fluminea is more prevalent at northern and backwater sites than the purple morph. Selenium levels in clams at several sites exceeded levels that have been shown to result in teratogenicity for birds in laboratory studies. Birds that eat clams in the study area could have increased risk of lowered reproductive success.
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Germination requirements of Arizona native perennial grasses and their establishment in existing stands of Eragrostis lehmanniana NeesBiedenbender, Sharon Helen, 1950- January 1994 (has links)
Germination of 10 native and exotic grasses was compared for temperature regimes representing abruptly and gradually fluctuating minimum and maximum wet seedbed temperatures in summer, spring, and winter, respectively, in the desert grassland. Gradually fluctuating temperatures produced similar total percent germination but more rapid germination than abruptly alternating temperatures and constant 25 degrees C. Lehmann lovegrass (Eragrostis lehmanniana) and 7 native grasses were sown into stands of Lehmann lovegrass that were left intact, burned, sprayed with herbicide and left standing, or sprayed and mowed. In 1992 mow and dead standing treatments reduced Lehmann lovegrass seedling density and improved establishment of cane beardgrass (Bothriochloa barbinodis), Arizona cottontop (Digitaria californica), green sprangletop (Leptochloa dubia), and plains bristlegrass (Setaria leucopila) compared to burn and control treatments. In 1993 the burn treatment reduced mature Lehmann lovegrass and enhanced establishment of sideoats grama (Bouteloua curtipendula), Arizona cottontop, green sprangletop, and plains bristlegrass compared to the other treatments.
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Conservation of "magnocellular" neurons of the dipteran optomotor pathway: Evolutionary and functional implicationsBuschbeck, Elke Karin Ursula, 1967- January 1994 (has links)
In Diptera, small-field retinotopic neurons supply achromatic motion sensitive neurons in the lobula plate, a region thought to control stabilization of yaw, pitch, and roll during flight. If different body shapes, and the flight performance associated with them, place specific demands on the design of control pathways, it might be expected that flies with long bodies and high aerodynamic pitch stability would show specific differences in the organization of such magnocellular achromatic networks. Striking differences emerge in the comparison of 9 species. Tipulids and culicids possess small non-stratified lobula plates, containing only 2-3 large diameter neurons. In syrphids, all VS cells have wide diameters and overlapping fields covering 2-3 times more of the mosaic than those of calliphorids. In asilids (robber flies) vertical cells cannot be identified. Despite these differences, we observe a conserved relationship between terminals of lamina afferents with neurons in the medulla.
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