In November of 1984 and 1985, Euphorbia lathyris was planted into a field naturally infested with Macrophomina phaseolina located at the Campbell Avenue Farm in Tucson, Arizona. Plants without foliar symptoms and rhizosphere soil were sampled regularly from emergence until the following May or June. Soil rhizosphere populations ranged from 0.7-3.0 cfu/g soil in 1985 to 8.0-24.1 cfu/g soil in 1986, and did not change significantly over either growing season (P > 0.05). Both the incidence of disease and the number of infection sites per cm of root increased significantly (P < 0.05) over each growing season and were not related to rhizosphere soil populations of M. phaseolina (P > 0.05). The distribution of infection sites along the tap root over both growing seasons remained the same in that most were located in the top 0-7 cm of tap root. Infected E. lathyris without apparent symptoms were subjected to low-water and high-temperature stress treatments in growth chambers. Root infection was not found to be dependent upon any stress. Lesion development was significantly dependent upon the imposition of any stress treatment, and further root colonization was significantly dependent upon low-water stress (P < 0.05). M. phaseolina was consistently recovered from asymptomatic roots. A consistently lower leaf water potential was measured on infected E. lathyris than from non-infected controls when no stress treatment was applied. Polyclonal antisera made against hyphae and microsclerotia of M. phaseolina was not successful in detecting this pathogen in E. lathyris by I-ELISA. Antisera applied to fresh thin sections of infected plant tissue was effective in staining hyphae of M. phaseolina when used with a second antibody conjugated to fluorescence isothiocyanate or to an enzyme (to which a substrate was added to "stain" hyphae).

The tremendous increase of population in Egypt has caused the Egyptian government to rethink its settlement policy by planning for the development of new desert communities in remote arid regions outside of the Nile Valley. Presented here is a methodology for generating appropriate energy design guidelines for desert housing in these new communities. The methodology also takes into account the culture, climate and economy of the country. This interdisciplinary study starts by examining the current government national policy for regional and urban development in Egypt with emphasis on the new desert settlement programs in general and on the Sadat City in particular. The criteria which determines human thermal comfort requirements for the indigenous people of Egypt is then presented. This part of the study also includes a climatic analysis of Egypt showing the major climatic components, the factors modifying the climate, the country's major climatic zones, and microclimatic considerations. In the next chapter on energy analysis, the concepts and the mathematical basis of the methodology are presented. The process is based on balancing the incremental cost/benefit of conservation and passive solar designs in an optimum mix yielding the best performance and economic advantages for any given set of weather characteristics. Finally, the method is generalized and reduced to a set of formulas which generate energy guidelines for conservation levels with selected passive solar system(s). A computer model of the method is developed and energy guidelines for six major locations in Egypt are illustrated. In conclusion, a preliminary design for low-energy cluster houses at the new desert community Sadat City is developed using the computer generated guidelines for that region. The energy results are then validated using the CalPas3 energy simulation program, and a matrix is also developed for assessing the socio-cultural aspects of the design model.

The proposition that environment is of equal importance to time and space in the study of culture suggests that a three-dimensional approach may be a useful method for studying the process of cultural evolution. This possibility is tested by detailed investigations into the history and natural habitat of the prehistoric Hohokam Culture. This culture developed an extensive system of irrigation agriculture in the Gila River valley of southern Arizona about A. D. 1-1400. The study is carried out on the processual as well as analytical level of enquiry whereby primary attention was given to the relationship between environment and culture. This emphasis is particularly relevant in the case of the arid conditions of the region in which the Hohokani Culture developed. The interaction of the primary environmental agents, water and soil, and the cultural agent, prehistoric man, is delineated in terms of the natural processes of soil development and movement of water in the region as well as the cultural process of irrigation agriculture. During all phases of the River liohokarn Culture the relationship between soil, water, and man was interdependent and their functional interaction was exposed to the forces of the active environment, which may have become critical. An attempt is made to arrive at an interpretation along these lines for the terminal period of the Hohokam Culture at Snaketown, a major prehistoric site near Chandler, Arizona. While no definite conclusions are derived, the evidence, presented by means of inferential analysis, points strongly towards environmental causation. The impact of the prevailing climatic conditions at the end of the 13th century may have upset the precarious balance between water and soil and thus the livelihood of the desert dwellers. These events led inevitably to the termination of the Hohokam Culture.

Papago Indian fields located in southern Arizona and northern Sonora, Mexico are examples of a food production strategy that was developed within the constraints of a water-limited environment. Although only a small percentage of the fields cultivated at the turn of the century remain in cultivation, extant fields are vestiges of an agricultural tradition that has persisted in arid lands for centuries. An examination of the documentary history of non-Indian observations of Papago agriculture and water control from 1697 to 1934 reveals numerous practices and features that are no longer apparent within or around remaining fields. Yet by learning from oral historical accounts of elderly Papago, and analyzing O'odham lexemes (native Papago terms) which guide farmers' management of fields, it is possible to gain a sense of folk science which Papago developed to successfully farm without permanent surface water reserves. Selected concepts from the folk science of the Papago are used as a point of departure in understanding the ecological processes which function within their fields. Standard field ecology methods were adapted to empirically test certain hypotheses relating to these ecological processes. Results include confirmation that Papago fields are situated in a variety of physiographic positions, and that ‘ak-ciñ arroyo mouth' farming is a misnomer. Papago crops exhibit many of the same drought-escaping adaptations as wild summer desert ephemerals for seed production during the brief summer rainy season, which varies from year to year in the date of its initiation. These adaptations greatly contribute to crop success. There are no significant differences in the diversity of herbaceous plants found in Papago fields compared to the diversity found in adjacent, uncultivated environments. Of the many nutrients analyzed in cultivated and uncultivated floodplain soils, only potassium was significantly richer in fields than in uncultivated floodplains; other differences were statistically insignificant. Floodwashed organic detritus, rather than the floodwaters themselves, appear to play the major role in renewing field soil fertility in certain localities. It is concluded that indigenous concepts which have long guided the management of traditional agricultural systems are of heuristic value in understanding how these farming systems function ecologically.

Axelrod (1958) suggested that the late Tertiary shift in regional climate -- the elimination of summer rains -- had a profound influence on the evolution of biotic provinces in the American southwest. In particular, the taxa endemic to biotic provinces characterized by summer drought, e.g., the Mojave Desert, should be derived from ancestors that likely inhabited regions of summer rain, e.g., the Chihuahuan Desert. Further, the derived features of summer-drought taxa should be related to water stress. I examined Axelrod's thesis, using a combination of phylogenetic systematics, physiological ecology, and vicariance biogeography. The first chapter is a cladistic study of the pinyon pines, 13 taxa of small trees that range from the summer-wet regions of Mexico to the summer drought regions of Nevada and California. A parsimony analysis using twenty morphological characters showed that the most recently derived pinyons are from regions of summer drought. The "summer-drought" taxa are characterized by relatively few needles per fascicle. Because fewer needles per fascicle results in a reduction in the needle surface-to-volume ratio, Haller (1965) hypothesized that fewer needles in pines is an adaptation to reduce transpirational water loss. The second chapter reports on a two year study of the xylem pressure potentials of single- and double-needled fascicles of hybrid pinyons in central Arizona. The results showed no significant differences between single- and double-needles. I concluded that either needle morphology does not effect water relations, or that the relatively high precipitation during the study did not allow significant water stress to occur. The third chapter uses the methods of vicariance biogeography to search for a common pattern of relationship between southwestern biotic provinces, as indicated by the relationships of their endemic taxa. Using a biogeographic parsimony analysis, I compared the area cladograms of six taxa -- junipers, pinyon pines, the composite Palafoxia, hedgehog cactus, desert tortoises, and gecko lizards. The most parsimonious area cladogram supports Axelrod's (1958) hypothesis, but also shows that some taxa, notably the junipers, support other patterns of area relationships, e.g., summer-drought primitive. I suggest that there is no single pattern of area relationships because of the effects of the Pleistocene (including dispersal and extinction) and vicariance events other than the Tertiary climatic change, e.g., the separation of the Baja peninsula from mainland Mexico during the Miocene.

No description available.

"Last biannual progress report and final report describing work under NASA contract no. NAS5-21812."

The grain amaranths, Amaranthus cruentus and Amaranthus hypochondriacus have been promoted as grain-bearing plants of possible high productivity in saline or hot arid habitats. To investigate these claims, seeds of both species were germinated at 10, 15, 20, 25, 30, 35 and 40°centigrade. Germination percentage for both species was above 90% after four days at 20, 25, 30, and 35°C. Germination was negligible at 10 and 15°C and very low at 40°C. Seeds were germinated in isotonic solutions of PEG and NaCl at 0.0, -0.2, -0.4, -0.5, -0.6, -0.8, and -1.0 MPa osmotic potential at 30°C. Germination percentage was high in the range 0.0 to -0.4 MPa and dropped rapidly to zero in the -0.6 to -1.0 MPa range. Differences due to chemical effects were significant. Species differences were not. Radicles and hypocotyls were measured after six days in the above media. PEG was more inhibitory of seedling growth than was NaCl and generally inhibited A. cruentus more than A. hypochondriacus. This was also true of NaCl. All growth functions were slightly inhibited at 0.0 to -0.4 MPa and very inhibited above -0.6 MPa. PEG radically increased root/shoot ratio in both species.

Differential adaptations of barley (Hordeum vulgare L.) and wheat (Triticum spp.) genotypes suggest that they be evaluated under multi-environmental conditions. The objectives of this study were to determine if small grain genotypes, bred for various moisture conditions, respond differently in terms of yield, water use, and rooting pattern to contrasting moisture conditions. Eight small grain genotypes were compared under a gradient of water from 89 to 404 mm (plus 254 mm of stored water) in a field study at Marana, AZ. A barley bred for low input conditions had greater root density in the subsoil and used moisture earlier in the season when compared to a high input barley (WestBred Gustoe). The cultivars bred for high input conditions required more water for optimum yield compared to those bred for low input conditions.

[Truncated abstract] Generally hydrologic and ecologic models operate on arbitrary time and space scales, selected by the model developer or user based on the availability of field data. In reality rainfall is highly variable not only annually, seasonally and monthly but also the intensities within a rainfall event and infiltration properties on semi-arid hillslopes can also be highly variable as a result of discontinuous vegetation cover that form mosaics of areas with vegetation and areas of bare soil. This thesis is directed at improving our understanding of the impacts of the temporal representation of rainfall and spatial heterogeneity on model predictions of hydrologic thresholds and surface runoff coefficients on semi-arid landscapes at the point and hillslope scales. We firstly quantified within storm rainfall variability across a climate gradient in Western Australia by parameterizing the bounded random cascade rainfall model with one minute rainfall from 15 locations across Western Australia. This study revealed that rainfall activity generated in the tropics had more within storm variability and a larger proportion of the storm events received the majority of rain in the first half of the event. Rainfall generated from fontal activity in the south was less variable and more evenly distributed throughout the event. Parameters from the rainfall analysis were then used as inputs into a conceptual point scale surface runoff model to investigate the sensitivity of point scale surface runoff thresholds to the resolution of rainfall inputs. This study related maximum infiltration capacities to average storm intensities (k*) and showed where model predictions of infiltration excess were most sensitive to rainfall resolution (ln k* = 0.4) and where using time averaged rainfall data can lead to an under prediction of infiltration excess and an over prediction of the amount of water entering the soil (ln k* > 2). For soils susceptible to both infiltration excess and saturation excess, total runoff sensitivity was scaled by relating drainage coefficients to average storm intensities (g*) and parameter ranges where predicted runoff was dominated by infiltration excess or saturation excess depending on the resolution of rainfall data were determined (ln g* <2). The sensitivity of surface runoff predictions and the influence of specific within storm properties were then analysed on the hillslope scale. '...' It was found that using the flow model we still get threshold behaviour in surface runoff. Where conditions produce slow surface runoff velocities, spatial heterogeneity and temporal heterogeneity influences hillslope surface runoff amounts. Where conditions create higher surface runoff velocities, the temporal structure of within storm intensities has a larger influence on runoff amounts than spatial heterogeneity. Our results show that a general understanding of the prevailing rainfall conditions and the soil's infiltration capacity can help in deciding whether high rainfall resolutions (below 1 h) are required for accurate surface runoff predictions. The results of this study can be considered a contribution to understanding the way within storm properties effect the processes on the hillslope under a range of overall storm, slope and infiltration conditions as well as an improved understanding of how different vegetation patterns function to trap runoff at different total vegetation covers and rainfall intensities.