No description available.

Based upon literature search, field investigation, examination of the halophyte collection at the Environmental Research Laboratory in Tucson, Arizona, and an expert survey, 97 salt-tolerant plants have been identified for the use as landscape plants. The plants were screened at salinity levels between 5 and 40 ppt which are critical for plant survival. The globally gathered data revealed information about landscape criteria, such as aesthetic value, climate amelioration, soil stabilization, color, form and drought tolerance, which were organized into architectural, engineering and design categories. These landscape halophytes range from herbaceous ground covers to woody trees. The data were filed in a computer data base, including detailed information about the description and performance of every plant, habitat requirements, maintenance, landscape values and economic uses. The data base, which is continually up-dated, is a search-type, which functions as an information storage system and is designed to provide plant selection by needed characteristics or intended use.

No description available.

No description available.

No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

There is a need to understand the spatial distribution of soil taxonomic classes, the spatial distribution of potential biological soil crust, and soil properties related to wind erosion to address land use and management decisions in arid and semi-arid areas of the western USA. Digital soil mapping (DSM) can provide this information. Chapter 2 compared multiple DSM functions and environmental covariate sets at three geographically distinct semi-arid study areas to identify combinations that would best predict soil taxonomic classes. No single model or type of model was consistently the most accurate classifier for all three areas. The use of the “most important” variables consistently resulted in the highest model accuracies for all study areas. Overall classification accuracy was largely dependent upon the number of taxonomic classes and the distribution of pedons between taxonomic classes. Individual class accuracy was dependent upon the distribution of pedons in each class. Model accuracy could be increased by increasing the number of pedon observations or decreasing the number of taxonomic classes. Potential biological soil crust level of development (LOD) classes were predicted over a large area surrounding Canyonlands National Park in Chapter 3. The moderate LOD class was modeled with reasonable accuracy. The low and high LOD classes were modeled with poor accuracy. Prediction accuracy could likely be improved through the use of additional covariates. Spatial predictions of LOD classes may be useful for assessing the impact of past land uses on biological soil crusts. Threshold friction velocity (TFV) was measured and then correlated with other, easier-to-measure soil properties in Chapter 4. Only soils with alluvial surficial rocks or weak physical crusts reached TFV in undisturbed conditions. All soil surfaces reached TFV after disturbance. Soils with weak physical crusts produced the most sediment. Future work on wind erosion in the eastern Great Basin should focus on non-crusted/weakly crusted soils and soils formed in alluvium overlying lacustrine materials. Soils with other crust types are likely not susceptible to wind erosion. Threshold friction velocity in undisturbed soils with weak physical crusts and undisturbed soils with surficial rocks was predicted using a combination of penetrometer, rock cover, and silt measurements.

Bibliography: leaves 155-169. Studies the effect of nitrogen fertilizer on dry matter production under differing watering regimes. Investigates the accuracy of different crop and soil organic matter models for predicting crop yield, nitrogen uptake and changes in soil organic carbon and nitrogen. Compares the models with data from long-term field experiments on wheat in Australia and sorghum in Ethiopia. Finds that a higher crop yield and better nitrogen and water utilisation can be achieved if addition of nitrogen fertilizer is balanced with soil water.

The management and sustainable use of Central Australian rangelands for livestock production and conservation requires improved knowledge of the temporal and spatial distribution of primary production in this region. To provide such information, this thesis investigated methods that could rapidly and efficiently estimate regional herbage biomass production in these arid landscapes. Two different approaches were examined, using (1) ground-based or (2) satellite-based data sources. Soil moisture and herbage growth data were collected over several growth seasons and five landscape types in Central Australia, and the data used to develop a model of soil moisture balance and herbage production for the region. The model has few parameters and only requires inputs of rainfall and potential evaporation to predict daily soil moisture and plant growth. Moisture loss in the 0-500 mm soil profile was modelled using a negative exponential function that depends on available soil moisture and is driven by potential evaporation. The growth of herbage, whilst soil moisture is above wilting point, is a linear function of actual evapotranspiration, with the decay of plant material represented by a logistic curve through time. Soil moisture, herbage biomass and species composition assessments made at hectare and square kilometre scales at four locations within Central Australia were examined to determine if a small sample area could be used to accurately describe the soil and plant conditions at a landscape scale. Moisture levels of the 0-200 and 0-500 mm soil profiles from nine samples were analysed for the beginning and conclusion of a growth season, whilst herbage biomass and species composition from 50 samples were compared at the end of the growth season. Results suggest that mean soil moisture levels determined in a 1 ha area are comparable with mean values in the surrounding 1 km2 area. Herbage biomass and species richness for a square kilometre can be assessed at a hectare site for some landscape types, but a larger sampling area (> 1 ha) is recommended for most rangeland assessments. Satellite data (NOAA-11) were examined for their potential application in assessing primary productivity in Central Australia. Several image correction techniques were tested to minimise the adverse effects of atmospheric contamination and illumination. Two measures of atmospheric moisture: (1) radiosonde data and (2) temperature differences between bands 4 and 5 of the NOAA satellite (split-window) were used to explain variations in NOAA-11 normalised difference vegetation index (NDVI) on inert desert sites. The splitwindow approach provided the best single factor relationship (r2=0.63) and, when combined with scattering angle (illumination) effects, up to 81% of the variation in NDVI data could be explained. Field measurements of herbage biomass were correlated with four growth indices derived from NOAA-11 NDVI data. The influence of preflight and sensor degradation calibrations of Bands 1 and 2, and atmospheric correction techniques were also tested. Correlations between temporal sums of NDVI and herbage biomass data were relatively poor (r2<0.42) and unsuitable for herbage assessment in Central Australia. However, correlations between atmospherically corrected and background-adjusted maximum NDVI data and observed herbage biomass were strong (r2=0.91), that will allow primary production in the arid rangelands of Central Australia to be assessed rapidly and efficiently using remotely-sensed information.

"June 2002" / Bibliography: leaves 172-198. / viii, 198 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Proposes that the overall outcome of plant interactions along a temporal gradient of resource availability changes from positive during interpulses to negative during pulses. Examines negative interactions between 4 co-dominant chenopod scrubs in arid Acacia papyrocarpa woodlands. Negative interactions were more intense when conditions were least productive. Positive interactions between seedlings also changed over time, depending on the facilitation mechanism. Plant interactions seem to be most intense at the beginning of interpulses when plants are competing for diminishing water, or survivorship is enhanced in the favorable microsites provided by other plants. Later in the interpulse, interactions become less intense as conditions become more stressful and therefore survivorship and growth are affected more by abiotic conditions than plant interactions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Biology, 2002