Call number: LD2668 .T4 1986 S237 / Master of Science / Agronomy

The SMAPVEX12 (Soil Moisture Active/Passive Validation Experiment 2012) was carried out over the summer of 2012 in Manitoba, Canada. The goal of the project was to improve the accuracy of satellite-based remote sensing of soil moisture. Data were gathered during a 42-day field campaign with surface measurements on 55 different agricultural fields in south-central Manitoba. The extended duration of the campaign, contrast in soil textures, and variety of crop types over the study region provided an excellent range of soil moisture and vegetation conditions. The study fields ranged from bare to fully vegetated, with volumetric soil moisture levels spanning a range of almost 50%. Remotely sensed data were collected on 17 days by aircraft at 1.4 Ghz with a microwave radiometer at two different resolutions. Observed brightness temperatures from the radiometer showed a typical inverse relationship to the near simultaneous soil moisture measurements from the field. Field-by-field relationships using all sampling dates with both soil and emissivity data were all shown to be significant with the exception of two of the pasture fields and a soybean field. Linear regressions across multiple fields and by flight lines also had statistically significant slopes. The significance of all these relationships improved with the removal of pasture fields from the analysis. On most fields, the sensitivity (slope) of the relationship and correlation coefficient (R2) between emissivity and observed soil moisture increased when vegetation and roughness effects were taken into account. The b parameter that relates vegetation water content to optical depth in the tau-omega model was optimized using the collective slope and R2 values of the individual fields. A b parameter value of 0.06 for horizontal polarization and 0.13 for vertical polarization were found to be optimal across the range of all fields in this analysis. / May 2016

Philosophiae Doctor - PhD / The Cape Floristic Region (CFR) of southern Africa is one of the world’s most unique biodiversity hotspots. However, this biodiversity continues to be threatened by habitat loss due to rapid urbanisation, agriculture and alien vegetation encroachment, and now, by future groundwater extraction and climate change. Previous work had shown that soil moisture is important in structuring wetland plant communities at fine-scale. What is not fully known, however, is how the spatial distribution of species at a local scale is related to soil hydrology and what the response in the future of species distributions will be to perturbations arising from changes in climate or subsurface moisture in the future. The current research investigated the water regime of the Restionaceae which is a key family in the Fynbos biome and the implications of possible changes in soil hydrology caused by climate change in communities within this region. The Restionaceae were particularly appropriate because they are shallow rooted perennials with the ability to tolerate a wide range of water regimes which allows them to successfully co-habit within mixed plant communities as segregated clusters along fine-scale hydrologic gradients. Vegetation survey counts for the presence of these species along with measurements of soil water table depth and moisture content data generated from eight small-scale plots (50 x 50 m) were used to investigate the possible hydrological niches and to envision the potential impacts of a substantial reduction in rainfall and an increase in temperature as projected by Global Climate Models (GCMs) on the structure of Restionaceae communities in seasonal wetlands by 2100. A comparative analysis of the effects of two extreme Representative Concentration emission Pathways (RCP2.6 and RCP8.5) on significant hydrological variables to plant water regimes was carried out. The IPCC AR5 report describes the RCP8.5 emissions scenario as the likely ‘business as usual’ scenario where emissions continue to rise through the 21st century while the RCP2.6 scenario assumes that emissions peak between 2010 and 2020 and substantially subside thereafter.

The definition of the principle of effective stress and its implications have been examined for saturated and partly saturated soils. The results of a series of oedometer and all round compression tests of partly saturated and fully saturated soils are presented. These results together with additional experimental data indicate that most soils, from sands right through to clays, exhibit behaviour which, below a critical degree of saturation, cannot be accounted for by the effective stress principle. In sands the critioal degree of saturation appears to be below 50%. In clays, however, the critical degree of saturation is upwards of 85%. An explanation for the observed behaviour of partly saturated soils is offered. It is apparent that structural changes resulting from a change of pressure deficiency in a soil are very different from those resulting from an equivalent change in applied stress. The investigation as a whole indicates that, below the critical degree of saturation, the concept of effective stress in a partly saturated soil is not valid. It is suggested that the term 'intergranular stress' is more suitable than the term 'effective stress' since its use does not imply the validity of the principle of effective stress. The practical significance of the investigation is discussed briefly and the lines along which further research would prove profitable are indicated.

Soil moisture estimation using Sentinel-1 radar data The main aim of this diploma thesis was to find and quantify the relationship between the intensity of backscatter from the Sentinel-1 radar data and the volume soil moisture at the level of agricultural fields. The research was conducted in three areas, in the first part there were two vegetation-free fields near the Thessaloniki (Greece), and information about soil moisture was obtained from own measurements using a thermogravimetric method. The second part drew data from the freely available ISMN database and the research was carried out on agricultural fields during the vegetation season in northwest Germany. The third part used soil moisture data from the Czech Hydrometeorological Institute (ČHMÚ) and the area of interest was two grassed areas of the airport and one agricultural field. Correlation was measured by calculating the determination coefficient and by using the linear regression an equation for calculating the soil moisture from the radar backscatter was compiled. High dependence has been confirmed when VV polarization with constant surface roughness were examined. In the case of surfaces with varying roughness and vegetation cover, only low correlation was found, similarly with using VH polarization. Key words: radar, SAR, Sentinel-1, soil...

As climate warms during the 21st century, the resultant changes in water availability are a vital issue for society, perhaps even more important than the magnitude of warming itself. Yet our climate models disagree in their forecasts of water availability, limiting our ability to plan accordingly. This thesis investigates future water availability projections from Coupled Ocean-Atmosphere General Circulation Models (GCMs), primarily using two water availability measures: soil moisture and the Supply Demand Drought Index (SDDI). Chapter One introduces methods of measuring water availability and explores some of the fundamental differences between soil moisture, SDDI and the Palmer Drought Severity Index (PDSI). SDDI and PDSI tend to predict more severe future drought conditions than soil moisture; 21st century projections of SDDI show conditions rivaling North American historic mega-droughts. We compare multiple potential evapotranspiration (EP) methods in New York using input from the GISS Model ER GCM and local station data from Rochester, NY, and find that they compare favorably with local pan evaporation measurements. We calculate SDDI and PDSI values using various EP methods, and show that changes in future projections are largest when using EP methods most sensitive to global warming, not necessarily methods producing EP values with the largest magnitudes. Chapter Two explores the characteristics and biases of the five GCMs and their 20th and 21st century climate projections. We compare atmospheric variables that drive water availability changes globally, zonally, and geographically among models. All models show increases in both dry and wet extremes for SDDI and soil moisture, but increases are largest for extreme drying conditions using SDDI. The percentage of gridboxes that agree on the sign of change of soil moisture and SDDI between models is very low, but does increase in the 21st century. Still, differences between models are smaller than differences between SDDI and soil moisture projections. Chapter Three addresses the three major differences between SDDI and soil moisture calculations that shed light on why their future projections diverge: evaporation approximations, dependence on previous months' conditions, and the inclusion of additional variables such as runoff. We implement various changes in SDDI and a GCM vegetation scheme to test the sensitivity of each measure and to evaluate which alterations increase the similarity between SDDI and soil moisture. In addition to deconstructing the differences between SDDI and soil moisture, we analyze their projections regionally in Chapter Four. In seven regions (the southwest U.S., southern Europe, eastern China, eastern Siberia, Australia, Uruguay and Colombia), we 1) assess the forecasts of future water availability changes, 2) compare the atmospheric dynamical processes that produce rainfall and drought in the real world to the way it occurs in individual GCMs, 3) determine how these processes change as global temperatures increase, and 4) identify the most likely scenarios for future regional water availability. Chapter Five summarizes key findings by chapter, enumerating this dissertation's contributions to the field. It then discusses the limitations of existing models and measures, and suggests potential solutions for overcoming their predictive shortfalls. Finally, the chapter concludes with a proposal for future research to expand upon this dissertation work. This thesis highlights the global and zonal differences between two water availability measures, SDDI and soil moisture and identifies regions where they agree and disagree in 21st century modeled scenarios. It provides an explanation for differing projections in soil moisture and SDDI and proves that it is possible to bring convergence to their future projections, which is also applicable to PDSI. Finally, a detailed analysis of climatic changes from five GCMs made it possible to present the most likely scenarios for 21st century water availability in seven regions.

abstract: Soil moisture (θ) is a fundamental variable controlling the exchange of water and energy at the land surface. As a result, the characterization of the statistical properties of θ across multiple scales is essential for many applications including flood prediction, drought monitoring, and weather forecasting. Empirical evidences have demonstrated the existence of emergent relationships and scale invariance properties in θ fields collected from the ground and airborne sensors during intensive field campaigns, mostly in natural landscapes. This dissertation advances the characterization of these relations and statistical properties of θ by (1) analyzing the role of irrigation, and (2) investigating how these properties change in time and across different landscape conditions through θ outputs of a distributed hydrologic model. First, θ observations from two field campaigns in Australia are used to explore how the presence of irrigated fields modifies the spatial distribution of θ and the associated scale invariance properties. Results reveal that the impact of irrigation is larger in drier regions or conditions, where irrigation creates a drastic contrast with the surrounding areas. Second, a physically-based distributed hydrologic model is applied in a regional basin in northern Mexico to generate hyperresolution θ fields, which are useful to conduct analyses in regions and times where θ has not been monitored. For this aim, strategies are proposed to address data, model validation, and computational challenges associated with hyperresolution hydrologic simulations. Third, analyses are carried out to investigate whether the hyperresolution simulated θ fields reproduce the statistical and scaling properties observed from the ground or remote sensors. Results confirm that (i) the relations between spatial mean and standard deviation of θ derived from the model outputs are very similar to those observed in other areas, and (ii) simulated θ fields exhibit the scale invariance properties that are consistent with those analyzed from aircraft-derived estimates. The simulated θ fields are then used to explore the influence of physical controls on the statistical properties, finding that soil properties significantly affect spatial variability and multifractality. The knowledge acquired through this dissertation provides insights on θ statistical properties in regions and landscape conditions that were never investigated before; supports the refinement of the calibration of multifractal downscaling models; and contributes to the improvement of hyperresolution hydrologic modeling. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

Chiu, Ming Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 139-155). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.1.1 --- Environment of Hong Kong --- p.1 / Chapter 1.1.1.1 --- Flat land area --- p.1 / Chapter 1.1.1.2 --- Population --- p.2 / Chapter 1.1.1.3 --- Climate --- p.2 / Chapter 1.1.2 --- Landslides in Hong Kong --- p.4 / Chapter 1.1.2.1 --- Landslide history --- p.4 / Chapter 1.1.2.2 --- Government actions on landslide prevention --- p.7 / Chapter 1.1.3 --- Slopes in Hong Kong --- p.8 / Chapter 1.1.4 --- Slope stabilization --- p.10 / Chapter 1.1.4.1 --- Conventional methods of slope stabilization --- p.10 / Chapter 1.1.4.2 --- Biotechnical stabilization --- p.13 / Chapter 1.2 --- Situation in Hong Kong --- p.16 / Chapter 1.2.1 --- Slope protection in the past --- p.16 / Chapter 1.2.2 --- Government action on improving slope appearance --- p.16 / Chapter 1.2.3 --- Proprietary slope greening techniques --- p.19 / Chapter 1.3 --- Vegetation growth on slopes --- p.22 / Chapter 1.3.1 --- Basic requirements of plants --- p.22 / Chapter 1.3.2 --- Potential problems of proprietary systems on shotcreted cut slopes --- p.24 / Chapter 1.3.2.1 --- Steep gradient --- p.24 / Chapter 1.3.2.2 --- Thin soil --- p.24 / Chapter 1.3.2.3 --- Rainfall seasonality --- p.25 / Chapter 1.4 --- Current study --- p.26 / Chapter 1.4.1 --- Objectives --- p.26 / Chapter 1.4.2 --- Significance --- p.26 / Chapter 1.4.3 --- Thesis layout --- p.27 / Chapter Chapter 2 --- Soil water status and vegetation of cut slopes --- p.30 / Chapter 2.1 --- Introduction --- p.30 / Chapter 2.2 --- Materials and methods --- p.36 / Chapter 2.2.1 --- Study site --- p.36 / Chapter 2.2.2 --- In situ measurements and substrate sampling --- p.43 / Chapter 2.2.3 --- Physical properties of substrates on slopes --- p.43 / Chapter 2.2.3.1 --- Slope angle --- p.43 / Chapter 2.2.3.2 --- Substrate thickness --- p.43 / Chapter 2.2.3.3 --- Soil moisture --- p.43 / Chapter 2.2.3.4 --- Soil texture --- p.43 / Chapter 2.2.3.5 --- Bulk density --- p.44 / Chapter 2.2.3.6 --- Water retention capacity --- p.44 / Chapter 2.2.4 --- Chemical properties of substrates on slopes --- p.44 / Chapter 2.2.4.1 --- pH --- p.44 / Chapter 2.2.4.2 --- Conductivity --- p.45 / Chapter 2.2.4.3 --- Organic matter --- p.45 / Chapter 2.2.4.4 --- Total Kjeldahl nitrogen --- p.45 / Chapter 2.2.4.5 --- Mineral nitrogen (ammonium and nitrate) --- p.45 / Chapter 2.2.4.6 --- Carbon:Nitrogen --- p.46 / Chapter 2.2.4.7 --- Total phosphorus --- p.46 / Chapter 2.2.4.8 --- Available phosphorus --- p.46 / Chapter 2.2.4.9 --- Major extractable cations --- p.46 / Chapter 2.2.5 --- Green coverage on slopes --- p.46 / Chapter 2.2.6 --- Statistical analysis --- p.47 / Chapter 2.3 --- Results --- p.47 / Chapter 2.3.1 --- Rainfall characteristics --- p.47 / Chapter 2.3.2 --- Soil moisture --- p.49 / Chapter 2.3.3 --- Green coverage --- p.52 / Chapter 2.3.4 --- Physical properties of substrate on slopes --- p.55 / Chapter 2.3.5 --- Chemical properties of substrate on slopes --- p.57 / Chapter 2.4 --- Discussion --- p.61 / Chapter 2.4.1 --- Soil moisture and vegetation growth --- p.61 / Chapter 2.4.2 --- Soil nutrients and vegetation growth --- p.66 / Chapter 2.4.3 --- Other substrate properties and vegetation growth --- p.69 / Chapter 2.5 --- Summary --- p.75 / Chapter Chapter 3 --- Surface runoff and soil erosion of cut slopes --- p.76 / Chapter 3.1 --- Introduction --- p.76 / Chapter 3.2 --- Materials and methods --- p.84 / Chapter 3.2.1 --- Study site --- p.84 / Chapter 3.2.2 --- Experimental setup --- p.84 / Chapter 3.2.3 --- Surface runoff and soil loss --- p.88 / Chapter 3.2.4 --- Nutrient loss in runoff --- p.89 / Chapter 3.2.4.1 --- Total Kjeldahl Nitrogen --- p.89 / Chapter 3.2.4.2 --- Mineral nitrogen (ammonium and nitrate) --- p.89 / Chapter 3.2.4.3 --- Total phosphorus --- p.89 / Chapter 3.2.4.4 --- Available phosphorus --- p.90 / Chapter 3.2.5 --- Other substrate properties --- p.90 / Chapter 3.2.5.1 --- Soil texture --- p.90 / Chapter 3.2.5.2 --- Bulk density --- p.90 / Chapter 3.2.5.3 --- Soil compaction --- p.90 / Chapter 3.2.5.4 --- Water retention capacity --- p.90 / Chapter 3.2.5.5 --- Organic matter --- p.90 / Chapter 3.2.6 --- Vegetation coverage and green coverage on slope --- p.91 / Chapter 3.2.7 --- Statistical analysis --- p.91 / Chapter 3.3 --- Results --- p.91 / Chapter 3.3.1 --- Meteorological characteristics --- p.91 / Chapter 3.3.2 --- Surface runoff and runoff coefficient --- p.92 / Chapter 3.3.2.1 --- Surface runoff and runoff coefficient between different treatments --- p.92 / Chapter 3.3.2.2 --- Surface runoff and runoff coefficient between different proprietary systems --- p.97 / Chapter 3.3.3 --- Soil loss --- p.98 / Chapter 3.3.3.1 --- Soil loss between different treatments --- p.98 / Chapter 3.3.3.2 --- Soil loss between different proprietary systems --- p.99 / Chapter 3.3.4 --- Nutrient loss --- p.99 / Chapter 3.3.4.1 --- Nutrient loss between different treatments --- p.99 / Chapter 3.3.4.2 --- Nutrient loss between different proprietary systems --- p.104 / Chapter 3.3.5 --- Substrate properties of proprietary systems --- p.104 / Chapter 3.3.6 --- Vegetation coverage and green coverage --- p.107 / Chapter 3.3.7 --- Relationship between rainfall and erosional parameters --- p.110 / Chapter 3.4 --- Discussion --- p.117 / Chapter 3.4.1 --- Surface runoff and runoff coefficient between different treatments --- p.117 / Chapter 3.4.2 --- Relationship between rainfall characteristics and surface runoff --- p.122 / Chapter 3.4.3 --- Soil loss between different treatments --- p.125 / Chapter 3.4.4 --- "Relationship between rainfall characteristics, surface runoff and soil loss" --- p.126 / Chapter 3.4.5 --- Nutrient loss between different treatments --- p.128 / Chapter 3.4.6 --- Surface runoff and erosional losses between different proprietary systems --- p.129 / Chapter 3.5 --- Summary --- p.132 / Chapter Chapter 4 --- Conclusions --- p.134 / Chapter 4.1 --- Summary of major findings --- p.134 / Chapter 4.2 --- Implications of the study --- p.136 / Chapter 4.3 --- Limitations of the study --- p.137 / Chapter 4.4 --- Suggestions for further investigation --- p.138 / References --- p.139 / Appendices --- p.156

First order fire effects in mixed grass and tallgrass prairies may differ between current and historic fire regimes. To determine potential differences, the thermal dynamics of nine prescribed grassland fires and six experimental fires were evaluated. Fires were instrumented with dataloggers and arrays of up to twelve thermocouples set at heights ranging from -5 cm to 300 cm. Soil moisture and texture were documented, along with fuel characteristics. A series of experimental fires allowed soil moisture to be manipulated while minimizing other variables. Maximum temperature for the prescribed fires was 875°C at 75cm, and for the experimental fires 920°C at 10 cm. In experimental fires, the greatest temperature difference was at the surface with the dry substrate averaging 130°C higher than saturated. Average temperatures at -1 cm differed by 33°C. At 60°C, residence times in dry substrate averaged almost four minutes, while the average for saturated treatment was only 1 second. Surface residence times on dry substrate averaged over 7 minutes, almost 3 times longer than saturated. Soil moisture was shown to influence relative humidity and fine fuel moisture near the ground surface. An increased evaporation of soil water at the surface is suggested by a slight drop in subsurface temperatures as the flaming front moves over the surface. These data suggest that soil moisture affects fire intensity, decreasing temperatures at all levels of a fire. Temperatures and residence times were compared with data from studies documenting temperatures significantly affecting seed germination and edaphic effects at and below the surface. Temperatures increasing the germination of some seeds were found at all heights. Temperatures documented can be expected to decrease organic matter content and aggregate stability at the surface, slightly increasing erodibility. Thermal dynamics from the fires in this study represent a broad range of grassland fires under conditions common for prescribed fire. Soil moisture appears to significantly affect temperatures and residence times below, at, and above the soil surface. Data were compared with output from FOFEM 5.2 to access the applicability of FOFEM for use in mixed grass and tallgrass prairie. FOFEM consistently underestimated soil heating by up to 419°C.

Thesis (MSC.Agriculture)) --University of Limpopo, 2009. / The aim of this experiment was to evaluate the effect of moisture stress on tomato, using non-destructive remote sensing techniques and agronomic traits under field and greenhouse conditions. Two tomato cultivars Roma VF and Flora Dade were used for the trial. The soil was fertilized optimally for all nutrients to avoid other stresses except water stress; a 2x2 factorial experiment was conducted using two levels of water regimes (stressed vs. control (non-stressed)) having four replicates and two cultivars using a Completely Randomized Design. Pots were put under greenhouse and field conditions. Canopy temperature was measured using an infrared thermometer, NDVI values were recorded using a green seeker hand-held optical sensor unit and stomatal opening were determined using a leaf porometer. Other agronomic traits including days taken for 50% flowering, plant height, number of fruits per plant and fruit yield per plant were recorded. Leaf temperature in stressed plants was high as compared to non-stressed plants, whereas NDVI and stomata conductance values were low. Number of fruits per plant was low; each plant had 4.00 fruits under field conditions and 5.00 fruits per plant under greenhouse conditions as compared to 9.00 fruits under field conditions and 13.00 under greenhouse conditions for non stressed plants. Stressed plants were shorter as compared to non-stressed plants and days taken for 50% flowering were delayed in both cultivars for stressed plants. Stressed plants showed a sign of stress at early stages of plant development. Most of these signs were found on the plants rather than on the fruits, the shape of the main stem of a growing plant was one of the good indicators as it became thin and stringy under stressed conditions. The experiment showed that it is possible to evaluate the effect of moisture stress on tomato by the use of canopy temperature, NDVI, stomatal conductance and agronomic traits.