Measurement and Modeling of Reduced-Gravity Fluid Distribution and Transport in Unsaturated Porous Plant-Growth Media

The effect of reduced gravity on the balanced management of liquid, gaseous and ionic fluxes in unsaturated porous media remains a central challenge for plant-based bio-regenerative life support systems needed for long-duration space missions. This research investigated how shifting capillary and gravitational forces alter the sample-scale transport and distribution of fluids in mm-sized porous ceramic aggregates. Measurements in variably saturated media conducted on the International Space Station in microgravity ($sim1cdot10^{-3} g_{earth}$) and measurements during parabolic flight in variable gravity encompassing microgravity, terrestrial gravity and hypergravity ($sim1.8 g_{earth}$) were supported by numerical modeling based on fundamental, earth-derived soil-physical relationships. Measurements of water fluxes in rigid saturated media suggested Darcian flow unaffected by gravity. Observations of hydraulic potential and sample water content were used to estimate the primary draining and wetting water-retention characteristic (WRC). Terrestrial parameterizations of the WRC were largely unaffected by reduced gravity. However, because the WRC is hysteretic, heterogenous water-content distributions resulted within the confines of the primary draining and wetting characteristics. Ensuing distributions were fundamentally different from terrestrial observations and were stable in the absence of a significant gravity gradient. We showed that these distributions, though unexpected, could be predicted using the Richards equation. One consequence of altered water distribution could be the reduction in, and increased tortuosity of, continuous gas-filled pathways for diffusive transport compared to terrestrial estimates. Measurements of oxygen diffusion in microgravity suggested reduced diffusivities during draining. These observations, particularly for the smaller particle-sized media, were suggestive of the delayed formation of critical air-filled pathways at lower water contents. This dissertation further uses a case history of a stratified root-zone developed based on water-retention characteristics of different particle-sized media. The root-zone design provided a more uniform water-content distribution at terrestrial gravity suggested to provide more optimal conditions for root growth. Additionally, the design and testing of a novel integrated sensor for measurements of water content based on the dissipation of heat and estimation of nutrient status based on electrical resistivity are discussed. These results should provide insights into microgravity fluid distribution and transport contributing to the design and implementation of controllable plant-growth systems for use in microgravity and future planetary habitats

MONITORING ECOLOGICAL INTEGRITY IN THE CANYON GRASSLANDS: PLANT SPECIES AND ECOSYSTEM INDICATORS

Our objectives were to identify relationships between ecological integrity of the plant community, including the rare perennial forb Silene spaldingii Wats. (Spalding's catchfly), and external variables such as cattle grazing and weather, in the canyon grasslands in southeast Washington. From 3-5 years of data, we selected indicators from 200+ plants and functional groups measured by canopy and soil cover, frequency, and species richness metrics. Selected indicators differed between five ecological sites that were experimentally grazed for two to three years and ungrazed for more than five years on two units. From 2009 to 2011, we also compared 30 plant community variables between sites that contained the threatened Silene spaldingii and otherwise comparable sites without the plant using logistic regression. We regressed Silene spaldingii counts and reproductive effort against a combination of plant community and weather variables.Ecological integrity was generally stable or decreased during our study on grazed and ungrazed pastures at both units and on Silene spaldingii habitat. We identified increases in cover and species richness of exotic total species, exotic and native annual forbs, native perennial forbs, soil surface and bare soil, but indicators were not clearly associated with cattle grazing. Silene spaldingii absence was associated with higher cover of total exotic species, native annual forbs, and exotic annual forbs and grasses. Variation in Silene spaldingii counts and reproductive effort were associated with increases in native annual forb cover, exotic annual grass and forb species richness and cover, and exotic perennial grass species richness. Multiple plant community and Silene spaldingii variables were associated with weather, indicating the importance of understanding these relationships when considering ecological integrity, experimental grazing, and rare plant populations. Results indicate that managers should monitor the cover and species richness of exotic and annual species to understand changes in ecological integrity and Silene spaldingii demographics. If sites cross a threshold into a degraded annual-dominated state, integrity of the ecosystem may be permanently lost

Hildegard von Hohenthal

von Wilhelm Heins

Plan und Aufruf eines ehrlichen Vaterlandsfreundes zu einer Hauswirthschaftlichen Verbrüderung und einem Kreuzzuge gegen die Tirannei des Luxus und der gegenwärtigen Theurung : zunächst der Aufmerksamkeit seiner Chursächsischen Brüder und Schwestern empfohlen, welche im Begriffe stehen, eine Haushaltung anzufangen, oder sich von jenen Tirannen zu dem Entschlusse übermannen lassen wollten, dem Glücke des ehelichen Lebens zu entsagen

[Gottlob Heinrich Heinse

Towards Using Time-Lapse Electrical Resistivity Imaging for Improved Subsurface Snowmelt Characterization

In the intermountain west, snowmelt accounts for the majority of the annually available water. Understanding the fate of snow packs in the melting phase and particularly the infiltration of snowmelt is therefore central for maximizing the harvestable water and for maintaining the quality of snowmelt. Some of the open questions at the field-scale regard the localized infiltration of water and the nature and patterns of subsurface flow in the soil overlying bedrock. Electrical resistivity imaging (ERI) is known to be able to noninvasively image processes if state variables (i.e. water content) associated with the processes give rise to contrasts in the electrical conductivity. In the Vadose zone, the interpretation of such images is hampered by the equivalency of different model solutions. However, in time-lapse measurements, changes in electrical resistivity can be more directly related to changes in water content. In this way, flow processes in the subsurface can be characterized with high spatial and temporal resolution. The presented study was conducted within the well characterized and instrumented TWDEF experimental watershed in the Cache National Forest close to Logan, UT. To monitor the spatio-temporal evolution of snow melt, we installed 72 Electrodes with 5 m spacings on a sloping profile in the previous autumn. Automated measurements at this remote site were collected daily at 5 p.m. over several weeks using a Wenner/Schlumberger acquisition array. Measured data were inverted to produce apparent resistivity images of the subsurface. Subsequent temperature correction and differential comparison of temporal changes in subsurface resistivity were accompanied by soil surveys and depthto-bedrock soundings that guided in the interpretation and calibration of the measurements. Results suggest localized infiltration of snowmelt and subsurface flow bounded by non-conductive layers. Such behavior is consistent with visual observations of localized snowpack decreases and surface runoff patterns

Improving Root Zone Performance Physical and Numerical Modeling of a Layered Plant-growth Medium

Growing media in greenhouses and nurseries are selected based on gas exchange, control of the liquid phase and nutrient holding capability. In an effort to maintain favorable aeration and to avoid nutrient/salinity buildup, irrigated and free draining root zones operate under suboptimal water and nutrient use efficiencies. A novel layered plantgrowth medium was designed to improve the efficiency of water and nutrient application and promote more uniform root density compared to conventional containerized plant growth media. Our objectives were to (1) design and model an optimized root zone system using layered media, (2) instrument the root zone to monitor the water content distribution and track nutrient release and transport, and (3) compare the layered media system to conventional, non-layered plant growth media. The root-zone system is comprised of layered Ottawa sand, where watering is achieved by maintaining a shallow saturated layer at the bottom of the column and allowing capillarity to draw water upward. Coarser particle sizes form the bottom layers with finer particles sizes forming the layers above. The depth of each layer was chosen to optimize water content based on the wetting water retention curves retaining saturation between 50 and 85 percent. The saturation distribution was verified by dual-probe heat-pulse sensors, while the nutrient concentration was sensed by in-situ electrical conductivity measurements. Hydrus-1D was used to model the dynamic response of nutrient transport and root water uptake during diurnal cycling of transpiration. This design should provide a more optimal rootzone environment than conventional potting soils by maintaining a uniform water content profile and on-demand water supply

Ardinghello und die glückseeligen Inseln

[Wilhelm Heinse]Vorlageform der Veröffentlichungsangabe: Lemgo, im Verlage der Meyerschen Buchhandlun