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1
Young, Fred J. "Spatial variability of soil properties within a loess-covered, upland landscape /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9823319.
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Tong, Yanan. "Nitrogen loss assessment and environmental consequences in the loess soil of China /." Umeå : Dept. of Forest Ecology, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s284.pdf.
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Zhang, Shulan. "Soil hydraulic properties and water balance under various soil management regimes on the Loess Plateau, China /." Umeå : Dept. of Forest Ecology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005126.pdf.
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4
Muñoz-Castelblanco, José. "Comportement hydromécanique d'un loess naturel." Phd thesis, Université Paris-Est, 2011. http://pastel.archives-ouvertes.fr/pastel-00647891.
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Ce mémoire de thèse est consacré à l'étude expérimentale du comportement hydromécanique d'un lœss naturel non saturé effondrable provenant d'un site proche de la ville de Bapaume (nord de la France) dans une zone où des problèmes de tassement le long de la ligne nord du TGV ont été attribués à l'effondrement du lœss, du fait d'infiltrations d'eau. Un nouvel appareil triaxial permettant de mesurer localement l'ensemble des caractéristiques du loess non saturé (déformation, teneur en eau et succion) a été développé. La courbe de rétention d'eau, déterminée à l'aide d'un tensiomètre de haute capacité et de la méthode du papier filtre a fait l'objet d'une attention particulière : elle présente autour de la teneur naturelle une zone sans hystérésis bordée par deux boucles d'hystérésis des côtés secs et humides. L'analyse de la courbe de rétention et du phénomène d'hystérésis a été approfondie grâce à une étude microstructurale réalisée à l'aide de la porosimétrie au mercure et de la microscopie électronique à balayage. Une structure assez complexe composée d'un arrangement métastable de grains de limon secs (probablement liés par la recristallisation du calcaire) et d'une phase argileuse répartie de façon hétérogène a été mise en évidence. L'étude du comportement hydromécanique a compris une investigation de l'effondrement à partir de faibles valeurs de contraintes proches de la contrainte in-situ, à l'aide d'essais oedométriques à taux de déformation constant avec mesures de succion. Le maximum d'effondrement et une dépendance fonction de la vitesse de chargement ont été identifiés. Une campagne d'essais triaxiaux à différentes teneurs en eau constantes avec mesure de succion a permis de déterminer l'allure de la limite élastique du limon naturel dans un diagramme p/q, ainsi que ses variations avec la teneur en eau et la succion et confirmer l'écrouissage en succion
5
Peng, Rong, and 彭蓉. "Erosion in the Loess Plateau : scales and silos of the grain to green project, 1999-2003." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/207139.
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This thesis explores the relationship between environmental restoration and social-economic factors. It focuses on the erosion treatment on the Loess Plateau, especially the Grain to Green Project (GGP), the biggest national-range environmental treatment program in China in recent years. GGP produced significant impact on local landform, landuse and livelihood. On one hand, the program effectively controlled torrent by increasing soil aggregation; on the other hand, it lacked long-term perspectives and had underestimated the complexity of the environment and of local residents.
The thesis seeks to bridge the gaps between soil treatment policy and the actual effect. Research was conducted on soil erosion across multiple scales and key issues are generated based on typical cases. Findings from the research serve as guidelines for the following design proposition. The design applies hierarchical method, including both top-down and bottom-up interventions. First, a division method for erosion states was developed which can divide the erosion problem within the range of the yellow river into small catchment basins. Second, a typical catchment basin was selected as an example to show proposed strategy in three scales: catchment, slope and patches. The core design idea is to conserve resources and maximize output in sustainable ways. The fragmented land patches are integrated to complete the production model. The study site is planned according to field condition, such as erosion process, slope ratio, lighting, water resource and distance to settlements. Patches were identified using vegetation coverage and appropriate planting strategies were proposed accordingly.
In sum, the thesis is a critique of existing GGP. A new solution is proposed that can mitigate the conflict of soil erosion treatment and socio-economic development of local communities.published_or_final_version
Architecture
Master
Master of Landscape Architecture
6
Rhanor, Thomas. "Topographic Position and Land Cover Effects on Soil Organic Carbon Distribution of Loess-Veneered Hillslopes in the Central United States." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1260.
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Soil organic carbon (SOC) is important both for its influence on agricultural productivity and for its role in the carbon cycle. The distribution of SOC is highly variable at the field scale both horizontally and vertically; a portion of SOC's variability can be attributed to differences in vegetative cover and to slope position. This study characterized and compared SOC concentration to a depth of 2 meters across 6 loess-veneered watersheds in the central United States. Data were collected as part of the Shawnee Hills Loess Catenas project, a collaboration between the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service, USDA Forest Service, Purdue University, University of Kentucky, Southern Illinois University at Carbondale, and Illinois State Geological Survey, among others. The study consists of pairs of sites, one under forest cover and one grass cover, located in southern Illinois, southern Indiana, and western Kentucky. Bulk density and SOC data were calculated from genetic horizon samples taken from soil pits laid out as transects along slopes at each site. SOC concentrations were significantly higher under forest cover. Footslopes and toeslopes had significantly higher SOC densities than summits, shoulders, and backslopes. A three-part exponential decay model was the best fit for the relationship between SOC density and depth from the surface. The comparisons and models may be used to more accurately predict SOC concentration and carbon pool size on similar loess-veneered landscapes in the central United States.
7
Lu, Yuelai. "Soil conservation for sustainable land use : a decision-support model for the Loess Plateau, China." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266755.
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Sittig, Stephan [Verfasser]. "Sorption, Transformation and Transport of Sulfadiazine in a loess and a sandy Soil / Stephan Sittig." Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1077268904/34.
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9
Damane, Monica. "An investigation into the volume change characteristics of loess like soil in Mount Moorosi Village in Lesotho." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31497.
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The Mount Moorosi village is situated in the Senqu River Valley of southern Lesotho, within the Stormberg landform. The integrity and aesthetic appearance of nearly all the structures in this area are undermined by recurrent cracks. At present, no apparent institutionalised effort had been conducted to investigate the source of this problem. The crack patterns were associated with the possible volume change of the underlaying loess like soil. This soil has caused a disastrous failure to brittle civil engineering structures in various parts of the world. Its behaviour is attributed to sand and silt particles bonded by minerals, which become active upon saturation and induce hydrocollapse settlement. This study characterised the volume change properties of the underlaid deposits in Mount Moorosi. The research utilised representative samples from trial pits in the study region to perform laboratory experiments such as the Atterberg limits, wet sieving, sedimentation, free swell, x-ray diffraction, scanning electron microscope and slaking. The consolidated undrained tests and hydrocollapse potential were also determined from the GEOCOMP triaxial and Global Digital System oedometer, respectively. Results revealed that Mount Moorosi is generally underlaid by a more than 3 m thickness of low plasticity (9 to 17 %) silty-sandy loess. The material had significant warping (up to 27 mm) in linear shrinkage that illustrated potential inducement of detrimental stresses to the superimposed structures during drying. The identification and quantification of the mineralogy composition clearly evidenced the passive minerals (quartz, feldspar and mica) to be predominant (86 %), while the active phases (kaolinite, carbonates, sulfates, halides, the oxides and hydroxides of aluminum and iron) were subordinate (14 %), which substantiated potential soil settlement upon wetting. Furthermore, the micrographs depicted structures that synergistically enhanced the collapse properties of the tested deposits. These included the porous clays, silts bonded by clay and silts coated with clay, which all rendered a metastable fabric. A comparison of the stressstrain graphical plots from the consolidated undrained tests at the field and saturated moisture contents indicated a drastic reduction (up to 73 %) in deviator stress at saturated water content. This was attributed to the augmentation of the interparticle spaces, caused by a rise of up to 337 kPa in pore water pressure. Shear strength parameters obtained from Mohr’s failure envelopes were also decreased by up to 80 %. The hydrocollapse index measured from the oedometer tests ranged from 10 to 15 % at a vertical stress of 200 kPa. It indicated severe settlement problems for structures constructed on this soil. This was caused by the loss in shear strength of the soil under the saturated conditions and a high slaking mechanism that reached a maximum rating of 4. Generally, the mineralogy composition, morphology, saturated shear strength, slaking and hydrocollapse index collectively indicated the possibility of soil volume decrease. In fact, the check for serviceability limit state demonstrated a settlement that exceeded the tolerable value of 50 mm. The cracks observed on structures were, therefore, related to soil settlement. This study recommends further research on suitable ground techniques to minimise settlement, thereby improving the durability of structures. Moreover, investigations should be conducted to understand the pressure induced by warping during shrinkage.
10
Kouns, Carolina, and Yael Margulis. "Rock-magnetic and Soil Organic Carbon Proxies of Climate Change from Loess – Aeolian Sediments of Brittany, France." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445688.
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The aeolian sediment loess, which consists of mineral dust, is one of the most detailed terrestrial record of both global and regional climate changes. As climate changes in the past cover a much wider range of climate variability than humans have directly recorded, the soil memory of loess is vital for understanding the Earth’s climate system. By examining past climate records and analyzing past climate changes and factors that have instigated changes, inferences regarding future climate can be made. Therefore, the aim of this research was to define the specific depositional and post-depositional conditions of a loess sequence in Primel-Tr gastel, Brittany, north-western France. This was done by examining the magnetic susceptibility (MS), and loss on ignition (LOI) of 63 samples from the Primel-Tr gastel sequence. The result suggests that the lower part was formed during a relatively long, cold and dry period, with significant temperature oscillations, resulting in several periglacial phases. The data also shows an increase in the MS signal for the middle units, which then gradually decreases simultaneously as there is a sharp rise in the proportion of organic matter (OM). This is followed by a steep drop and finally an overall increase in OM, which suggests that this period has been characterized by both stadial and interstadial phases. The upper part displays a general increase in MS values, as well as increased organic matter, which implies a milder climate with increased temperatures. The study provides the first comprehensive estimate of the regional climate variability and provides a base towards a more comprehensive and overarching understanding of our climate system.
11
Presley, DeAnn R. "Genesis and spatial distribution of upland soils in east central Kansas." Diss., Kansas State University, 2007. http://hdl.handle.net/2097/288.
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Doctor of PhilosophyDepartment of Agronomy
Michel D. Ransom
Upland soils in east central Kansas have a complex genesis, often contain one or more paleosols, and form in multiple parent materials including loess, colluvium, residuum, and alluvium. Quaternary loess/paleosol investigations have largely ignored this region of Kansas, as the total loess thickness on uplands is <2 m thick. In this study, the objectives are to examine the morphology and genesis of the soils of interest and how these characteristics vary within soil profiles, across landscapes, and throughout the current series mapping extent. The series of interest include the Irwin, Konza, Dwight, and Ladysmith soil series. Methods used in this study include field descriptions and sampling, terrain analysis, micromorphological investigations, and laboratory characterization, including silt and clay mineralogy. Accelerator mass spectrometry (AMS) was used for numerical dating and determination of stable carbon isotope values (δ13C) for selected paleosols. Radiocarbon ages ranged from 24,000 to 19,000 yr BP and δ13C values were between -19 and -17 ‰ (PDB), indicating that the paleosols were formed in Gilman Canyon loess or the Severance formation, under a mix of C3 and C4 vegetation. Terrain analysis results illustrated that, in given drainage areas, the soil series were mapped on a wide range of slope positions. Field observations and terrain analysis confirmed no relationships between mollic epipedon thickness, solum thickness, paleosol thickness, or depth to the paleosol with respect to landform. Micromorphological investigations revealed increasing soil development with depth, i.e., the presence of two paleosols beneath the modern soil. Mean particle size and mineralogy vary geographically within individual series. Pedogenic carbonate accumulations and redoximorphic concentrations are common features of the soils of interest, and less common features include sodium and gypsum accumulations, slickensides, and redoximorphic depletions. Results from this study will be provided to the USDA-NRCS for use in future soil survey updates, and will contribute to Quaternary loess/paleosol knowledge in Kansas and the Great Plains.
12
Reuter, Hannes Isaak [Verfasser]. "Spatial crop and soil landscape processes under special consideration of relief information in a loess landscape / Hannes Isaak Reuter." Hannover : Technische Informationsbibliothek (TIB), 2016. http://d-nb.info/1095502832/34.
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Pihlap, Evelin [Verfasser], Prof Ingrid [Akademischer Betreuer] Kögel-Knabner, Kull Ph D. [Akademischer Betreuer] Ain, Prof Dr Johannes [Gutachter] Kollmann, Prof Tönu [Gutachter] Oja, Prof Dr Ülo [Gutachter] Mander, and Prof Dr Anja [Gutachter] Rammig. "Soil aggregate formation in soils derived from loess reclamation / Evelin Pihlap ; Gutachter: Prof. Dr. Johannes Kollmann, Prof. Tönu Oja, Prof. Dr. Ülo Mander, Prof. Dr. Anja Rammig ; Prof. Ingrid Kögel-Knabner, Ph.D. Ain Kull." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1230985212/34.
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Hughes, Matthew William. "Late Quaternary Landscape Evolution and Environmental Change in Charwell Basin, South Island, New Zealand." Phd thesis, Lincoln University. Agriculture and Life Sciences Division, 2008. http://theses.lincoln.ac.nz/public/adt-NZLIU20080214.132530/.
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Charwell Basin is a 6 km-wide structural depression situated at the boundary between the axial ranges and faulted and folded Marlborough Fault Zone of north-eastern South Island, New Zealand. The basin contains the piedmont reach of the Charwell River, and a series of late Quaternary loess-mantled alluvial terraces and terrace remnants that have been uplifted and translocated from their sediment source due to strike-slip motion along the Hope Fault which bounds the basin to its immediate north. The aim of this study was to provide an interdisciplinary, integrated and holistic analysis of late Quaternary landscape evolution and environmental change in Charwell Basin using terrain analysis, loess stratigraphy, soil chemistry and paleoecological data. The study contributes new understanding of New Zealand landscape and ecosystem responses to regional and global climatic change extending to Marine Isotope Stage (MIS) 6, and shows that climatically-forced shifts in biogeomorphic processes play a significant role in lowland landscape evolution.
Morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time, with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo-concave land elements. Paleotopographic analysis of a >150 ka terrace mantled by up to three loess sheets revealed multiple episodes of alluvial aggradation and degradation and, subsequent to river abandonment, gully incision prior to and coeval with loess accumulation. Spatial heterogeneity in loess sheet preservation showed a complex history of loess accumulation and erosion. A critical profile curvature range of -0.005 to -0.014 (d2z/dx2, m-1) for loess erosion derived from a model parameterised in different ways successfully predicted loess occurrence on adjacent slope elements, but incorrectly predicted loess occurrence on an older terrace remnant from which all loess has been eroded. Future analyses incorporating planform curvature, regolith erosivity and other landform parameters may improve identification of thresholds controlling loess occurrence in Charwell Basin and in other South Island landscapes.
A loess chronostratigraphic framework was developed for, and pedogenic phases identified in, the three loess sheets mantling the >150 ka terrace. Except for one age, infrared-stimulated luminescence dates from both an upbuilding interfluve loess exposure and colluvial gully infill underestimated loess age with respect to the widespread Kawakawa/Oruanui Tephra (KOT; 27,097 ± 957 cal. yr BP), highlighting the need for improvements in the methodology. Onset of loess sheet 1 accumulation started at ca. 50 ka, with a break at ca. 27 ka corresponding to the extended Last Glacial Maximum (eLGM) interstadial identified elsewhere in New Zealand. Loess accumulation through MIS 3 indicates a regional loess flux, and that glaciation was not a necessary condition for loess generation in South Island. Loess accumulation and local alluvial aggradation are decoupled: the youngest aggradation event only covers ~12 kyr of the period of loess sheet 1 accumulation. Older local aggradation episodes could not be the source because their associated terraces are mantled by loess sheet 1. In the absence of numerical ages, the timing of L2 and L3 accumulation is inferred on the basis of an offshore clastic sediment record. The upbuilding phase of loess sheet 2 occurred in late MIS 5a/MIS 4, and loess sheet 3 accumulated in two phases in MIS 5b and late MIS 6.
Biogenic silica data were used to reconstruct broad shifts in vegetation and changes in gully soil saturation status. During interglacial/interstadial periods (MIS 1, early MIS 3, MIS 5) Nothofagus¬-dominated forest covered the area in association with Microlaena spp grasses. Lowering of treeline altitude during glacial/stadial periods (MIS 2, MIS 3, MIS 5b, late MIS 6) led to reduction in forest cover and a mosaic of shrubs and Chionochloa spp, Festuca spp and Poa spp tussock grasses. Comparison of interfluve and gully records showed spatial heterogeneity in vegetation cover possibly related to environmental gradients of exposure or soil moisture. A post-KOT peak in gully tree phytoliths corresponds to the eLGM interstadial, and a shift to grass-dominated vegetation occurred during the LGM sensu stricto. Diatoms indicated the site became considerably wetter from ca. 36 ka, with peak wetness at ca. 30, 25 and 21 ka, possibly due to reduced evapotranspiration and/or increased precipitation from a combination of strengthened westerly winds and increased cloudiness, or strengthened southerly flow and increased precipitation. Human influence after ca. 750 yr BP led to re-establishment of grassland in the area, which deposited phytoliths mixed to 30 cm depth in the soil.
A coupled gully colluvial infilling/vegetation record showed that sediment flux during the late Pleistocene was ~0.0019 m3 m-1 yr-1 under a shrubland/grassland mosaic, and Holocene sediment flux was ~0.0034 m3 m-1 yr-1 under forest. This increase of 60% through the last glacial-interglacial transition resulted from increased bioturbation and down-slope soil transport via root growth and treethrow, which formed a biomantle as evidenced by slope redistribution of the KOT. These results contrast with sediment transport rates and processes hypothesised to occur contemporaneously in adjacent mountain catchments. This suggests that intraregional biogeomorphic processes can differ significantly depending on topography and geological substrate, with different landscapes responding in unique ways to the same climate shifts. Analysis of Quaternary terrestrial landscape evolution in non-glaciated mountainous and lowland areas must therefore consider spatial and temporal heterogeneity in sediment fluxes and underlying transport processes.
15
Stephen-Brownie, Charlotte Jane. "Earthquake-Induced Ground Fissuring in Foot-Slope Positions of the Port Hills, Christchurch." Thesis, University of Canterbury. Geological Sciences, 2012. http://hdl.handle.net/10092/9285.
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Following the 22 February 2011, MW 6.2 earthquake located on a fault beneath the Port Hills of Christchurch, fissuring of up to several hundred metres in length was observed in the loess and loess-colluvium of foot-slope positions in north-facing valleys of the Port Hills. The fissuring was observed in all major valleys, occurred at similar low altitudes, showing a contour-parallel orientation and often accompanied by both lateral compression/extension features and spring formation in the valley floor below. Fissuring locations studied in depth included Bowenvale Valley, Hillsborough Valley, Huntlywood Terrace–Lucas Lane, Bridle Path Road, and Maffeys Road–La Costa Lane.
Investigations into loess soil, its properties and mannerisms, as well as international examples of its failure were undertaken, including study of the Loess Plateau of China, the Teton Dam, and palaeo-fissuring on Banks Peninsula. These investigations lead to the conclusion that loess has the propensity to fail, often due to the infiltration of water, the presence of which can lead to its instantaneous disaggregation. Literature study and laboratory analysis of Port Hills loess concluded that is has the ability to be stable in steep, sub-vertical escarpments, and often has a sub-vertically jointed internal structure and has a peak shear strength when dry.
Values for cohesion, c (kPa) and the internal friction angle, ϕ (degrees) of Port Hills loess were established. The c values for the 40 Rapaki Road, 3 Glenview Terrace loess samples were 13.4 kPa and 19.7 kPa, respectively. The corresponding ϕ values were thought unusually high, at 42.0° and 43.4°.The analysed loess behaved very plastically, with little or no peak strength visible in the plots as the test went almost directly to residual strength.
A geophysics resistivity survey showed an area of low resistivity which likely corresponds to a zone of saturated clayey loess/loess colluvium, indicating a high water table in the area. This is consistent with the appearances of local springs which are located towards the northern end of each distinct section of fissure trace and chemical analysis shows that they are sourced from the Port Hills volcanics.
Port Hills fissuring may be sub-divided into three categories, Category A, Category B, and Category C, each characterised by distinctive features of the fissures. Category A includes fissures which display evidence of, spring formation, tunnel-gullying, and lateral spreading-like behaviour or quasi-toppling. These fissures are several metres down-slope of the loess-bedrock interface, and are in valleys containing a loess-colluvium fill. Category B fissures are in wider valleys than those in Category A, and the valleys contain estuarine silty sediments which liquefied during the earthquake. Category C fissures occurred at higher elevations than the fissures in the preceding categories, being almost coincident with bedrock outcropping.
It is believed that the mechanism responsible for causing the fissuring is a complex combination of three mechanisms: the trampoline effect, bedrock fracturing, and lateral spreading. These three mechanisms can be applied in varying degrees to each of the fissuring sites in categories A, B, and C, in order to provide explanation for the observations made at each. Toppling failure can describe the soil movement as a consequence of the a three causative mechanisms, and provides insight into the movement of the loess. Intra-loess water coursing and tunnel gullying is thought to have encouraged and exacerbated the fissuring, while not being the driving force per se. Incipient landsliding is considered to be the least likely of the possible fissuring interpretations.
16
Almond, Peter C. "Soils and geomorphology of a lowland rimu forest managed for sustainable timber production." Lincoln University, 1997. http://hdl.handle.net/10182/1782.
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Saltwater Forest is a Dacrydium cupressinum-dominated lowland forest covering 9000 ha in south Westland, South Island, New Zealand. Four thousand hectares is managed for sustainable production of indigenous timber. The aim of this study was to provide an integrated analysis of soils, soil-landform relationships, and soil-vegetation relationships at broad and detailed scales. The broad scale understandings provide a framework in which existing or future studies can be placed and the detailed studies elucidate sources of soil and forest variability. Glacial landforms dominate. They include late Pleistocene lateral, terminal and ablation moraines, and outwash aggradation and degradation terraces. Deposits and landforms from six glacial advances have been recognised ranging from latest Last (Otira) Glaciation to Penultimate (Waimea) Glaciation. The absolute ages of landforms were established by analysis of the thickness and soil stratigraphy of loess coverbeds, augmented with radiocarbon dating and phytolith and pollen analysis. In the prevailing high rainfall of Westland soil formation is rapid. The rate of loess accretion in Saltwater Forest (ca. 30 mm ka⁻¹) has been low enough that soil formation and loess accretion took place contemporaneously. Soils formed in this manner are known as upbuilding soils. The significant difference between upbuilding pedogenesis and pedogenesis in a topdown sense into an existing sediment body is that each subsoil increment of an upbuilding soil has experienced processes of all horizons above. In Saltwater Forest subsoils of upbuilding soils are strongly altered because they have experienced the extremely acid environment of the soil surface at some earlier time. Some soil chronosequence studies in Westland have included upbuilding soils formed in loess as the older members of the sequence. Rates and types of processes inferred from these soils should be reviewed because upbuilding is a different pedogenic pathway to topdown pedogenesis. Landform age and morphology were used as a primary stratification for a study of the soil pattern and nature of soil variability in the 4000 ha production area of Saltwater Forest. The age of landforms (> 14 ka) and rapid soil formation mean that soils are uniformly strongly weathered and leached. Soils include Humic Organic Soils, Perch-gley Podzols, Acid Gley Soils, Allophanic Brown Soils, and Orthic or Pan Podzols. The major influence on the nature of soils is site hydrology which is determined by macroscale features of landforms (slope, relief, drainage density), mesoscale effects related to position on landforms, and microscale influences determined by microtopography and individual tree effects. Much of the soil variability arises at microscales so that it is not possible to map areas of uniform soils at practical map scales. The distribution of soil variability across spatial scales, in relation to the intensity of forest management, dictates that it is most appropriate to map soil complexes with boundaries coinciding with landforms. Disturbance of canopy trees is an important agent in forest dynamics. The frequency of forest disturbance in the production area of Saltwater Forest varies in a systematic way among landforms in accord with changes in abundance of different soils. The frequency of forest turnover is highest on landforms with the greatest abundance of extremely poorly-drained Organic Soils. As the abundance of better-drained soils increases the frequency of forest turnover declines. Changes in turnover frequency are reflected in the mean size and density of canopy trees (Dacrydium cupressinum) among landforms. Terrace and ablation moraine landforms with the greatest abundance of extremely poorly-drained soils have on average the smallest trees growing most densely. The steep lateral moraines, characterised by well drained soils, have fewer, larger trees. The changes manifested at the landform scale are an integration of processes operating over much shorter range as a result of short-range soil variability. The systematic changes in forest structure and turnover frequency among landforms and soils have important implications for sustainable forest management.
17
Hughes, Matthew W. "Late Quaternary landscape evolution and environmental change in Charwell Basin, South Island, New Zealand." Lincoln University, 2008. http://hdl.handle.net/10182/305.
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Charwell Basin is a 6 km-wide structural depression situated at the boundary between the axial ranges and faulted and folded Marlborough Fault Zone of north-eastern South Island, New Zealand. The basin contains the piedmont reach of the Charwell River, and a series of late Quaternary loess-mantled alluvial terraces and terrace remnants that have been uplifted and translocated from their sediment source due to strike-slip motion along the Hope Fault which bounds the basin to its immediate north. The aim of this study was to provide an interdisciplinary, integrated and holistic analysis of late Quaternary landscape evolution and environmental change in Charwell Basin using terrain analysis, loess stratigraphy, soil chemistry and paleoecological data. The study contributes new understanding of New Zealand landscape and ecosystem responses to regional and global climatic change extending to Marine Isotope Stage (MIS) 6, and shows that climatically-forced shifts in biogeomorphic processes play a significant role in lowland landscape evolution. Morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time, with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo-concave land elements. Paleotopographic analysis of a >150 ka terrace mantled by up to three loess sheets revealed multiple episodes of alluvial aggradation and degradation and, subsequent to river abandonment, gully incision prior to and coeval with loess accumulation. Spatial heterogeneity in loess sheet preservation showed a complex history of loess accumulation and erosion. A critical profile curvature range of -0.005 to -0.014 (d²z/dx², m⁻¹) for loess erosion derived from a model parameterised in different ways successfully predicted loess occurrence on adjacent slope elements, but incorrectly predicted loess occurrence on an older terrace remnant from which all loess has been eroded. Future analyses incorporating planform curvature, regolith erosivity and other landform parameters may improve identification of thresholds controlling loess occurrence in Charwell Basin and in other South Island landscapes. A loess chronostratigraphic framework was developed for, and pedogenic phases identified in, the three loess sheets mantling the >150 ka terrace. Except for one age, infrared-stimulated luminescence dates from both an upbuilding interfluve loess exposure and colluvial gully infill underestimated loess age with respect to the widespread Kawakawa/Oruanui Tephra (KOT; 27,097 ± 957 cal. yr BP), highlighting the need for improvements in the methodology. Onset of loess sheet 1 accumulation started at ca. 50 ka, with a break at ca. 27 ka corresponding to the extended Last Glacial Maximum (eLGM) interstadial identified elsewhere in New Zealand. Loess accumulation through MIS 3 indicates a regional loess flux, and that glaciation was not a necessary condition for loess generation in South Island. Loess accumulation and local alluvial aggradation are decoupled: the youngest aggradation event only covers ~12 kyr of the period of loess sheet 1 accumulation. Older local aggradation episodes could not be the source because their associated terraces are mantled by loess sheet 1. In the absence of numerical ages, the timing of L2 and L3 accumulation is inferred on the basis of an offshore clastic sediment record. The upbuilding phase of loess sheet 2 occurred in late MIS 5a/MIS 4, and loess sheet 3 accumulated in two phases in MIS 5b and late MIS 6. Biogenic silica data were used to reconstruct broad shifts in vegetation and changes in gully soil saturation status. During interglacial/interstadial periods (MIS 1, early MIS 3, MIS 5) Nothofagus-dominated forest covered the area in association with Microlaena spp grasses. Lowering of treeline altitude during glacial/stadial periods (MIS 2, MIS 3, MIS 5b, late MIS 6) led to reduction in forest cover and a mosaic of shrubs and Chionochloa spp, Festuca spp and Poa spp tussock grasses. Comparison of interfluve and gully records showed spatial heterogeneity in vegetation cover possibly related to environmental gradients of exposure or soil moisture. A post-KOT peak in gully tree phytoliths corresponds to the eLGM interstadial, and a shift to grass-dominated vegetation occurred during the LGM sensu stricto. Diatoms indicated the site became considerably wetter from ca. 36 ka, with peak wetness at ca. 30, 25 and 21 ka, possibly due to reduced evapotranspiration and/or increased precipitation from a combination of strengthened westerly winds and increased cloudiness, or strengthened southerly flow and increased precipitation. Human influence after ca. 750 yr BP led to re-establishment of grassland in the area, which deposited phytoliths mixed to 30 cm depth in the soil. A coupled gully colluvial infilling/vegetation record showed that sediment flux during the late Pleistocene was ~0.0019 m³ m⁻¹ yr⁻¹ under a shrubland/grassland mosaic, and Holocene sediment flux was ~0.0034 m³ m⁻¹ yr⁻¹ under forest. This increase of 60% through the last glacial-interglacial transition resulted from increased bioturbation and down-slope soil transport via root growth and treethrow, which formed a biomantle as evidenced by slope redistribution of the KOT. These results contrast with sediment transport rates and processes hypothesised to occur contemporaneously in adjacent mountain catchments. This suggests that intraregional biogeomorphic processes can differ significantly depending on topography and geological substrate, with different landscapes responding in unique ways to the same climate shifts. Analysis of Quaternary terrestrial landscape evolution in non-glaciated mountainous and lowland areas must therefore consider spatial and temporal heterogeneity in sediment fluxes and underlying transport processes.
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Stark, Timothy D. "Mechanisms of strength loss in stiff clays." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/74771.
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On September 14, 1981 a major slide was discovered in the upstream slope of San Luis Darn, located about 100 miles southeast of San Francisco, California. The slide occurred at the end of a period of rapid drawdown of the reservoir. Although this was the longest and fastest drawdown in the life of the dam, 180 feet in 120 days, there had been seven previous cycles of drawdown, some nearly as severe as the one that preceded the slide.
Field measurements showed the slide was caused by the clayey slopewash material left in the foundation of the dam during construction. Although the slopewash was dry and extremely strong when the embankment was built, it apparently was weakened considerably when submerged beneath the reservoir and its strength was further degraded by cyclic loading effects as the reservoir level was raised and lowered during the 14 years preceding the slide.
The objective of this research was to gain a better understanding of the mechanisms of strength loss in the slopewash that resulted in the 1981 slide at San Luis Dam. This was accomplished using laboratory tests on undisturbed samples of slopewash, analyses of seepage through the embankment and foundation, finite element analyses of stresses in the dam during construction and operation of the reservoir, and conventional equilibrium slope stability analyses.
The laboratory tests showed that the shear strength of the slopewash decreases very quickly when the desiccated material is wetted. Wetting causes immediate reduction in shear strength to the fully softened value, and there is no lasting effect of consolidation by drying. After wetting the highly desiccated slopewash has the same strength as in the remolded, normally consolidated condition.
Tests that simulated cyclic changes in normal stress and shear stress like those during drawdown and refilling of the reservoir showed that further strength loss results from cyclic loading of the slopewash. Cyclic loading at stress levels below the fully softened peak strength result in continual shear displacement, and eventually, when the cumulative horizontal displacement reaches approximately ten inches, the shear strength is reduced to its residual value.Ph. D.
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Kelsey, Kurt L. "Use of the Revised Universal Soil Loss Equation (Rusle) to predict event soil loss /." Link to abstract, 2002. http://epapers.uwsp.edu/abstracts/2002/Kelsey.pdf.
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Tin, Lukić. "Боја лесно-палеоземљишних секвенци као показатељ палеоклиматских и палеоеколошких процеса." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2015. https://www.cris.uns.ac.rs/record.jsf?recordId=94363&source=NDLTD&language=en.
Full textAbstract:
Лесно-палеоземљишне секвенце на простору Војводине (северна Србија) представљају најзначајније регионалне палеоклиматске и палеоеколошке архиве. Испитивана секвенца Орловат- циглана на Тамишком, као и Дукатар педокомплекс V-S5 на Тителском лесном платоу изграђени су од седимената квартарне старости, формираних током глобалних палеоклиматских промена које су се одиграле током горњег и средњег плеистоцена. Промена боје између леса и палеоземљишта представља једно од најважнијих визуелних обележја ових литолошких чланова. Такође, наведене промене у блиској су вези са степеном развоја земљишта. Најизраженије разлике у боји између леса и палеоземљишта базиране су на заступљености два феромагнетична минерала- хематита и гетита. Поменути гвожђевити минерали имају значајну заступљеност у земљиштима и носиоци су записа о климатским и еколошким променама. Земљишта која садрже само, или готово искључиво гетит имају жуту боју. Када је присутан хематит боја углавном постане црвенкаста, због чињенице да црвени хематит веома успешно маскира жути гетит. Детаљним теренским и лабораторијским истраживањима поменутих лесно-палеоземљишних секвенци добијене су колориметријске вредности и вредности стенског магнетизма презентоване у оквиру ове дисертације. Боја лесно-палеоземљишних седимената у влажном и сувом стању одређена је применом Манселовог каталога боја земљишта, а рефлективност боја лесних и палеоземљишних узорака одређена је инструментално, помоћу тристимулусног колориметра. Колориметријске вредности дате су у CIE L*, a*, b* колорном систему. Боје одређене у влажном и сувом стању (помоћу Манселовог каталога боја) коришћене су за израчунавање вредности рубификације и меланизације, параметара који представљају саставни део индекса развоја земљишта. Као алтернативни показатељ црвенила земљишта (рубификације) и промене у садржају хематита, послужио је индекс црвенила земљишта. Вредновање/рангирањe црвенила земљишта извршено је за изразито рубификовано палеоземљиште V-S5 са профила Дукатар. Такође је извршено и мерење магнетног сусцептибилитета који има широку примену у лесно-палеоземљишним студијама као показатељ интензитета педогенезе. Резултати истраживања представљени у овој студији указују на значај локалитета Орловат, као кључног палеоклиматског и палеоеколошког архива горњег плеистоцена на простору Баната (северна Србија), односно југоисточног дела Карпатског (Панонског) басена. Са друге стране, резултати колориметријско-магнетних истраживања на локалитету Дукатар (V-S5) указују да је испитивано палеоземљиште формирано током периода MIS 13-15 (479-640 ka), који се карактерише вишим температурама током летњих месеци и/ или дужим сушним периодима. На основу палеопедолошких интерпретација, добијених колориметријских вредности и вредности индекса развоја земљишта изложених у овој студији, може се констатовати да испитиване лесно-палеоземљишне секвенце указују на сукцесију еколошких услова који се крећу од семи-хумидно суптропских окружења (V-S5) до типичних степских окружења (V-S1). Компарација са другим евроазијским лесно-палеоземљишним записима указује на присутност сличног палеоклиматског тренда. Резултати ове дисертације јасно апострофирају значај примене колориметријских метода у интердисциплинарном приступу приликом процене присутности феромагнетика и одређивања стенског магнетизма лесно-палеоземљишних секвенци средњег и горњег плеистоцена у средњем делу басена Дунава. Такође, овакав приступ значајан је приликом истраживања климатских и еколошких услова и успостављања корелација са другим локалитетима на регионалном нивоу.Lesno-paleozemljišne sekvence na prostoru Vojvodine (severna Srbija) predstavljaju najznačajnije regionalne paleoklimatske i paleoekološke arhive. Ispitivana sekvenca Orlovat- ciglana na Tamiškom, kao i Dukatar pedokompleks V-S5 na Titelskom lesnom platou izgrađeni su od sedimenata kvartarne starosti, formiranih tokom globalnih paleoklimatskih promena koje su se odigrale tokom gornjeg i srednjeg pleistocena. Promena boje između lesa i paleozemljišta predstavlja jedno od najvažnijih vizuelnih obeležja ovih litoloških članova. Takođe, navedene promene u bliskoj su vezi sa stepenom razvoja zemljišta. Najizraženije razlike u boji između lesa i paleozemljišta bazirane su na zastupljenosti dva feromagnetična minerala- hematita i getita. Pomenuti gvožđeviti minerali imaju značajnu zastupljenost u zemljištima i nosioci su zapisa o klimatskim i ekološkim promenama. Zemljišta koja sadrže samo, ili gotovo isključivo getit imaju žutu boju. Kada je prisutan hematit boja uglavnom postane crvenkasta, zbog činjenice da crveni hematit veoma uspešno maskira žuti getit. Detaljnim terenskim i laboratorijskim istraživanjima pomenutih lesno-paleozemljišnih sekvenci dobijene su kolorimetrijske vrednosti i vrednosti stenskog magnetizma prezentovane u okviru ove disertacije. Boja lesno-paleozemljišnih sedimenata u vlažnom i suvom stanju određena je primenom Manselovog kataloga boja zemljišta, a reflektivnost boja lesnih i paleozemljišnih uzoraka određena je instrumentalno, pomoću tristimulusnog kolorimetra. Kolorimetrijske vrednosti date su u CIE L*, a*, b* kolornom sistemu. Boje određene u vlažnom i suvom stanju (pomoću Manselovog kataloga boja) korišćene su za izračunavanje vrednosti rubifikacije i melanizacije, parametara koji predstavljaju sastavni deo indeksa razvoja zemljišta. Kao alternativni pokazatelj crvenila zemljišta (rubifikacije) i promene u sadržaju hematita, poslužio je indeks crvenila zemljišta. Vrednovanje/rangiranje crvenila zemljišta izvršeno je za izrazito rubifikovano paleozemljište V-S5 sa profila Dukatar. Takođe je izvršeno i merenje magnetnog susceptibiliteta koji ima široku primenu u lesno-paleozemljišnim studijama kao pokazatelj intenziteta pedogeneze. Rezultati istraživanja predstavljeni u ovoj studiji ukazuju na značaj lokaliteta Orlovat, kao ključnog paleoklimatskog i paleoekološkog arhiva gornjeg pleistocena na prostoru Banata (severna Srbija), odnosno jugoistočnog dela Karpatskog (Panonskog) basena. Sa druge strane, rezultati kolorimetrijsko-magnetnih istraživanja na lokalitetu Dukatar (V-S5) ukazuju da je ispitivano paleozemljište formirano tokom perioda MIS 13-15 (479-640 ka), koji se karakteriše višim temperaturama tokom letnjih meseci i/ ili dužim sušnim periodima. Na osnovu paleopedoloških interpretacija, dobijenih kolorimetrijskih vrednosti i vrednosti indeksa razvoja zemljišta izloženih u ovoj studiji, može se konstatovati da ispitivane lesno-paleozemljišne sekvence ukazuju na sukcesiju ekoloških uslova koji se kreću od semi-humidno suptropskih okruženja (V-S5) do tipičnih stepskih okruženja (V-S1). Komparacija sa drugim evroazijskim lesno-paleozemljišnim zapisima ukazuje na prisutnost sličnog paleoklimatskog trenda. Rezultati ove disertacije jasno apostrofiraju značaj primene kolorimetrijskih metoda u interdisciplinarnom pristupu prilikom procene prisutnosti feromagnetika i određivanja stenskog magnetizma lesno-paleozemljišnih sekvenci srednjeg i gornjeg pleistocena u srednjem delu basena Dunava. Takođe, ovakav pristup značajan je prilikom istraživanja klimatskih i ekoloških uslova i uspostavljanja korelacija sa drugim lokalitetima na regionalnom nivou.
Loess-palaeosol sequences in Vojvodina (North Serbia) represent a significant terrestrial sedimentary archives of climate and environmental changes during Pleistocene. The investigated sequence Orlovat on Tamiš, and Dukatar pedocomplex V-S5 on Titel loess plateau are comprised of quaternary sediments, formed due to global paleoclimatic changes during the Late and Middle Pleistocene. Loess and intercalated paleosols are characterized by significantly different colors. Obvious changes in hues can be interpreted as a consequence of different climate conditions under which pedocomplexes were formed. Goethite and hematite are the main iron oxides in loess and paleosols that strongly influence color differences. Presence of the above mentioned ferrimagnetica represent proxy of climatic and ecological changes. Soils containing only, or almost exclusively, goethite are yellow. When hematite is present, the color usually becomes reddish because the red hematite is very effective in masking the yellow goethite. Sampling and laboratory investigations of the mentioned loess-paleosol sections provided rock magnetic and colorimetric perspective on the Late and Middle Plistocene climate presented in this study. Wet colors were determined using a Munsell soil color chart. Dry colors were observed using the same Munsell soil color notation. Then, the dry samples were ground using mortar and pestle and color reflectance of loess and paleosol samples was determined colorimetrically using a chromameter. Color values as determined by the chromameter are given in the CIE L*, a*, b* color space. Wet and dry colors, determined by Munsell soil color chart were used for calculation of Rubification and Melanization Indices. The Rubification Index and Melanization Index represent common soil development indices. As an alternative proxy for soil reddening (rubification) and changes in the hematite content, the Redness Index was determined as well. The Redness Rating was calculated as average from moist and dry Munsell colors for strongly rubified pedocomplex V-S5 (Dukatar section). Rock magnetic measurements were carried out as well, since this parameter is generally applied as proxy for the exclusively pedogenetically formed fraction of ferrimagnetica (as shown in many loess-paleosol studies). The results presented in this study highlighted the importance of the Orlovat section as a key archive for the Late Pleistocene paleoclimate and paleoenvironment of the Banat region in Serbia, the southeastern part of the Carpathian (Pannonian) Basin. On the other hand, rock magnetic and colorimetric results of the Dukatar (V-S5) pedocomplex shows that investigated paleosol was formed during MIS 13-15 (479-640 ka), a period characterized by increase in summer temperature and/or duration of summer dryness. Due to paleopedological interpretations and measured colorimetric and soil development index values, it can be highlited that investigated loess-paleosol sequences presented in this study indicate a succession of interglacial environmental changes from semi-humid subtropical environments (V-S5) towards landscapes with typical steppe soils (V-S1). Comparison with equivalent Eurasian loess-paleosol records indicate a similar paleoclimatic trend. This study points out the potential of a joined colorimetric or spectrometric analyses and rock magnetic analyses in paleoenvironmental investigations on loess-paleosol sequences and correlation establishment between other sections on regional level.
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Melgar, Karlos Ernesto. "Improving the performance of soil-metal structures subjected to loss of soil support." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq30977.pdf.
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Yuan, Xu. "EVALUATION OF THE PHOSPHORUS LOSS ASSESSMENT TOOL (PLAT) AND REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) USING GEOSPATIAL INFORMATION." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-12212006-120809/.
Full textAbstract:
Excessive agricultural phosphorus (P) has been a major contributor to non-point source pollution. North Carolina developed the Phosphorus Loss Assessment Tool (PLAT) to evaluate the potential P loss from agricultural fields to waterbodies via four components. Our overall goal was to evaluate the potential of using spatial data to estimate P loss without physically visiting fields since many PLAT required parameters occur in spatial formats. The objective of the first study was to assess the possibility of spatial implementation of PLAT and to compare the effect of scale on the PLAT numerical results and the associated categorical rankings. Since an important input parameter, the average annual soil loss determined by the Revised Universal Soil Loss Equation, is not directly available from field measurement, our objective in the second study was to assess the potential of obtaining RUSLE estimates, specifically the topography factor LS, through Digital Elevation Model data in a Geographic Information System environment. In the first study, two methods of whole field average (WFA) and grid average (GA) were used to compare the difference in modeling P loss at different scales. The same list of PLAT required parameters were prepared from soil test reports and spatial database at the coarse scale of whole agriculture field and the fine scale of 0.4-ha grid. Soil tolerance value was used to temporarily replace the soil loss data. In the second study, a widely used Arc Macro Language (AML) program for estimating RUSLE topographic factor LS was evaluated through two approaches of whole field (WF) and representative profile (RP) analysis on a North Carolina landscape. Watershed delineation technique was adopted to select the representative profiles based on the references of slope distributions and field subdivisions from NRCS water quality specialists. Results from the first study indicated that soluble and particulate P loss, which occupied 59.3% and 26.3% of the total P loss through WFA method, and 56.1% and 39.0% through GA method, were the major pathways. Leaching P loss from PLAT was negligible. Particulate P loss was sensitive to scale as verified by the 12.7% increase of proportion in total P loss. The difference of particulate P loss through two methods was significant (p < 0.05), but no difference of soluble P loss and P source effect was found on a 95% confidence level. The overall P loss potential through two methods exhibited no significant difference due to the neutralization effect of individual pathways. Results from the second study showed that the AML program alone was not suitable for calculating RUSLE topographic factor on a North Carolina landscape because of the significant underestimation (~35% and ~20% through WF and RP approach, respectively). The concept of representative profile indeed improved the estimation accuracy (~15%), however, the linearity of the fitted line between field measured LS and GIS-aided LS estimate was not satisfactory. An adjustment factor was proposed rectifying the RUSLE-based AML program in order to approximate field measurements. This study demonstrated the potential of implementing PLAT model and the soil loss equation using spatial parameters derived from database instead of visiting the fields. The scale of modeling in estimating particulate P loss and RUSLE topographic factor LS was important and the adjustment factor was necessary to adapt the AML program application. The accuracy of model performance needed to be improved before claiming that GIS-aided PLAT modeling will provide a complete replacement for the field measurement.
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Saif, Hakeem Thamir. "Factors influencing base saturation and Ca/Mg ratios in soils of southeastern Ohio /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266362337536.
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Mare, Boussa Tockville <1979>. "Physical land degradation and loss of soil fertility: soil structural stability and bio-physical indicators." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6638/.
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This study investigates the changes in soil fertility due to the different aggregate breakdown mechanisms and it analyses their relationships in different soil-plant systems, using physical aggregates behavior and organic matter (OM) changes as indicators.
Three case studies were investigated: i) an organic agricultural soil, where a combined method, aimed to couple aggregate stability to nutrients loss, were tested; ii) a soil biosequence, where OM chemical characterisation and fractionation of aggregates on the basis of their physical behaviour were coupled and iii) a soils sequence in different phytoclimatic conditions, where isotopic C signature of separated aggregates was analysed.
In agricultural soils the proposed combined method allows to identify that the severity of aggregate breakdown affected the quantity of nutrients lost more than nutrients availability, and that P, K and Mg were the most susceptible elements to water abrasion, while C and N were mainly susceptible to wetting.
In the studied Chestnut-Douglas fir biosequence, OM chemical properties affected the relative importance of OM direct and indirect mechanisms (i.e., organic and organic-metallic cements, respectively) involved in aggregate stability and nutrient losses: under Douglas fir, high presence of carboxylate groups enhanced OM-metal interactions and stabilised aggregates; whereas under Chestnut, OM directly acted and fresh, more C-rich OM was preserved. OM direct mechanism seemed to be more efficient in C preservation in aggregates.
The 13C natural abundance approach showed that, according to phytoclimatic conditions, stable macroaggregates can form both around partially decomposed OM and by organic-mineral interactions. In topsoils, aggregate resistance enhanced 13C-rich OM preservation, but in subsoils C preservation was due to other mechanisms, likely OM-mineral interactions.
The proposed combined approach seems to be useful in the understanding of C and nutrients fate relates to water stresses, and in future research it could provide new insights into the complexity of soil biophysical processes.
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Dibben, Susan. "A microstructural model for collapsing soils." Thesis, Nottingham Trent University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266820.
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Tecle, A., D. P. Dykstra, W. W. Covington, and L. D. Garrett. "Proposed Methodology for Soil Loss Prediction from Southwestern Forest." Arizona-Nevada Academy of Science, 1990. http://hdl.handle.net/10150/296446.
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From the Proceedings of the 1990 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 21, 1990, Arizona State University, Tempe, Arizona
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Son, Vo Thanh, and n/a. "Evaluation of the USLE (Universal Soil Loss Equation) to estimate soil loss from hobby farms and commercial pastoral properties around Murrumbateman, NSW, Australia." University of Canberra. Applied Science, 1993. http://erl.canberra.edu.au./public/adt-AUC20061108.171337.
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This thesis is an evaluation of the use the USLE to estimate soil loss from
two pastoral land uses - commercial properties and "hobby farms" in
Murrumbateman. Sensitivity analysis was used to evaluate the USLE
components. Sediment measurement in farm dams was taken to estimate
sediment yield from several sites, as an alternative approach to study soil
loss. The annual soil loss from entire study area was 0.25 t/ha/year whilst
these figures from commercial properties and hobby farms were 0.29
t/ha/year and 0.21 t/ha/year, respectively. The annual average sediment
yield from three catchments in hobby farms was 0.3 t/ha/year. The USLE
was found to be highly sensitive to slope steepness, ground cover and
stocking rates. The critical values were 16% for slopes, 35% for the ground
cover and 19 Dry Sheep Equivalent/ha for stocking rate. I tentatively
conclude that the USLE is sufficiently sensitive to detect differences in soil
loss between the two land uses. There is, however, a need to improve the
operation of the model in some respects. The use of farm dams for
estimating sediment yield also shows promise.
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Nguyen, Gia Huynh Truong. "Evaluating soil erodibility parameters with mini-JET under various soil moisture conditions." Kansas State University, 2016. http://hdl.handle.net/2097/34526.
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Master of ScienceDepartment of Biological & Agricultural Engineering
Aleksey Y. Sheshukov
Soil erosion is one of the main reasons for agricultural land degradation in the world. Losses of land because of high soil erosion rates and rapidly expanding population result in significant reduction of cultivated land area per capita, and shortage of food on the global scale. Soil erosion can be a major source of sediment in the aquatic systems leading to reduction of organism population and poor water quality. Many factors affect soil erodibility, such as, soil properties, rainfall, topographic features, land use, and management practices, among others. The impacts of soil moisture content, however, are not well understood and. therefore, the primary goal of this study was to quantify two soil erodibility parameters, the erodibility coefficient and critical shear stress, under different soil moisture conditions using the jet erosion test (JET). The JET test uses the apparatus (called mini-JET) that creates an impinging jet of water into the soil and records the resulting scour depth over time. The scour depth time series are then fitted into a non-linear soil erosion equation, yielding the sought values of erodibility parameters. For this study, more than 40 soil samples were collected from several sites in Kansas, processed, and prepared to conduct JET tests in the lab setting. The effects of tillage and soil moisture content were of interest to this study. The results showed varied effects of soil type and sample soil moisture condition on the scour depth development and parameters sensitivity. The critical shear stress decreased and the erodibility coefficient increased with the increase of initial moisture content for clay loam soil, while critical shear stress did not change for sandy loam soil. The study also revealed higher erosive properties of soil collected from the tilled field compared to the no-till field.
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Baker, Malchus B. Jr, and Leonard F. DeBano. "Runoff and Soil Loss from Selected Rangeland Sites in California." Arizona-Nevada Academy of Science, 2000. http://hdl.handle.net/10150/296556.
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Garcia-Chevesich, Pablo A., Peter F. Ffolliott, and Daniel G. Neary. "Soil Loss Following the Rodeo-Chediski Wildfire: An Initial Assessment." Arizona-Nevada Academy of Science, 2004. http://hdl.handle.net/10150/296632.
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Kelly, Darren. "Effect of particle loss on soil volume, strength and stiffness." Thesis, Edinburgh Napier University, 2015. http://researchrepository.napier.ac.uk/Output/8865.
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Soil particle loss can occur through biodegradation, erosion and dissolution. Yet there is little understanding of the mechanical changes that accompany these phenomena, especially where the size of particle removed is concerned. This study investigated the influence of particle loss on the volumetric, strength and small strain stiffness of analogue soils. These consisted of uniform Leighton Buzzard sand with selected salt particle sizes. Particle sizes chosen for experimental tests are representative of the fines that might be lost through an erosion process called suffusion in embankment dams or the various sizes that might be degraded and/or decomposed in landfill and mining wastes. A triaxial apparatus was modified to allow the in-situ dissolution of samples under triaxial stress states. This was achieved through the circulation of water through the pore-water pressure line with ow controlled by differential pressure using a peristaltic pump. Bender elements were installed to monitor changes in shear wave velocity before, during and after dissolution. Test results showed increases in void ratio in all dissolution tests. The influence of salt size and the stress under which tests were performed was found to have a limited impact on the magnitude of void ratio increase. Salt particle size did, however, affect the initial packing density of the sand-salt mixtures with fine salt sizes resulting in lower void ratios. Therefore, these tests showed lower post-dissolution void ratios. Coarse salt sizes initially densely prepared resulted in high post-dissolution void ratios close to the maximum void ratio for the Leighton Buzzard sand. Ultimately, post-dissolution void ratios determined the large-strain shearing behaviour. Therefore the fine salt tests, in which the post-dissolution void ratios were lowest, were the only tests to show minor peak strengths prior to the critical state with a shear behaviour described as strain-softening dilative. The comparatively high void ratios obtained in coarse salt tests showed no peak strength but a strain-hardening contractive behaviour. The structural role of salt particles within sand mixtures was continually assessed with evidence suggesting that salt particles maintainedtheir structural integrity under the stresses applied through loading and subsequent shearing in this study. The influence of particle loss on the critical state was also probed. Post-dissolution samples consistently showed higher critical void ratios than sand-only samples not subjected to particle loss. Most of the findings might be explained in the context of strong force chains and their stability which is in turn influenced by the amount and size of soluble particles. Shear wave velocities were shown to decrease significantly with dissolution of 15% of weight of salt irrespective of size. Associated small-strain stiffness moduli were found to decrease even more substantially. The reported changes illustrate the significant influence that particle removal has on the mechanical properties of soil and are discussed and analysedwithin this thesis.
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Dell'Olio, Laura Ashley. "Refining the Phosphorus Loss Assessment Tool for the Organic Soils of North Carolina." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-10262006-141107/.
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Phosphorus (P) runoff and leaching from agricultural fields have been identified as major environmental concerns for the health of aquatic ecosystems. North Carolina has responded by implementing the Phosphorus Loss Assessment Tool (PLAT). The goal of the PLAT is to determine relative P losses from agricultural fields based on several site factors and characteristics, including Mehlich-3 P (M3P) soil test values. Based on previous research, the current version of PLAT is programmed to predict greater soluble P losses from organic soils than from mineral soils with the same M3P values. However, recent research specific to North Carolina?s organic soils has indicated decreased soluble P release in the presence of high Al concentrations. Our objectives were to determine (i) the Al content of Typic Haplosaprists and Terric Haplosaprists of North Carolina?s Lower Coastal Plain, and (ii) how the Al in these soils affects P retention. We sampled four organic soil series and determined M3P, Mehlich-3 Al (M3Al), Mehlich-3 Fe (M3Fe), water-soluble P (WSP), total P, pH, particle size distribution, and the organic matter content (OM). Water-soluble P and M3P were also measured in a 21-d incubation study in which P was added at a rate equivalent to 150 kg P ha-1. Total CuCl2 extractable Al and inorganic soil P fractions were identified in an Al and inorganic P fractionation study, respectively. According to the results of the incubation, multiple regression, and fractionation studies, Al was the main cation responsible for P retention; the mean topsoil M3Al concentrations (1926 mg kg-1) in these organic soils were much higher than those observed in another study of mostly mineral NC soils. The concentration of M3Fe was low in every series and was not correlated to any P characteristics. Mehlich-3 P was not consistently correlated to P retention and WSP; however, OM, M3Al, and total CuCl2 extractable Al were correlated with P retention. In the incubation study, the percentage of applied P that was adsorbed was greater in soils with lower OM and/or higher M3Al. Increased OM was associated with increased WSP and lower total P, as well as decreased P retention. The opposite effect was observed with increasing M3Al concentrations; however, the ratio of OM to M3Al showed increased correlation to P retention and WSP than when OM and Al were used alone. These results indicate that soils with higher OM and lower Al did not retain P as well as soils with lower OM and higher Al contents. Furthermore, as more Al bound P was extracted by M3P (causing higher M3P/Al-P %), WSP increased, and coincided with decreased total CuCl2 Al. The results from this study show that in high OM soils, the concentration of extractable Al controlled the solubility of P. North Carolina?s PLAT could be modified to include M3Al concentrations to more accurately predict P losses in the organic soils of the lower coastal plain, thus potentially reducing P runoff and leaching into our aquatic ecosystems.
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Bellett-Travers, David Marcus. "Water relations and soil moisture requirements of transplanted amenity trees during establishment." Thesis, University of Hertfordshire, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251544.
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Marr, Paul Gerard. "Approximating soil loss calculations with satellite data and multivariate regression analyses." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc798418/.
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Digital satellite remote sensing and Geographic Information Systems (GIS) have been used effectively to determine the Universal Soil Loss Equation (USLE) output for a number of North Texas watersheds. This method involves determining the values of each of the USLE factors and using these factors as information layers within the GIS.
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Mulengera, Matthew Kagorobha. "Soil loss prediction in the semi-arid tropical savanna zone : a tool for soil conservation planning in Tanzania." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318175.
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Bhattacharyya, Ranjan. "Using palm-mat geotextiles for soil conservation on arable loamy sands in the United Kingdom." Thesis, University of Wolverhampton, 2009. http://hdl.handle.net/2436/88536.
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To date, most studies on the effectiveness of geotextiles on soil erosion rates were conducted in laboratory experiments for <1 h. Hence, at Hilton, East Shropshire, UK, this study investigated the effectiveness of palm-mat geotextiles (Borassus and Buriti mats) in reducing rainsplash erosion, runoff and soil loss and changing selected soil properties under field conditions over two years (January 2007-January 2009). Mat-cover effects on rainsplash erosion were studied in two sets on a loamy sand soil (0o slope). In both sets, six randomly-selected plots (each 1 m2) were completely matcovered and six were bare. Unlike Buriti mats, Borassus mat-cover on bare soil significantly (P<0.001) decreased rainsplash erosion (by ~89%). Duplicate runoff plots (10 x 1 m on a 15o slope) had five treatments (bare, permanent grass, Borassus completely-cover, Borassus buffer strip and Buriti buffer strip). Using Borassus buffer strips (area coverage ~10%) on bare soil decreased runoff by ~71% (P>0.05) and soil erosion by ~92% (P<0.001). Borassus buffer strip, Buriti buffer strip and Borassus completely-covered plots had similar effects in decreasing runoff and soil loss. However, the longevity of Borassus mats was ~twice that of Buriti mats. Despite physical protection, runoff control and sediment entrapment, biomat buffer zones may considerably alter and protect flow direction by presenting barriers and creating several cross-drains. Except Borassus completely-covered plots, all plots had significant (P<0.05) increases in topsoil (0-5 cm) bulk density and decreased aggregate stability. However, buffer strips were more effective in trapping fine particles than Borassus completely-covered plots. No treatments had significant (P>0.05) effects on changes in pH, soil organic matter, total soil carbon or N. Plots with Borassus mats significantly (P<0.05) increased total P and decreased total Ca. Treatments had no significant effects on changes in total S, Mg, Zn, Cu, Fe, Mn, Mo or Cl concentrations. Borassus buffer strips can effectively conserve soil and water and improve and maintain selected soil properties, with results similar to Borassus completely-covered plots. The mechanisms explaining the effectiveness of buffer zones require further studies under varied pedo-climatic conditions.
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Tarkalson, David Dale. "PHOSPHORUS LOSS IN SURFACE RUNOFF FROM PIEDMONT SOILS RECEIVING ANIMAL MANURE AND FERTILIZER ADDITIONS." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010926-002603.
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The purpose of this research was to measure P losses in runoff from agricultural land in the Piedmont region of the southeastern U.S. with varying soil P levels and receiving broiler litter and inorganic P fertilizers. The experimental results will be helpful for the development of the P Loss Assessment Tool in North Carolina and other P Index approaches in states with similar soil characteristics and crop management practices. A net influx of P into many areas due to high animal populations has resulted in increased potential P losses to sensitive surface waters. A typical North Carolina broiler farm and dairy farm were found to have annual P surpluses of 65 kg P/ha and 20 kg P/ha respectively. The use of low phytic acid corn varieties and phytase enzyme has the potential to reduce the P surplus on broiler farms by 25 to 58%. Phosphorus losses in runoff from Piedmont conventional till (CT) and no-till (NT) soils with varying soil P concentrations and from soils currently receiving broiler litter and fertilizer P applications were assessed. In these studies, rainfall simulation at rates of 6 and 7.6 cm/hr were utilized to collect runoff samples from crop land with a range of initial P concentrations and from plots with varying fertilizer P and broiler litter application rates, both incorporated and broadcast. Runoff samples were collected at 5-min intervals for 30 min and analyzed for reactive P (RP), algal-available (AAP), and total P (TP). Concentration of RP in runoff from CT and NT plots was positively correlated with Mehlich-3 extractable P (r2 = 0.61 and 0.7 respectively) and oxalate extractable degree of P saturation (DPS) (r2 = 0.6 and 0.61 respectively). However, only TP mass loss (kg TP/ha) in runoff from CT was correlated with DPS (r2 = 0.57). A Mehlich 3 extractable P concentration of 350 mg P/kg and a DPS of 84% corresponded to 1 mg RP/L in runoff. Incorporation of broiler litter and inorganic P fertilizer into the soil at all P application rates virtually eliminated P runoff loses and had similar P losses in runoff as the unfertilized control. Surface application of broiler litter resulted in runoff containing between 2.9 and 24.5 mg RP/L for application rates of 8 to 82 kg P/ha respectively. Mass loss of TP in runoff from surface-applied broiler litter ranged from 1.3 to 8.5 kg P/ha over the same application rates. There was no significant relationship between surface applied inorganic P application rate and RP concentrations or TP mass losses in runoff. However, there was a trend for increased RP concentrations and TP mass losses in runoff with increasing application rate. Concentration of RP and mass loss of TP in runoff from surface applied inorganic P averaged 4.9 mg RP/L and 1.1 kg P/ha over all application rates. There was no significant difference between P losses in runoff from plots receiving surface applied conventional broiler litter and broiler litter derived from birds fed a low phytic acid corn (High Available P corn).
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Bobe, Bedadi Woreka. "Evaluation of soil erosion in the Harerge region of Ethiopia using soil loss models, rainfall simulation and field trails." Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-08022004-141533.
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Bobe, Bedadi Woreka. "Evaluation of soil erosion in the Harerge region of Ethiopia using soil loss models, rainfall simulation and field trials." Thesis, University of Pretoria, 2004. http://hdl.handle.net/2263/26929.
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Accelerated soil erosion is one of the major threats to agricultural production in Ethiopia and the Harerge region is not exceptional. It is estimated that about 1.5 billion tones of soil is being eroded every year in Ethiopia. In the extreme cases, especially for the highlands, the rate of soil loss is estimated to reach up to 300 t ha-1yr-1 with an average of about 70 t ha -1yr-1 which is beyond any tolerable level. The government have made different attempts to avert the situation since 1975 through initiation of a massive program of soil conservation and rehabilitation of severely degraded lands. Despite considerable efforts, the achievements were far bellow expectations. This study was aimed at assessing the effect of some soil properties, rainfall intensity and slope gradients on surface sealing, soil erodibility, runoff and soil loss from selected sites in the Harerge region, eastern Ethiopia, using simulated rainfall. Soil loss was also estimated for the sites using Soil Loss Estimation Model for Southern Africa (SLEMSA) and the Universal soil Loss Equation (USLE). Moreover, the effectiveness of various rates and patterns of wheat residue mulching in controlling soil loss was also evaluated for one of the study sites, (i.e. Regosol of Alemaya University), under both rainfall simulation and field natural rainfall conditions. For most of the erosion parameters, the interaction among soil texture, slope gradient and rainfall intensity was significant. In general however, high rainfall intensity induced high runoff, sediment yield and splash. The effect of slope gradients on most of the erosion parameters was not significant as the slope length was too small to bring about a concentrated flow. The effect of soils dominated by any one of the three soil separates on the erosion parameters was largely dependent on rainfall intensity and slope gradient. The soils form the 15 different sites in Harerge showed different degrees of vulnerability to surface sealing, runoff and sediment yield. These differences were associated with various soil properties. Correlation of soil properties to the erosion parameters revealed that aggregate stability was the main factor that determined the susceptibility of soils to sealing, runoff and soil loss. This was in turn affected by organic carbon content, percent clay and exchangeable sodium percentage (ESP). Soils with relatively high ESP such as those at Babile (13.85) and Gelemso (7.18) were among the lowest in their aggregate stability (percent water stable aggregates of 0.25 –2.0mm diameter); and have highest runoff and sediment yield as compared to other soils in the study. Similarly, most of those soils with relatively low ESP, high organic carbon content (OC%) and high water stable aggregates such as Hamaressa, AU (Alemaya University) vertisol and AU regosol were among the least susceptible to sealing and interrill erosion. Nevertheless, some exceptions include soils like those of Hirna where high runoff was recorded whilst having relatively high OC%, low ESP and high water stable aggregates. Both the SLEMSA and USLE models were able to identify the erosion hazards for the study sites. Despite the differences in the procedures of the two models, significant correlation (r = 0.87) was observed between the values estimated by the two methods. Both models estimated higher soil loss for Gelemso, Babile, Karamara and Hamaressa. Soil loss was lower for Diredawa, AU-vertisol and AU-Alluvial all of which occur on a relatively low slope gradients. The high soil loss for Babile and Gelemso conforms with the relative soil erodibility values obtained under rainfall simulation suggesting that soil erodibility, among others, is the main factor contributing to high soil loss for these soils. The difference in the estimated soil losses for the different sites was a function of the interaction of the various factors involved. Though the laboratory soil erodibility values were low to medium for Hamaressa and Karamara, the estimated soil loss was higher owing to the field topographic situations such as high slope gradient. SLEMSA and USLE showed different degrees of sensitivities to their input variables for the conditions of the study sites. SLEMSA was highly sensitive to changes in rainfall kinetic energy (E) and soil erodibility (F) and less sensitive to the cover and slope length factors. The sensitivity of SLEMSA to changes in the cover factor was higher for areas having initially smaller percentage rainfall interception values. On the other hand, USLE was highly sensitive to slope gradient and less so to slope length as compared to the other input factors. The study on the various rates and application patterns of wheat residue on runoff and soil loss both in the laboratory rainfall simulation and under field natural rainfall conditions revealed that surface application of crop residue is more effective in reducing soil loss and runoff than incorporating the same amount of the residue into the soil. Likewise, for a particular residue application method, runoff and soil loss decreased with increasing application rate of the mulch. However, the difference was not significant between 4 Mg ha-1 and 8 Mg ha-1 wheat straw rates suggesting that the former can effectively control soil loss and can be used in areas where there is limitation of crop residues provided that other conditions are similar to that of the study site (AU Regosols). The effectiveness of lower rates of straw (i.e. less than 4 Mg ha-1 ) should also be studied. It should however be noted that the effectiveness of mulching in controlling soils loss and runoff could be different under various slope gradients, rainfall characteristics and cover types that were not covered in this study. Integrated soil and water conservation research is required to develop a comprehensive database for modelling various soil erosion parameters. Further research is therefore required on the effect of soil properties (with special emphasis to aggregate stability, clay mineralogy, exchangeable cations, soil texture and organic matter), types and rates of crop residues, cropping and tillage systems, mechanical and biological soil conservation measures on soil erosion and its conservation for a better estimation of the actual soil loss in the study sites. Copyright 2004, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bobe, BW 2004, Evaluation of soil erosion in the Harerge region of Ethiopia using soil loss models, rainfall simulation and field trials, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-08022004-141533 / >Thesis (PhD (Soil Science))--University of Pretoria, 2004.
Plant Production and Soil Science
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Williams, Nekesha Bernadette. "Linking Soil Loss to Sediment Delivery in Two Estuaries in Puerto Rico." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3504.
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Enhanced soil loss from the watershed is a major environmental issue. Increased soil loss from a watershed can potentially increase sediment delivery and loading to aquatic ecosystems such as rivers and estuaries. An increase in sediment delivery and loading to freshwater and transitional marine ecosystems can impact water quality and supply specifically by: (1) reducing water clarity, (2) transporting nutrient and pollutant laden sediments and (3) reducing the storage capacity of reservoirs. To address these broader environmental impacts of increased sediment delivery and loading to aquatic ecosystems it is imperative that potential source areas of sediments available for transport are identified in the watershed. It is also important that sediment source areas are linked to sediment transport and delivery to aquatic ecosystems.
This study attempted to establish a link between soil loss from watersheds and sediment delivery in two estuaries on the island of Puerto Rico. The two estuarine systems used in this investigation were the Rio Espiritu Santo (RES) riverine-estuarine system and the Jobos Bay (JB) Estuary. Soil loss from both study watersheds was estimated using RUSLE. Sediment cores and surface grab samples were collected from both estuaries. In addition, soil samples were collected from the two watersheds. Gamma analyses were performed in order to measure activity concentrations of 137Cs and excess 210Pb in sediment cores, surface and soil samples. 137Cs inventories were computed for each core collected from both watersheds. Also, grain-size and LOI were performed on the sediments to describe the sedimentological characteristics of collected sediment cores, surface samples and soil samples.
A conceptual framework was developed and implemented for linking sediment production, availability (supply), transport and delivery to study estuaries. Results from the RUSLE model indicated that soil loss within both watersheds were low with patchy instances of erosional hotspots. These results did not provide any information on sediment supply or insights into the hydrologic connectivity of the study watersheds. 137Cs inventories computed from the RES watershed indicated that sediment cores located further upstream had the highest inventories. With reference to the JB Estuary, statistical analysis showed that location had an effect on distribution of Cs in surface samples within the bay. Sedimentological characteristics varied between cores.
The implementation of the conceptual model in both study watersheds allowed for the identification of potential source areas of sediments that were available for transport and delivery to adjacent aquatic systems. This investigation revealed that to link soil loss to sediment delivery it is essential that key processes and variables (rainfall, soils, LULC and geomorphology) must be included in the analysis. This conceptual model may be a valuable tool for monitoring and managing soil loss within the watershed and consequently, addressing problems of increased sediment delivery to aquatic and transitional marine ecosystems such as estuaries.
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Chappell, Adrian. "Geostatistical mapping and ordination analyses of '1'3'7CS-derived net soil flux in south-west Niger." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327548.
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Huang, Yuh-Ming. "The effects of precipitation of calcium carbonate on soil pH following urea application." Thesis, University of Oxford, 1990. https://ora.ox.ac.uk/objects/uuid:a81844cb-c0c1-4dd3-a3c5-fc7a1b716021.
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This thesis describes a series of experiments both in solution systems and soil systems to study the precipitation of calcium carbonate in soils and the effects of the precipitation on soil pH after urea had been applied. (1) A gas bubbling system has been established which introduces ammonia at a steady rate to the reaction solution and keeps it equilibrated at 0.00484 atm partial pressure of carbon dioxide. (2) In a non-seeded system, the effects of calcium, urea, Mg (magnesium), P (phosphate), and DOC (water-dissolved organic matter) on the precipitation were examined individually and in various combinations. Calcite and vaterite were found in the 10 mM CaC12 solutions with and without the addition of urea. When the solutions contained Mg, P, and DOC, vaterite was not found. Aragonite was found in the reaction solution containing 5 mM Mg. In high initial concentration of P (5x10-4 M) , the formation of calcium phosphate (amorphous by X-ray analysis) catalysed the formation of calcite. The effects of urea and Mg on the precipitation are negligible compared with the effects of P and DOC. (3) In a seeded system, 16 sets of experiments with four sizes of calcite-seeds were carried out to study the precipitation rate of calcium carbonate. This was described by the equation LR=-4.113±0.132 + 0.379±0.029 LWA + LSI where LR=log (precipitation rate, PR, in mole litre-1 min-1), LWA= log (newly formed calcium carbonate, g ml-1), and LSI=log (degree of supersaturation of calcium carbonate, SI). (4) A wide range of concentrations of urea (0.05, 0.1, 0.3, 0.5, 0.7, and 1 M) were added to three soils (Beg., Uni., and VWH) with or without the addition of 5 per cent of calcite (10-15 μm) to establish a rate model for the precipitation of calcium carbonate in soils. The precipitation model (in logarithmic form) in soils is lnPR=-9.47±0.30 + lnKSOIL + 0.379±0.029 InWA + InSI - 1686±703 P - 6.13±3.02 DOC + 3854±1775 (P DOC) where P and DOC are the concentrations in soil solutions, and lnKSOIL is the effect of soils on the precipitation, which is - 1.98, 0.43, and -0.10 for Beg., Uni., and VWH soils respectively. The amount of newly formed calcium carbonate is about a third to a half of the amount of ammoniacal-N released by urea hydrolysis. It was able to reduce the increase of soil pH by more than 0.6 pH units in some circumstances.
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Sourlamtas, Konstantinos. "Soil Erosion estimation for the Göta Älv river using remote sensing, GIS and the Revised Universal Soil Loss Equation (RUSLE) model." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-175412.
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According to previous studies, the study area of Göta Älv river has high risk of landslides along the river banks due to the water flow. Soil erosion can affect the increase of the landslides in an area with unstable soils caused by the increase rainfall. The Swedish climate is getting more vulnerable thus there is a potential increased risk in erosion and landslides due to unpredictable rainfall intensity. This study aims to calculate soil erosion for the Göta Älv river using the Revised Universal Soil Loss Equation (RUSLE) where a comparison of data from remote sensing and meteorological and geological agencies were completed. Two research questions will be addressed, first if the different calculation of the soil erodibility (K) factor affects RUSLE result, and second how much soil erosion occurs and will potentially occur in the future. Factors including rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), land cover management (C) and conservation practices (P) were analyzed and used as inputs for the RUSLE model. Moreover, three scenarios were applied for the calculation of K factor in order to show how each one can affect the soil erosion result. The scenarios includes the K-scenario 1, 2 and 3, where the values were derived from a world soil database, a table with literature values and estimated field measurements, respectively. Also, three scenarios for R factor were applied for the periods 2000-2018, 2021-2050 and 2069-2098 (R-scenarios 1, 2 and 3) in order to show how future changes to rainfall patterns could affect soil erosion in the Göta Älv river and if it increases the risk of the landslides. The results suggest that the soil erosion varied between 0 – 0.5 t/ha for all the time periods with mean annual soil loss between 20 – 22 t/ha/yr and maximum soil loss between 2158- 5443 t/ha. The difference between the three K factor scenarios is almost 4%, which is pretty low thus, no influence on the soil erosion results. In conclusion, the different calculations of the K factor affected more the estimated maximum soil loss instead of the mean annual soil loss. The different calculations of R factor showed that more than 90% of the total area was not affected by the soil erosion when the soil loss will not be increased considerably in the future due to the rainfall increase.
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Young, Michael Howard 1961. "Monitoring near-surface soil water loss with time domain reflectometry and weighing lysimeters." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/191191.
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Three goals of this research were: 1) to develop a field-scale research facility that could be used for conducting a variety of soil water experiments in both deep (greater than 2 meters) and near-surface soils where the soil water balance could be accurately determined; 2) to develop a transient experimental technique for calibrating time domain reflectometry (TDR) probes; and 3) to study the use of vertically-installed TDR probes for measuring near-surface soil water movement in a field setting, and to compare these measurements with those made by the weighing lysimeter. The weighing lysimeter facility consists of two lysimeter tanks, 4.0 m deep and 2.5 m in diameter, which rest atop a scale with a resolution of ±200 g, equivalent to ±0.04 mm of water on the surface. Data collection is completely automated with a data logger and personal computer. Both lysimeters are instrumented with TDR probes, tensiometers, and pore water solution samplers; thermocouples are installed in one lysimeter for measuring temperature. The TDR probes were calibrated using a transient method known as upward infiltration. The method is rapid, allows the soil to remain unchanged during the experiment, and provides many data points. The upward infiltration method was tested using two different length probes in soils of three textures. Results show that the upward infiltration method is stable, repeatable, and provides accurate dielectric constants and calibration curves. Four, vertically-installed TDR probes of different lengths (200, 400, 600, and 800 mm) were placed in the lysimeter at ground surface to measure water added and water lost during a one-month period in the presence of daily irrigated turfgrass. The purpose of this study was to compare changes in soil water storage as measured by the TDR system, against measurements made using the weighing lysimeter. The TDR probes detected diurnal changes in water content due to irrigation and evapotranspiration, even when these amounts changed slightly from day to day. The TDR probes underestimated the measurements of both water added and water loss, as confirmed using measurements from the weighing lysimeter. The presence of a 47-mm thick biomass above the TDR waveguides retained water that otherwise would have percolated the soil surface into the measurement domain of the probes. Addition and loss of water in the biomass were recorded by the lysimeter, but not by the TDR probes, thus explaining the underestimation. Modeling of near-surface water movement with the HYDRUS model showed very similar water movement behavior as measured by the TDR probes. This confirms our hypothesis that TDR would a useful tool for measuring diurnal changes in water content for irrigation scheduling.
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Flack, Paul E. 1960. "A method for establishing base-line soil loss rates on surface mine sites." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276985.
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Surface mining operations require a comparison of post-mining erosion rates with pre-mining soil loss to ascertain if remedial measures are needed. In this study the Universal Soil-Loss Equation (USLE) was modified to reflect conditions of western rangelands to develop a procedure for estimating pre-mining soil loss rates. The modification used back-calculation for the C-Factor and an adjusted R-Factor based on storm size. Soil loss simulation based on stochastic precipitation patterns is appropriate to the site--the La Plata mine area in northern New Mexico--and increases the flexibility of the USLE as a soil loss predictor for western rangelands.
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Samba, Idrissa. "Simulation of rainfall, runoff, peakflow and soil loss in the upper Gambia River Basin." Thesis, The University of Arizona, 1986. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0324_sip1_w.pdf&type=application/pdf.
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Rapp, John Francis 1963. "Error assessment of the revised universal soil loss equation using natural runoff plot data." Thesis, The University of Arizona, 1994. http://hdl.handle.net/10150/291699.
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The error associated with the Revised Universal Soil Loss Equation (RUSLE) was determined by utilizing data from 21 U.S. sites representing 1704 years of measurements from 206 plots. RUSLE estimates were compared to the measured values for each year and the average value for each plot duration. The model efficiency coefficient on an annual basis was (.58) and on an average annual basis was (.73). The RUSLE was consistent with a previous study of the USLE which tended to over predict on plots with low erosion rates and under predict on plots with high erosion rates. Also the Topographic Factor (LS) value and the Cover and Management Factor (C) value had the most influence on model efficiency. The basis for this study was to compare the RUSLE with the USLE and to compare RUSLE simulations with observed data that was not a part of its critical development.
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Ping, Zhang. "The partitioning of water loss between crop transpiration and soil evaporation in potato crops." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303926.
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Rife, Trixie. "Modeling the Value of Ecosystem Services: Application to Soil Loss in Southeastern Allegheny County." Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1289949795.
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Totolo, Otlogetswe. "The use of a geographic information system GIS(SPANS) to facilitate detailed evaluation of soil and land." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309532.
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