• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1103
  • 351
  • 333
  • 127
  • 88
  • 64
  • 46
  • 32
  • 24
  • 20
  • 12
  • 12
  • 11
  • 9
  • 8
  • Tagged with
  • 2811
  • 330
  • 278
  • 246
  • 235
  • 222
  • 188
  • 173
  • 169
  • 144
  • 127
  • 124
  • 122
  • 122
  • 121
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

The Influence of Deep-Seated Landslides on Topographic Variability and Salmon Habitat in the Oregon Coast Range, USA

Beeson, Helen 29 September 2014 (has links)
A well-accepted idea in geomorphology is that landforms control the type and distribution of biological habitat. However, the linkages between geomorphology and ecology remain poorly understood. In rivers, the geomorphic template controls the hydraulic environment, partly shaping the river ecosystem. But what processes shape the geomorphic template? Here, I examine how two hillslope processes dominant in the Oregon Coast Range, debris flows and deep-seated landslides, affect valley floor width and channel slope, key components of the geomorphic template in riverine ecosystems. I then investigate how patterns in potential salmon habitat differ between streams dominated by deep-seated landslides and streams dominated by debris flows. I show that terrain influenced by deep-seated landslides exhibits (1) valley widths that are more variable throughout the network but less locally variable, (2) more variable channel slopes, and (3) more potential salmon habitat as well as significantly more connectivity between habitat types.
242

Influência de períodos de pastejo em trigo duplo propósito sobre a decomposição e liberação de nutrientes da palhada em sistema de integração lavoura-pecuária

Bortolli, Marcos Antonio de January 2010 (has links)
CAPES / Os objetivos deste trabalho foram avaliar a influencia de períodos de pastejo em trigo duplo propósito sobre a taxa de decomposição das plantas e liberação de nutrientes (N, P, K, Ca e Mg) bem como a produtividade de soja cultivada na sequencia em sistema de semeadura direta. Os tratamentos foram arranjados em delineamento blocos ao acaso com duas repetições. Os tratamentos foram os seis períodos de pastejo (0, 21, 42, 63, 84 e 105 dias) e a taxa de decomposição do material residual destes, foi avaliada pela técnica de litter-bag. A percentagem de biomassa e nutrientes no compartimento mais prontamente decomponível aumentou à medida que aumentou os períodos de pastejo, principalmente devido ao efeito do animal sobre a renovação dos tecidos foliares, o que resultou em uma maior taxa de decomposição da palhada e de liberação de nutrientes para o solo e, consequentemente para a cultura da soja cultivada na sequencia em sistema de integração lavoura pecuária. Entretanto a produtividade de grãos de soja reduziu com o aumento dos períodos de pastejo principalmente devido à diminuição de resíduo de matéria seca sobre o solo. / The aims of this work were to evaluate the influence of dual purpose wheat grazing periods on plant decomposition rates and nutrient release (N, P, K, Ca e Mg) and soybean yielded cultivate in sequence in no-till systems. Treatments were laid out as a random block design with two replications. The treatments were six grazing periods (0, 21, 42, 63, 84 e 105 days), on continuous stocking rate grazing method. From these treatments, dual purpose wheat biomass and nutrients decay constants were evaluated along 7 different field incubation periods (0, 15, 35, 63, 98, 139 e 196 days after soil deposition) by the litter bag technique. The percentage of biomass and nutrients at the easily decomposable compartment increases with the increase of grazing periods, due to the influence of the animal over the plants tissue turnover, which results in highest decomposition rate and nutrients release to the soil and consequently to the soybean cultivated in sequence on crop-livestock system. However the soybean grains yielded reduced with the increase grazing periods mainly due to the diminished of dry matter residue over the soil.
243

Influência de períodos de pastejo em trigo duplo propósito sobre a decomposição e liberação de nutrientes da palhada em sistema de integração lavoura-pecuária

Bortolli, Marcos Antonio de January 2010 (has links)
CAPES / Os objetivos deste trabalho foram avaliar a influencia de períodos de pastejo em trigo duplo propósito sobre a taxa de decomposição das plantas e liberação de nutrientes (N, P, K, Ca e Mg) bem como a produtividade de soja cultivada na sequencia em sistema de semeadura direta. Os tratamentos foram arranjados em delineamento blocos ao acaso com duas repetições. Os tratamentos foram os seis períodos de pastejo (0, 21, 42, 63, 84 e 105 dias) e a taxa de decomposição do material residual destes, foi avaliada pela técnica de litter-bag. A percentagem de biomassa e nutrientes no compartimento mais prontamente decomponível aumentou à medida que aumentou os períodos de pastejo, principalmente devido ao efeito do animal sobre a renovação dos tecidos foliares, o que resultou em uma maior taxa de decomposição da palhada e de liberação de nutrientes para o solo e, consequentemente para a cultura da soja cultivada na sequencia em sistema de integração lavoura pecuária. Entretanto a produtividade de grãos de soja reduziu com o aumento dos períodos de pastejo principalmente devido à diminuição de resíduo de matéria seca sobre o solo. / The aims of this work were to evaluate the influence of dual purpose wheat grazing periods on plant decomposition rates and nutrient release (N, P, K, Ca e Mg) and soybean yielded cultivate in sequence in no-till systems. Treatments were laid out as a random block design with two replications. The treatments were six grazing periods (0, 21, 42, 63, 84 e 105 days), on continuous stocking rate grazing method. From these treatments, dual purpose wheat biomass and nutrients decay constants were evaluated along 7 different field incubation periods (0, 15, 35, 63, 98, 139 e 196 days after soil deposition) by the litter bag technique. The percentage of biomass and nutrients at the easily decomposable compartment increases with the increase of grazing periods, due to the influence of the animal over the plants tissue turnover, which results in highest decomposition rate and nutrients release to the soil and consequently to the soybean cultivated in sequence on crop-livestock system. However the soybean grains yielded reduced with the increase grazing periods mainly due to the diminished of dry matter residue over the soil.
244

Sedimentary response to the tectonic uplift of the Kyrenia Range, northern Cyprus, in its Eastern Mediterranean tectonic setting

Palamakumbura, Romesh Niranjan January 2016 (has links)
The Kyrenia Range forms part of an approximately east-west lineament extending from northern Cyprus to southern Turkey. During Plio-Pleistocene the northern Cyprus segment of the lineament uplifted to ca. 1000 m above modern sea level. Plio- Pleistocene sediments document the uplift of the Kyrenia Range. A combination of sedimentology and a range of dating techniques including uranium series, optical stimulated luminescence (OSL), strontium isotopes and magnetostratigraphy are used to help understand the geological processes controlling uplift. Shallowing from a deepmarine basin to a shallow-marine, cool-water carbonate ramp represents the earliest uplift of the Kyrenia Range. The base of the carbonate ramp is made up of thick-bedded, benthic foraminiferal-rich grainstones, which are discontinuously overlain by calcareous red algal-rich rudstones. Erosively overlying this sequence is a coral- and molluscrich conglomerate, representing a short-lived relative sea-level fall. The upper part of the carbonate ramp sequence is composed of cross-bedded grainstone representing a shoreface environment. Interbedded with the upper grainstone facies are occasional fluvial conglomerates. The shallowing-upward marine environment represents the earliest emergence of the Kyrenia Range. After a major break in deposition, six marine and non-marine terraces (K0 to K5) reflect the sedimentary response to the main phase of tectonic uplift of the Kyrenia Range. The K0 terrace, the oldest and highest terrace, is composed of megabreccia and is interpreted as representing a major phase of rapid tectonic uplift. The K2-K5 terraces form a series marine to non-marine terraces on the northern flank of the range and also non-marine terraces on the southern flank of the range. The terraces on the northern flank each begin with a major marine transgression followed by a regressive sedimentary sequence. Marine environments range from nearshore open-marine below the storm-wave base, to shoreface, foreshore (beachrock), and backshore lagoonal environments. The non-marine environments range from aeolian dune to fluvial drainage systems. The fluvial systems are characterised by channelised debris-flow deposits interbedded with mudstones and palaeosols. The non-marine deposits on the southern flank of the range comprise a series of fluvial drainage systems. The fluvial systems on the southern flank of the range comprise a mixture of planar-bedded and channelised conglomerates, mudstones and aeolianites. Portable luminescence data are used to correlate quantitatively the K4 and K5 terraces on both the northern and southern flanks of the range. Each of the K4 and K5 terraces produce a unique luminescence signal, which is used as the basis for correlating the lower terraces. The unique luminescence signals of the K4 and K5 terraces are likely to be caused by varying sedimentary histories of the quartz and feldspar grains within the two terraces. The shallow-marine environments surrounding the Kyrenia Range prior to major uplift were dated using strontium isotopes and palaeomagnetism. The results of this dating suggest that marine environments persisted throughout the Early Pleistocene. U-series and OSL dating were used to date the K4 and K5 terraces on the northern flank of the range. The U-series results indicate that the marine deposits of the K4 terrace formed during several Middle Pleistocene interglacial stages. The OSL dating shows that the aeolian dunes of the K5 terrace formed during a Late Pleistocene glacial stage. The formation of the K2-K5 terraces was controlled by the interaction between tectonic uplift, climatic change and global eustatic sea-level change. The basal marine deposit of each terrace formed during an interglacial stage. Major fluvial deposition also occurs during the interglacial period as a result of a wetter climate. The inter-glacialglacial transition resulted in major fluvial erosion as a result of falling global sea-level. Aeolian carbonate deposition was dominant during the glacial stage, which represent arid climatic conditions. The only exception to this is the K4 terrace, which represents three glacial stages. The K1-K3 terraces can be correlated with the global sea-level curve suggesting approximate ages for each terrace, and ca. 600 ka for the entire K1- K5 terrace sequence. The Kyrenia Range underwent rapid uplift during the late Early Pleistocene at >1.2 mm/yr, followed by continuous but slower uplift during the Middle to Late Pleistocene. These results indicate that the uplift occurred in tandem with the Troodos Massif in southern Cyprus. The driving mechanism of the uplift of the Kyrenia Range is likely to be related to the collision of the Eratosthenes Seamount with the Cyprus trench to the south of the island. The seamount-trench collision resulted in compressional tectonics around Cyprus within the large-scale tectonic setting resulting from the early stages of convergence of the African and Eurasian plates.
245

An easy to use system for determining range cattle body condition

Tolleson, Douglas R., Schafer, David W. 10 1900 (has links)
4 pp. / determining body condition for effective cattle management
246

An Easy to Use System for Developing a Drought Management Contingency Plan

Tolleson, Douglas R. 10 1900 (has links)
5 p. / an easy to use framework to help develop a contingency plan for drought
247

Some interesting features of the coast range massif of British Columbia

Patmore, William Henry January 1936 (has links)
No abstract included. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
248

An appraisal of ungulate habitats in the ashnola resource management unit

Scheffler, Eike Gerhard January 1972 (has links)
The four major ecological variables, soils, climate, vegetation and fauna, were studied from May 1966 to November 1967 and again for a short period in 1969 on important California bighorn sheep {Ovis canadensis califomiana Douglas) ranges in the Ashnola region. Emphasis in this investigation was placed on completing the basic extensive resource inventory as well as on initiating experimental range rehabilitation practices for future management of critical forage resources on the winter ranges. The soils inventory was based primarily on the survey recently completed for the Canada Department of Agriculture (Green, in print) for the Princeton map sheet. Extrapolation for the eastern half of the study area was accomplished with the use of air photos and some additional ground surveys. The climatic factors measured were: air and soil temperature, precipitation, snow depth and evaporation. This was done by establishing two summer climatic transects and one snow depth transect. These transects were altitudinally spaced along available access roads. The vegetation analysis was conducted with the use of site specific species lists, point quadrat and line transects and air photos. Both the habitat and soil type maps were constructed from available air photo coverage and ground surveys. Ungulate distributions were mapped from ground observations, aerial helicopter surveys and previous reports. Range rejuvenation experiments, using large exclosures, fertilization and reseeding, were conducted concurrently with the inventory. Five sites were chosen for these rehabilitation trials. Soils in the study area vary from Brown and Dark Brown to Alpine Dystric Brunisols. The mid-grasslands occur predominantly on Chernozem!c, the Rego Dark Gray to Orthic Black soils. Related in large measure to the physiography of the region, large areas have nonproductive soils, talus slopes and sheer rocks; vegetative production is extremely limited on such sites. Altitude and exposure greatly affect the temperature and precipitation regime within the area. At low altitudes the moisture supply limits productivity. Summer evaporation is very high on exposed low grassland slopes. With rising elevation the precipitation generally increases, and evaporation and mean temperatures decrease. Exposure greatly affects the overall climatic regime. This is reflected in the variable vegetative cover and productivity. Climatic change, variable between years, caused considerable fluctuation in forage production between years. Vegetative zonation is clearly recognizable in the area. The zones and thus habitat types are altitudinally delimited. Fire, logging and ungulate grazing have caused much disturbance. Reseeding was not very successful, especially on stable plant communities on Juniper and South Slope. Fertilization had considerable effect on forage production on all sites. Standing crop increases, as measured by a single annual clipping during late July, were sustained for at least three years on the Poa sp. and Agropyron spicatum sites. Excluding ungulates from the five fenced sites resulted in changes in species composition, plant vigor and increased forage production. Some progressive trends towards climax were recognized on at least two sites in 1969. Climatic factors, primarily temperature and moisture supply, grazing history and soils, all contributed to local and annual variability in forage yields. Periodic protection of important grasslands from use and fertilization of some slopes show promise as management tools. / Land and Food Systems, Faculty of / Graduate
249

Phytophagous insects on the ashnola bighorn sheep range

Maynard, Richard John January 1972 (has links)
There are conflicting statements in the literature concerning the effects of phytophagous insects on rangeland grass yields. This preliminary study was intended to asses the use of range forage by insects, especially grasshoppers. The study areas were two south-facing slopes at about 5500 feet elevation in the Ashnola Resources Management Area in South Central British Columbia. A plant community analysis was made to determine which grasses and forbs were most numerous and which provided most ground-cover in selected areas. The communities under study were characterized by various combinations of four prominent grass species: Bluebunch Wheatgrass (Agropyron spicatum), Junegrass (Koeleria cristata), Kentucky Bluegrass (Poa pratensis), and Columbia Needlegrass (Stipa columbiana). Insect grazing damage to grasses was estimated by random sampling of individual grass blades. The "preferred" (most-utilized) species were Koeleria cristata, Poa pratensis, Poa secunda, and Stipa columbiana, in that order. Agropyron spicatum was not visibly utilized. Grasshopper numbers were estimated in several ways; the most common species were Camnula pellucida, C. xanthippus, and Melanoplus sanguinipes. Grasshoppers were least numerous on the climax Agropyron spicatum community where only 21% of the total grass was of the four preferred species, and where only 32% of the ground was covered by vegetation. Highest numbers of grasshoppers were found on a "disclimax" Poa community, where 90% of the grass was of a preferred species, and where the ground was 62% covered. Experiments to determine the effects of grasshoppers on grass yields used exclosure cages placed on three different communities (Stipa - Agropyron, Poa - Stipa, and Poa) in 1969 and 1970. In all areas the mean grass yields were higher inside the cages, but the differences were not statistically significant. This result is similar to those of other workers who have attempted to demonstrate effects of grasshoppers on rangeland grass yields; while grasshoppers consume a fairly large amount of grass, they appear to have little effect on the total standing yield of grass, as determined by an end-of-season clip of vegetation. Grasshoppers may be attracted to moist areas, for example plant communities dominated by succulent grasses, where they congregate on spots which have been clipped, trampled, grazed by livestock, or otherwise disturbed. In the absence of overgrazing by livestock, even high numbers of grasshoppers probably can do little permanent damage, since their grazing is distributed over a large number of healthy, intact plants. The mature grassland, dominated by Agropyron spicatum, seems to be relatively immune to dramatic developments in insect populations. / Land and Food Systems, Faculty of / Graduate
250

Measuring the shape of time-varying objects

Monks, Tim Peter January 1995 (has links)
This thesis describes the first implementation of a colour encoded structured light (CESL) range-finder capable of measuring the shape of time-varying or moving surfaces. The system is shown to have mean square accuracies of better than 0.5mm when measuring the shape of the human mouth during continuous speech sampled at 50Hz, and better than 0.2mm when measuring static objects of similar dimensions. In order to sample range at video-rates, the images of the scene to be digitised are stored on video tape. This allows the image processing to be performed off-line so the sampling rate of the system only depends on the frame-rate of the video equipment used. The work was motivated by the need to acquire information on mouth shape for acoustics of speech experiments so that the results presented are for measurements of mouth shape and objects relating to the field. The reasons for producing a new system, and the choice of CESL are discussed. The work covers the entire implementation of the range-finder, including code and slide design, feature extraction, feature interpretation, calibration and 3D reconstruction, and performance evaluation. A modification on the Blackman and Tukey classical power density spectrum (PDS) estimator was used for feature extraction which was shown to perform better than other techniques evaluated. The accuracy of detected features and the probability that they were not spurious was determined, based on the feature confidence output by the PDS estimator. Detected features were tracked to produce segments, and encoded as a directed acyclic graph (DAG) which was then matched with the original code sequence using a fast but sub-optimal technique. An existing camera calibration technique was used which was extended to include a second step for projector calibration. The projector model used was linear, had the correct number of degrees of freedom, and was particular to our stripe system.

Page generated in 0.0548 seconds