Plateau pika (Ochotonidae: Ochotona curzoniae) is widespread in Qinghai-Tibetan Plateau (QTP). It is endemic to QTP and restricted to high altitude area, ranging from 3,000 to 5,200 m above sea level. In this study, I examined the genetic structure of O. curzoniae along the Qinghai-Tibetan Railway (QTR) using mitochondrial cytochrome b sequences, and investigated whether QTR had become a barrier of gene flow to populations of O. curzoniae on its two sides. In total, I found 26 haplotypes of cyt b sequences from 29 individuals, of which the mean length was 1,190 bp including 68 informative sites, and the mean genetic distance was 1.7%. Two major clades were revealed in phylogenetic trees as well as TCS haplotype network. In general, the relative positions of haplotypes in the clades were corresponded to their geographic distribution. Most haplotypes of clade I were from east side, while all the haplotypes of clade II were from west side of QTR. Significant population differentiation was revealed between populations from the opposite sides of QTR, but not the same side. Due to the far smaller geographical distances between sampling sites between opposite sides than those of the same side, the differentiation pattern was not consistent with the theory of isolation by distance. Therefore, QTR might have resulted as a barrier to gene flow between populations of O. curzoniae living on opposite sides of QTR. The degree of genetic differentiation between populations of O. curzoniae on opposite sides of QTR will probably further increase in the future.

New applications of the optically stimulated luminescence (OSL) dating were carried out with the aim of understanding late Quaternary activities for the Tibetan Plateau. This included studying the slip rate of the Altyn Tagh Fault, northeast Tibetan Plateau, and revealing the environmental changes derived from large inland lake’s evolution, central south Tibet. Two deflected streams across the Altyn Tagh Fault close to Aksay (39°24.572’N, 94°16.012’E) were investigated. Geomorphological analysis suggests that loess covering deflected stream banks has recorded past faulting events. A conceptual model is proposed illustrating the relationship. OSL dating of sixteen loess samples at both streams support the model, suggesting the loess is deposited episodically after fault strikes and subsequent channel wall refreshment. The age and offset indicate a slip rate of 11 ±2 mm/yr for this part of the Altyn Tagh Fault. Another river section near Aksay was also investigated for the slip rate information. Two risers between three terraces are clearly offset; OSL dating of loess covering terrace surfaces yielded terrace ages. Using the upper-terrace age to represent riser displacement duration, the rate is estimated to be 12 ±1 mm/yr. The result suggests that using upper terrace is more suitable in this region. Notably, though, the slow rate is at odds with proposals that assume high-speed extrusion (~23 mm/year) of the Tibetan Plateau being accommodated by the Altyn Tagh Fault. Palaeo-shorelines around the third largest lake in Tibet, Zhari Namco, were for the first time systematically investigated using OSL dating. Twenty-two sediment samples from eleven shorelines indicate that the water level has dropped ~128 m and the lake has undergone stepwise shrinkage since 8.2 ka. Digital elevation model calculation indicates the lake has shrunk from 4605 km2 in size at 8.2 ka to 996 km2 at present, which is equivalent to ~300 km3 of water. This implies a significant reduction in precipitation over the past 8.2 ka, a result of weakening Indian Monsoon or a shift of monsoon circulation path. The result is consistent with other lake-core, ice-core climate proxies and solar insolation changes, implying the dominance of a weakening Indian Monsoon over central Tibet in the Holocene. Using the elevation of the highest shoreline of the four largest lakes in Tibet, the early Holocene Pan-lake hypothesis is proposed for the central Tibet. In addition to these applications of OSL dating, technical studies on sensitivity changes and residual doses have been carried out for potassium rich feldspar (K-feldspar). Recent development of infrared stimulated luminescence (IRSL) signals from K-feldspar has shown great potential for extending the datable range for OSL dating. Sensitivity changes and residual doses of post-IR IRSL and multi-elevated -temperature post-IR IRSL protocols for K-feldspar were studied. A sensitivity decrease is observed after adopting a high temperature IRSL. IRSL signals stimulated at high temperature are found to contain large residual doses. The residual dose rises with stimulation time, suggesting that the initial part of IRSL signals contains more easy-to-bleach signals comparing with the later part. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Groundwater and surface water in the Edwards Plateau region exhibits spatial variability arising from mineral differences in aquifers and mixing of groundwaters with diverse flow paths and ages. Integration of basic hydrochemical and isotope data (⁸⁷Sr/⁸⁶Sr, [delta]¹⁸O, [delta]D, ¹⁴C, ³H) document that groundwaters in the Lower Cretaceous Edwards-Trinity (Plateau) aquifer system reflect intermixing of modern and Pleistocene recharge. Pleistocene recharge occurred under cooler paleo-climatic conditions, based on [delta]¹⁸O variance of 4.59%, and flow traversed sub-cropping Permian evaporite and Triassic strata under hydraulic conditions that promoted upward flow into the Plateau system. Recharge areas may have been in topographically elevated areas in New Mexico that no longer are connected with the Plateau. Present distribution of groundwaters with higher SO₄/Cl values occurring beneath topographic divides on the Plateau suggests that modern recharge occurs preferentially in losing-stream networks and is inhibited on divides by low-permeability soils. Relationships between ¹⁴C, tritium, [delta]¹³C, and Mg/Ca values confirm that effectively younger groundwaters occur beneath the upper parts of drainage networks, but down slope of divides. Thus, groundwater-age and hydrochemical data suggest that recharge preferentially occurs in the upper parts of drainage networks. Correlations between groundwater relative age and Mg/Ca enable estimation of the proportion of modern recharge at specific well locations based on Mg/Ca values and enables estimating local absolute recharge rates from regional-scale recharge estimates obtained from regional flow models. The Upper Colorado River bounds the northern and northeastern margin of the Plateau system and shows systematic chemical evolution along its flow path, including decreasing salinity and increasing SO₄/Cl values. The stream can be conceptually divided into three segments that each reflect groundwater inputs from five hydrochemically distinct intervals: 1) deep Permian and Pennsylvanian reservoirs similar to those that produce hydrocarbons in the region; 2) Upper Permian halite (Salado Formation); 3) the Triassic siliciclastic aquifer (Dockum Group); 4) the sulfate-evaporite-bearing Permian system (Ochoan, Guadalupian, and Leonardian Series); and 5) the Plateau aquifer system. Conservative mixing models suggest that any aquifer that the river is traversing at a specific location contributes a distinct hydrochemical signature, but the dominant contribution is from the Plateau system. / text

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abstract: The highly-social plateau pika (Lagomorpha: Ochotona curzoniae) excavates vast burrow complexes in alpine meadows on the Tibetan Plateau. Colonies of over 300 individuals/ha have been reported. As an ecosystem engineer, their burrowing may positively impact ecosystem health by increasing plant species diversity, enhancing soil mixing, and boosting water infiltration. However, pikas are commonly regarded as pests, and are heavily poisoned throughout their range. The underlying assumption of eradication programs is that eliminating pikas will improve rangeland quality and decrease soil erosion. This dissertation explores the link between plateau pikas and the alpine meadow ecosystem in Qinghai Province, PRC. This research uses both comparative field studies and theoretical modeling to clarify the role of pika disturbance. Specifically, these studies quantify the impact of pikas on nutrient cycling (via nutrient concentrations of vegetation and soil), hydrology (via water infiltration), local landscape properties (via spatial pattern description), and vascular plant communities (via species richness and composition). The competitive relationship between livestock and pikas is examined with a mathematical model. Results of this research indicate that pika colonies have both local and community level effects on water infiltration and plant species richness. A major contribution of pika disturbance is increased spatial heterogeneity, which likely underlies differences in the plant community. These findings suggest that the positive impact of plateau pikas on rangeland resources has been undervalued. In concurrence with other studies, this work concludes that plateau pikas provide valuable ecosystem services on the Tibetan Plateau. / Dissertation/Thesis / Ph.D. Biology 2010

L'instabilité de Rayleigh-Plateau est utilisée dans les dispositifs d'impression à jet continu (CIJ) afin de piloter la dynamique de brisure des jets d'encre. Son étude dans ce cas de figure s'inscrit dans un cadre pluridisciplinaire relevant de la mécanique des fluides, de la rhéologie, ou encore de la physique des polymères. Le travail effectué se focalise sur l'influence des propriétés du fluide ainsi que de la géométrie de la buse d'impression sur cette dynamique. Ainsi, la caractérisation expérimentale des propriétés physicochimiques et rhéométriques des encres fait l'objet d'une attention particulière. La dynamique de brisure est ensuite modélisée à l'aide de différents logiciels de simulation numérique puis comparée aux expériences effectuées par ailleurs. Ces simulations prennent en compte lorsque c'est le cas les comportements non newtoniens des encres étudiées telles que leur propriétés rhéofluidifiantes ou viscoélastiques. Un lien étroit entre la dynamique de brisure et la forme du profil de vitesse en sortie de la buse est mis en évidence. Ce lien semble constituer une piste d'investigation particulièrement intéressante dans le cadre de la prédiction des dynamiques de jets obtenues par les dispositifs d'impression industriels. / Rayleigh-Plateau instability is used in continuous ink jet (CIJ) printers in order to drive ink jets breakup. Studies of such mechanisms are based on pluri-disciplinary concepts dealing with fluid mechanics, rheology and polymer sciences. The present work focuses on fluid properties and nozzles designs influences onto breakup dynamics. In this context, the experimental characterization of ink physical and rheological properties are of particular interest. Thereafter, jet dynamics computations are performed using several software and compared with experiences. Potential non Newtonian behaviours such as shear-thinning or viscoelasticity are modelled by computations. A close link between breakup dynamics and velocity profile at the nozzle exit is highlighted. This link is believed to bring crucial information for the prediction of jet dynamics observed in industrial printers.

Les calcaires du Dogger des plateaux de Vesoul et de Combeaufontaine, qui se situent sur les bordures nord du Fossé bressan, sont parmi les plus karstifiés de Haute Saône. Les plateaux de Vesoul et de Combeaufontaine, dépourvus le plus souvent d’écoulements superficiels, possèdent de très nombreuses formes karstiques (dolines, dépressions fermées de dimensions hectométriques, pertes, grottes, gouffres) inscrites dans les 5 formations calcaires du Dogger : Calcaires à entroques, Calcaires à polypiers, Grande Oolithe (Bajocien), Calcaires compacts (Bathonien) et Dalle nacrée (Callovien inférieur). Parmi ces formes, les dolines, de dimensions pluridécamétriques, sont les plus nombreuses et sont représentées surtout par des dolines dissymétriques localisées surtout dans les vallées sèches souvent perchées au-dessus des vallées principales. Sous les deux plateaux, les circulations des eaux souterraines s’effectuent dans de vastes réseaux de galeries en partie noyées, pouvant atteindre 9 km (Deujeau) et participent à une réorganisation de drainage vers le Fossé de la Saône. L’essentiel du karst est un karst infra-talweg développé en lien avec l’intense fracturation des calcaires du Dogger, qui correspond à l’amont, aux pertes inscrites dans les percées cataclinales des bordures nord des deux plateaux, aux phénomènes karstiques situés dans les vallées sèches et aux circulations souterraines sous les vallées, ainsi qu’aux sources souvent abondantes Font de Champdamoy), situées dans les vallées des bordures méridionales des plateaux et de la bordure occidentale du plateau de Vesoul. Les galeries souterraines sont orientées le long de directions N10° à N40°, conformes à la fracturation régionale ou perpendiculaires à cette direction pour les réseaux se développant par érosion régressive à partir de la bordure ouest du plateau de Vesoul. Le karst infra-talweg concerne au moins en partie aussi les cavités perchées, façonnées en relation avec l’incision des vallées, comme la grotte des Equevillons (+113 m) façonnée en régime noyé. Le karst de contact lithostratigraphique est particulièrement discret sur le plateau de Vesoul en raison de la faible épaisseur des marnes du Callovo-Oxfordien recouvrant la Dalle nacrée (< 50 m). L’ancienneté de la karstification, attestée par l’existence de galeries perchées jusqu’à près de 350 m d’altitude absolue, est confortée par la longueur des galeries souterraines (10% > à 2 km), les dimensions des salles, ou de celles des dépressions fermées hectométriques drainées vers l’endokarst. Les cavités les plus anciennes pourrait remonter au début du Quaternaire, lorsque le soulèvement régional lié aux mouvements jurassiens a entraîné une incision les long des vallées de la Saône et de l’Ognon d’environ 50 m. De cette période, daterait le décapage des altérites ferrugineuses sur les plateaux et leur piégeage dans plusieurs grottes, comme celle des Equevillons. L’intense karstification des calcaires du Dogger, liée à leur fracturation, rattachent davantage les formes des plateaux de Vesoul et de Combeaufontaine à celles d’un karst jurassien, plutôt qu’à celles des plateaux de mêmes altitudes de l’Est du Bassin parisien. / The Dogger Limestones of the plateaus of Vesoul and Combeaufontaine, which are located in the northern margin of the Bresse graben, are one of the most karstified areas of Haute-Saône Department. These plateaus don’t have active superficial flows. They have numerous karstic forms (sinkholes, forest hollows and closed depressions of hectometric dimensions, interrupted flows, caves, vertical shafts) in the 5 limestones formations of the Middle Jurassic (Dogger) : “Calcaires à entroques”, “Calcaires à polypiers”, “Grande Oolithe” (Bajocian), “Calcaires compacts” (Bathonian) et “Dalle nacrée” (Lower Callovian). The most numerous exokarstic forms are the multidecametric asymmetrical sinkholes, located on sections of dry valleys above the main valleys. Under the both plateaus, the subterranean waters flow in a vast networks of galleries, which could reach 9 km (Deujeau) and participate in a reorganization of drainage towards the graben of the Saône. The main part of the karst is an infra-talweg karst, which is developed in connection with the greatly fractured Dogger limestones. Its corresponds, upstreams, to the sinkholes of the consequent valleys located on the Dogger cuesta on the Northern borders of the both plateaus, under these plateaus, to the karstic active forms situated in dry valleys and to the subterranean circulations, and, on the Southern borders of these plateaus and the western border of the plateau of Vesoul to abundant emergences (Font of Champdamoy) situated in the main valleys. The subterranean galleries are oriented towards the N10° to N40° directions, in accordance with the regional faults or perpendicularly to these directions due to regressive erosion of the rivers from the Western border of the plateau of Vesoul. The infra-talweg karst also concerns high cavities, shaped in connection with valleys incision, as the cave of Equevillons (113 m) which has been shaped under conditions of drowned palaeovalleys. The forms of the lithostratigraphic karst is particularly not very numerous on the Vesoul plateau due to the low thickness of the Callovo-Oxfordian marls located on the « Dalle nacrée » formation (50 m deepth). The old age of the karstification is attested by the presence of karstic galleries until about 350 m ASL of absolute height, by the galleries lengths (10 % > 2 km), the sizes of the caves, or the presence of hectometric closed karstic depressions drained towards the endokarst. The most ancient cavities could be attributed to the beginning of the Quaternary Period, when a regional uplift occured in connection with the Jura tectonic movements and cause a general incision reaching 50 m deepth along the Saône and the lower Ognon valleys. The erosion of the ferruginous weathering profiles of the plateaus and the trapping of weathered sediments in caves (e.g. Equevillons) may be dated to this period. The intense karstification of the fractured Dogger limestones is closer to the forms of the Jura karst, rather than those of the Eastern Paris Basin, which is present at similar altitudes.

La posture, composante statique du contrôle moteur permettant une position érigée du corps, repose sur une décharge tonique des motoneurones innervant nos muscles antigravitaires. La décharge prend la forme de « potentiel de plateau » au niveau de motoneurones matures chez de nombreux vertébrés. Pour déterminer une éventuelle concordance entre l'émergence des propriétés de plateau et le développement postural, notre travail a eu pour but d'étudier la maturation et la nature ionique des potentiels de plateau des motoneurones innervant le muscle triceps surae (extenseur de la cheville) chez le rat nouveau-né.La réalisation de ces travaux de thèse nous a permis de dégager un mécanisme fondamental dans la genèse des propriétés de plateau des motoneurones lombaires. Ce mécanisme dont le fondement repose sur l'activation d'un « ménage à trois » jouerait un rôle majeur dans le développement moteur chez le rat. Dans la mesure où les potentiels de plateau des motoneurones sont fortement perturbés à la suite d'une lésion médullaire, cette avancée scientifique permettra éventuellement de mieux comprendre l'origine de certains déficits sensori-moteurs (spasticité, hyperalgésie...) et le développement de nouvelles stratégies thérapeutiques. / Posture allowing an erect posture of the body relies on spiking activity of motoneurons innervating antigravitary muscle. Discharge could take the form of plateau potential on mature motoneurons of numerous vertebrates. To determine a possible concordance between the emergence of plateau potential and postural control development, we studied the maturation and ionic nature of plateau potential of motoneurons innervating triceps surae muscle of neonatal rat.The conclusion of our work allows us to propose a fundamental mechanism in the genesis of plateau potential on lumbar motoneurons. This mechanism based on a "ménage a trois" seems to play an important role in the neonatal motor development. This scientific advance could eventually lead to a better understanding of the origin of some sensori-motor impairments (spasticity, hyperalgesia...) and development of therapeutic strategies.

Wetlands on the extensively afforested Tsitsikamma Plateau are prone to fire and according to foresters, they behave as fire channels that under bergwind conditions rapidly carry fire into plantations. The destruction of plantations causes great economic loss and MTO would therefore prefer to afforest some smaller wetlands to limit the fire hazard. This study was carried out in the middle of a drought period and sought to determine the influence of fire, plantation management and the environment on wetlands and its component species. This study of palustrine wetlands on the Tsitsikamma Plateau identified five wetland vegetation communities, in which plant species richness was relatively low. Plant compositional structure of wetlands is influenced by wetland location, the height of the adjacent plantation and fire frequency. This study found a pronounced plant species turnover from west to east and soil coarseness increased along the same gradient. Re-sprouters dominated the wetland communities in the Tsitsikamma but a few populations of the obligate re-seeding ‘Near threatened’ Leucadendron conicum rely on fire for rejuvenation purposes. Regarding dragonflies in wetlands, abundance was found to be low, while species richness was relatively high considering the absence of surface water. The study found that fire indirectly influenced dragonfly abundance and species composition by altering vegetation structure. Dragonfly abundance and species richness was generally higher in wetlands with older vegetation (≥ 9 years). Further, most dragonflies frequenting the palustrine wetland habitats were females. Seeing that female dragonflies spend most of their time away from prime breeding habitats to escape male harassment, the study indicated these wetlands as important refuge habitats for them. Dragonfly abundance is expected to increase once the drought ends; however, the overall patterns observed are likely to remain unchanged under wetter conditions. Narrow wetlands (< 10 m) are few on the plateau and it is not advisable to sacrifice wider wetlands in the Tsitsikamma. Further, with regards to ecological processes and wetlands’ influence on the surrounding Tsitsikamma matrix, more research is needed before wetlands may be sacrificed. To deal with the fire risk the Tsitsikamma environment poses to plantations, it is strongly recommended to establish and maintain a cleared buffer area between plantations and wetlands. Further, for vegetation rejuvenation purposes, it is important to burn wetlands at irregular intervals but not more frequently than every nine years and not less frequently than every 25-30 years.

The lithostratigraphy and Pliensbachian ammonite fauna of a sequence of Pliensbachian to Bajocian sedimentary rocks, informally referred to here as the Spatsizi Group, from the Spatsizi map-area (104 H) in north-central British Columbia are examined in this thesis. Twenty Five species of ammonites representing fifteen genera from Pliensbachian rocks of the Spatsizi Group are described and their stratigraphic ranges in the thesis area determined. The Spatsizi fauna is comprised primarily of ammonites of Tethyan aspect and also contains elements endemic to the East Pacific faunal realm. The Spatsizi fauna is located on the northern half of the Stikine terrane of the western Cordilleran eugeocline, and is surrounded by biogeographically related faunas containing ammonites of Boreal affinity in addition to Tethyan and East Pacific forms, indicating that northern Stikinia occupied a position within the mixed Boreal/Tethyan zone of the eastern Pacific region during the Pliensbachian. Subsequent tectonic displacement of Stikinia transported it northward to its present position. The Spatsizi Group is informally defined and is divided into five informal formations; the Joan, Eaglenest Gladys, Groves, and Walker Formations. Each formation reflects deposition in a different sedimentary environment affected by varying degrees of volcanic (epiclastic or pyroclastic) input Rocks of the Spatsizi Group represent the basinward sedimentary equivalents to the coeval Toodoggone volcanics that formed along the southern flank of the Stikine Arch. Facies transitions from the Stikine Arch in the north to the sedimentary basin in the south are best developed in sediments deposited during Pliensbachian and Early Toarcian times, when epiclastic sands and conglomerates accumulating on the southern flank of the arch graded southward into silts and muds in the basin. Two phases of non-coaxial deformation folded and faulted the rocks in the thesis map area. Deformation was probably related to interaction between the Stikinia and the North American continental margin during accretion. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate