Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 141-151).

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Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: There is increasing evidence that the rapid and anomalous changes in climate experienced in the last century have had widespread ecological impacts. Indeed, sub- Antarctic Marion Island has experienced particularly large increases in temperature and declines in rainfall. However, the effects of these changes on the island's extensive fellfield vegetation remain largely unexamined. The aim of this study was to examine the sensitivity of a dominant and keystone fellfield plant species, the cushion-forming Azorella selago Hook. (Apiaceae), to changes in climate. Three complementary approaches (two mensurate, one experimental) were used, and all showed that A. selago is likely to change in response to further changes in climate. First, the unimodal age class distribution of A. selago suggested that the species' establishment is episodic, and therefore reliant on specific (possibly climatic) conditions. Azorella selago growth rate was related to environmental factors, suggesting that both the establishment and growth rate of the species is likely to be sensitive to changes in climate. Second, altitudinal variation in A. selago plant attributes suggested that the species' morphology would be responsive to changes in climate (assuming that a spatial gradient in climate is a suitable analogue for similar changes in climate over time). Plant height, leaf size and trichome density differed most consistently over altitude across the island. The altitudinal range of some epiphyte species, as well as the cover and species richness of epiphytes growing on A. selago, also showed consistent patterns along the altitudinal gradient. These cushion plant and epiphyte attributes appeared to be related to climatic factors, and are therefore predicted to change in response to further shifts in climate. Finally, A. selago showed a rapid vegetative response to short-term experimental reductions in rainfall and increases in temperature and shading. Reduced rainfall accelerated autumnal senescence, shortening the species' growing season. Plants were relatively unaffected by the magnitude of warming imposed, although the foliar nutrient concentrations of some elements were higher in warmed plants than in control plants. Experimental shading of A. selago (simulating a predicted indirect effect of climate change: increased cover of the dominant epiphyte species, Agrostis magellanica (Lam.) Vahl (Poaceae)) caused greater stem elongation, and the production of larger, thinner leaves, with lower trichome densities and higher foliar nutrient concentrations of some elements. Given this sensitivity of A. selago to shading, it is possible that changes in epiphyte load could overshadow the direct effects of changes in climate on this species. Ongoing changes in climate are predicted for the next century. Based on the results of this study the following scenarios are proposed. Continued warming and drying of the island will potentially favour the upslope expansion of A. selago (although also shortening its growing season) and decrease the abundance of its dominant epiphyte. Under such a scenario fellfield primary production may decline. In contrast, under warming alone, most epiphyte species could increase in abundance and expand their altitudinal ranges upslope. This would bring about much heavier shading of A. selago plants, leading to a short-term increase in stem growth and leaf nutrient concentrations. However, ultimately a decline in A. selago abundance and production would also be expected if cushion plants experience stem mortality under longer-term shading. Nonetheless, monitoring A. selago leaf size, trichome density and phenology, as well as the altitudinal range of dominant epiphyte species (attributes that this research suggests may be most sensitive to short-term changes in climate), will indicate the biological consequences of these changes in climate. This study, therefore, shows that further climate changes on Marion Island will affect A. selago and its epiphytes, with likely repercussions for fellfield communities. / AFRIKAANSE OPSOMMING: Daar is toemende bewys dat die vinnige en onreëlmatige veranderinge in klimaat oor die laaste half-eeu wye ekologiese gevolge gehad het. Inderdaad, sub-Antarktiese Marion Eiland het 'n ook 'n besondere groot toename in temperature en daling in reënval ervaar. Nogtans is die gevolge van hierdie veranderinge op die eiland se uitgebreide dorveld (fellfield) plantegroei nog nie nagevors nie. Die doel van hierdie studie was om die sensitiwiteit van 'n dominante hoeksteen spesie, die kussingvormige Azorella selago Hook. (Apiaceae), aan veranderinge in klimaat te ondersoek. Drie aanvullende metodes (twee waarnemend, een eksperimenteel) was gebruik, en al drie het aangedui dat A. selago waarskynlik sal reageer op verdere veranderinge in klimaat. Eerstens, die enkelpiek-vormige ouderdomsverspreiding van A. selago dui daarop dat die spesie ongereeld vestig, en is daarom afhanklik van spesifieke (dalk klimatiese) toestande. Verder, was A. selago se groeitempo aan omgewingsfaktore verwant. As gevolg hiervan sal die spesie se vestiging en groeitempo vermoedelik sensitief vir klimaatsveranderinge wees. Tweedens, veranderinge in A. selago eienskappe met 'n toename in hoogte bo seespieël (hoogte) dui daarop dat die spesie se morfologie sal reageer op veranderinge in klimaatstoestande (op voorwaarde dat 'n ruimtelike verandering in klimaat goed ooreenstem met 'n soortgelyke verandering in klimaat oor tyd). Planthoogte, blaaroppervlakte en trigoomdigteid het geleidelik met hoogte verander oor die eiland. Die verspreiding en bedekking van sommige epifitiese spesies, asook epifiet spesie rykheid, was ook aan hoogteverwant. Hierdie verwantskap tussen A. selago (en die epifiete) en hoogte is vermoedelik deur klimatiese faktore veroorsaak, en daarom word voorspel dat dit sal verander soos die klimaat verander. Laastens, het A. selago 'n vinnige vegetatiewe reaksie tot korttermyn eksperimentele vermindering in reënval en toename in temperatuur en beskaduwing gewys. 'n Afname in reënval het blaarveroudering versnel, en dus A. selago se groeiseisoen verkort. Plante het min verander as gevolg van hoër temperature, alhoewel die konsentrasie van sommige plantvoedingstowwe hoër was in blare van verwarmde plante as in die wat gewone temperature ervaar het. Eksperimentele beskaduwing van A. selago (wat 'n verwagde indirek effek van klimaatsverandering naboots, naamlik die toename in bedekking van A. selago deur die dominante epifiet spesie, Agrostis magellanica (Lam.) Vahl (Poaceae)) het stingel groei versnel, en veroorsaak dat groter en dunner blare met laer trigoomdigthede en hoër konsentrasies van sommige plantvoedingstowwe op die plante groei. As gevolg van die sensitiwiteit van A. selago op beskaduwing, is dit moontlik dat die gevolge van veranderinge in die bedekking van epifiete belangriker sal wees as die direkte gevolge van klimaatsverandering. Verdere klimaatsveranderinge word vir die volgende eeu voorspel. Gebasseer op die resultate van hierdie navorsing, word twee moontlike toekomstige omstadighede voorgestel. Toenemende verwarming en verdroging van die eiland sal vermoedelik veroorsaak dat A. selago op hoër hoogtes voorkom (alhoewel die spesie se groeiseisoen ook sal verkort), en dat die volopheid van A. magellanica sal afneem. In so 'n geval sal dorveld se plantproduksie waarskynlik effens verminder. In teenstelling, as die eiland slegs verwarm (sonder 'n verandering in reënval) kan die volopheid en verspreiding van epifiet spesies waarskynlik toeneem. Dit sal vermoedelik tot 'n toename in the verskaduwing van A. selago lei, wat tot 'n kort-termyn verhoging van stingel groeitempo en plantvoedingstof konsentrasies sal lei. Alhoewel, uiteindelik, word 'n vermindering van A. selago volopheid en groei verwag as plantstingels van lang-termyn beskaduwing vrek. Nietemin, as die blaargroote, trigoomdigteid en groeiseisoenlengte van A. selago en die hoogte verspreiding van die dominante epifiet spesie gemonitor word (eienskappe wat deur hierdie studie aangedui is as gevoelig aan kort-termyn veranderinge in klimaat), kan die biologiese gevolge van hierdie klimaatsveranderinge aangewys word. Hierdie navorsing bewys dus dat verdere veranderinge in klimaat op Marion Eiland 'n invloed sal hê op A. selago en geassosieerde epifiete, met moontlike gevolge vir die hele dorveld gemeenskap.

The Friis Hills is an isolated plateau standing as much as 600 m above surrounding topography in the McMurdo Dry Valleys region or Antarctica.Preserved on the plateau surface is a sequence of early to middle Miocene-aged dritis. At the eastern edge of the plateau, these drifts fill a shallow paleovalley to a depth of at least 35 m. The drills are exposed in a natural cross-section where modern topography crosscuts the paleovalley. Establishing an age and an environmental interpretation for these deposits is important because Antarctic paleoclimate records are lacking from the Mid-Miocene Climate Optimum. Two drifts fill the ancient paleovalley in the eastern Friis Hills. The upper drift is here named Cavendish drift: the lower is here named Friis drift. Cavendish can be subdivided into three units, whereas Friis drift can be subdivided into two units. Each of these units is a horizontal bed that laps on paleovalley sidewalls. The lowest, Friis II, is a compact diamicton that is overlain by a nearly in-situ bedded volvanic ash. Based on [20]Ar/[39]Ar dating, the ash is 19.76 [plus/minus] 0.07 Ma old. A second diamicton, Friis I, conformably blankets Friis II and was discovered to hold fossileferous interbeds. Both Friis I and II contain erratic clasts and both are lodgemont tills deposited from small, locally derived, alpine glaciers. Bedrock striations show ice flow to the northeast at azimuths between 025? to 032?, parallel to the trend of the paleovalley axis. Above these, Cavendish I. II. and III were deposited when thick ice covered the Friis Hills. Where the Cavendish drift laps onto paleovalley sidewalls, bedrock striations show ice flow from 077? to 150?. Cavendish drift was deposited sometime alter 19.8 Ma but before 14 Ma. when the Dry Valleys glacial records show that regional glaciers became cold-based. Downcutting eventually isolated the Friis Hills plateau, resulting in the preservation of the drift sequence. This event was most likely associated with growth or the East Antarctic Ice Sheet 14 Ma ago. This age constraint means that the tills preserved in the Friis Hills date from a time just before the East Antarctic Ice Sheet expanded and became a permanent feature. Based on the age-dated stratigraphy presented in this thesis, future work focusing on fossiliferious interbeds could provide unique and important constraints on Miocene climate change. / North Dakota State University. Department of Geosciences

Chapter 1: Antarctic fishes are extremely cold adapted. Despite their inability to upregulate heat shock proteins, recent studies have demonstrated a capacity for heat response in these animals. A cDNA microarray study looked at the Notothenioid fish Trematomus bernacchii and revealed heat sensitivities for hundreds of genes, two of which code for members of the CCAAT/Enhancer-binding protein (C/EBP) family of transcription factors. These molecular switches are best known for their roles in apoptosis, inflammation and cell cycle arrest. This dissertation further elucidates the role of C/EBP-delta in the Antarctic fishes T. bernacchii and Pagothenia borchgrevinki. Chapter 2: C/EBP-delta is constitutively expressed in unstressed, field-acclimated (ca. -1.86°C) animals in a highly tissue-specific manner. White muscle tissue contains the highest C/EBP-delta concentration, which is further increased in response to sublethal heat stress at 2.0 or 4.0°C. This response is mostly acute and transitory, but a lesser upregulation was observed in fishes held for one month at 4.0°C. Chapter 3: The heat-induced nuclear translocation of C/EBP-delta--as determined by immunohistochemistry--appears to be time, tissue and species specific with spleen, heart and retinae being particularly responsive in certain situations. Chapter 4: Protein concentrations of proliferating cell nuclear antigen are tissue specific and variably heat responsive. Surprisingly, levels appear to be positively correlated with C/EBP-delta. Chapter 5: Flow cytometry revealed increasingly high temperatures reduce the proportion of G1 cells while increasing the abundance of apoptotic cells. Chapter 6: These findings are discussed in the context of global climate change and the cellular stress response.

Permafrost is a variable in Antarctic terrestrial ecosystems, and the role it plays in the cryosphere is not well understood. There is much still to be learnt about the thermal state, physical properties, thickness and age of permafrost in Western Dronning Maud Land (WDML). Active layer dynamics and observed change over time have the potential to improve our knowledge of climate change. Understanding the effects of a warming climate on permafrost can also be of benefit to infrastructure, especially in areas with a large amount of frozen ground such as Scandinavia, Canada and Russia. Active layer and permafrost dynamics of WDML, Antarctica, are presented and discussed using data from six study sites, namely the Robertskollen, Vesleskarvet, Flarjuven, Grunehogna, Slettjfell nunataks and the Troll research station in the Jutulsessen area. Ground and ambient air temperature, as well as ground moisture data were collected for each site. An inventory of active layer and permafrost landforms was compiled, as were the frequency of cycles over the zero-degree isotherm, and the depth of the active layer. Furthermore, 3D models, geo-referenced maps and Digital Elevation Models were created of study areas with the use of an Unmanned Aerial Vehicle (UAV). Polygonal features are the most common landscape feature and are common to most of the study sites. Robertskollen has the deepest active layer at over 66cm and Slettfjell the shallowest at 9cm. A maximum recorded air temperature of 8.76°C (10/11/2014) occurred at Troll with the second highest maximum of 6.77°C (22/12/2010) recorded at Vesleskarvet. Robertskollen has the highest observable biological growth and a maximum recorded ground temperature of 22.84°C (10/01/2014). Troll and Valterkulten, registered the second and third highest ground temperatures respectively. The high ground Temperature observed for Robertskollen may be ascribed to it being the lowest altitude site. The highest number of cycles over the zero-degree isotherm was observed at Troll (11.01%), followed by Robertskollen (10.99%). For relatively warm areas, such as Robertskollen it is recommended that two metre borehole loggers are installed in order to capture a detailed understanding of the active layer. The UAV proved to be a beneficial tool for capturing aerial photographs for post fieldwork analysis and 3D modelling.

Investigating openwork block accumulation has the potential to further our understanding of rock weathering, the control of geological structure on landforms, the production of substrates for biological colonisation and the impacts of climate change on landform development and dynamics. Various models for the development of these landforms have been proposed. This includes in situ weathering, frost heave and wedging. Furthermore, it has been suggested that cold-based ice has the potential to preserve these features rather than to obliterate them. Blocky deposits are also frequently used as proxy evidence for interpreting palaeoclimates. The morphology and processes acting on a blockfield located on the Northern Buttress of the Vesleskarvet Nunataks, Dronning Maud Land, Antarctica (2°W, 71°S) were investigated and characterised. Given block dimensions and orientations that closely resembled the parent material and only small differences in aspect related characteristics observed, the blockfield was found to be autochthonous with in situ block production and of a young (Holocene) age. Small differences in rock hardness measurements suggest some form of aspect control on rock weathering. South-facing sides of clasts were found to be the least weathered. In comparison, consistently low rock hardness rebound values for the north-facing aspects suggest that these are the most weathered sides. Additional indicators of weathering, such as flaking and pitting, support analyses conducted for rock hardness rebound values. Solar radiation received, slope gradients and snow cover were found to influence weathering of clasts across the study site. Furthermore, ambient temperatures and wind speed significantly influenced near-surface ground temperatures dynamics. However, the lack of a matrix and paucity of fine material in textural analyses suggest a limited weathering environment. It is suggested that the retreat of the Antarctic ice sheet during the last LGM led to unloading of the surface, causing dilatation and subsequent fracturing of the bedrock along pre-existing joints, leading to in situ clast supply. Subsequent weathering and erosion along other points or lines of weakness then yielded fines and slight edge rounding of clasts.