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Στην παρούσα εργασία εξετάστηκαν τα πανιδικά σύνολα μικροαπολιθωμάτων με την χρήση 9 δειγμάτων που πάρθηκαν από ιζήματα Πλειστοκαινικής ηλικίας, και συλλέχθηκαν σε μία τομή που βρίσκεται ΒΔ των Αγίων Θεοδώρων και ανήκει στην ευρύτερη λεκάνη Σουσακίου. Κατά τη μελέτη προσδιορίστηκαν σε επίπεδο είδους όπου αυτό ήταν εφικτό, οστρακώδη, τρηματοφόρα, γαστερόποδα και δίθυρα. Τα δεδομένα αυτά χρησιμοποιήθηκαν ως δείκτες για την παλαιοοικολογική και παλαιοπεριβαλλοντική εξέλιξη μέρους της λεκάνης Σουσακίου. Προέκυψε ότι η ιζηματογένεση πραγματοποιήθηκε σε δύο λεκάνες ιζηματογένεσης, μια ρηχής θαλάσσιας προέλευσης και μια λιμνοθαλάσσιας . Οι δύο αυτές ακολουθίας ήρθαν σε επαφή μέσω της τεκτονικής. / In this project, the microfossil fauna of 9 samples were studied. The sedimentary sequence is of Pleistocene age and the samples were selected within a stratigraphic sequence located NW of Ag. Theodoroi village. These sediments are part of the sedimentary sequence of Sousaki basin. Ostracodes, Foraminifera , Gastropods and Bivalves were udentified. These data were used to reconstruct the palaeoecological and palaeoenvironmental evolution of part of the Sousaki basin. The sediments were deposited in two basins, one marine and one lagoonal. These two basins are in contact through tectonics.

The long term patterns of fire-climate interactions and forest recovery processes in subalpine forests are poorly understood. This study used a suite of dendrochronological techniques to identify tree growth-climate relationships, assess the interactions of fire with interannual climate variability, and reconstruct summer temperature in subalpine forests of the Selway-Bitterroot Wilderness Area on the border of Idaho and Montana, USA. Comparison of ring-width chronologies from whitebark pine (Pinus albicaulis Engelm.) and subalpine larch (Larix lyallii Parl.) with modern climate data indicated that summer temperatures were most limiting to growth in these conifers. Warm summers were generally conducive to radial growth. However, the temporal stability of the climate-tree growth relationship weakens from the early to later periods of the record. Alterations to growing season length, possibly modified by snow pack, may be related to the reduction in climate-growth relationships. A 748-year reconstruction of average summer temperature was developed that explains ≈36% of the variance of the instrumental record. Positive values of the coefficient of efficiency and reduction of error verification statistics indicated that the reconstruction was of good quality. Warm and cool periods in the reconstruction include a warm decade around the 1650s and prolonged cooling around 1700. Peaks in variance in reconstructed average summer temperature occurred at 87, 15, and 2 years. More than 2000 fire scar and age structure samples were used to evaluate fire-climate relationships. Comparison of widespread fire events to climate variables indicated dry conditions both during the fire year and one year before a fire. Multiple spatial patterns of drought and El Nino were related to widespread fire occurrence. Forest recovery following fires generally proceeds from lodgepole pine (Pinus contorta var. latifolia Dougl.) toward spruce-fir forests (Picea engelmannii Parry- Abies lasiocarpa (Hook) Nutt.). Two successional pathways occur, one beginning with an initial lodgepole pine stage, the other a spruce-fir stage. Initial composition was related to the presence of overstory lodgepole pine at the time of fire occurrence as well as the intervals between successive fires. Collectively, these results suggest a strong multi-year drought linkage between climate and fire, and dependence on fire intervals for structuring forest communities.

Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C3 Prosopis velentina (mesquite) trees, whereas the burned plots are open C4-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant-available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass 11 is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C3 shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C4 grasses to C3 shrubs in surface soil layers. δ¹³CSOM values indicate that the Holocene and Late Pleistocene were dominated by C4 grasslands, and the pre-Late Pleistocene vegetation was a C4-grass savanna with abundant C3 plants.

The primary objective of this research is to investigate relationships between extremes in central Sierra Nevada tree growth, temperature and precipitation and winter and summer atmospheric circulation. Using existing Sierra Nevada chronologies, I developed two mean chronologies for the period of overlap between instrumental and tree-ring records (1900-1987), one for giant sequoia (Sequoiadendron giganteum) and one for treeline pines (Pinus balfouriana, Pinus albicaulis) and selected the highest and lowest quintiles of tree growth as extreme years. For these years, I constructed and analyzed maps of composite anomalies for the following climatic data: tropospheric pressure (SLP, 700 mb, 500 mb), storm track (positive vorticity advection [PVA], a variable not previously used in dendroclimatology), temperature, precipitation, and snow (a variable often assumed have the same effects on growth as winter precipitation). Results suggest that extreme growth in these trees is associated with distinct patterns of winter atmospheric circulation and snow depth that are consistent with instrumental studies for the Western U.S. The storm track and snow analyses, seldom used in dendroclimatology, added substance to inferences based on analyses of tropospheric and surface climate parameters. This study shows the strong potential for reconstruction of these variables using Sierra Nevada trees. Synthesis of these results suggests that sequoia exhibit low growth during years with meridional winter and summer circulation, winter storms primarily occluded in the Gulf of Alaska, and low snow depth; sequoia exhibit high growth during years with low winter pressure in the north Pacific, long duration storms, a SW-NE oriented storm track entering North America at the California-Oregon border, high snow depth and zonal summer flow. Treeline pines exhibit low growth during years with enhanced ridging over the eastern Pacific, cool, short duration winter storms along a northern track, low snow depth and high east Pacific summer SLP; these pines exhibit high growth during years with warm, long duration winter storms following a southern track, a quasi-PNA atmospheric circulation pattern, average snow depth and a northeastward displaced summer subtropical high. Evidence presented herein suggests that variation in extreme treeline pine growth tracks low frequency changes in north Pacific atmospheric circulation.

The design and implementation of a computer-assisted tree-ring chronology composition system for dendrochronology is described in this thesis. Methods for tree-ring growth sequence pattern matching, hierarchical composition of master chronologies, and analytical quality control are discussed in detail and systematically implemented in the CROSSDATE program in a highly visual, graphic environment. The objective of this work is to provide dendrochronologists with a robust set of tools for comparing the relative growth patterns of tree-ring samples for purposes of dating the samples and composing new master chronologies from individual tree-ring samples and other master chronologies. This system is complementary to the TREES program, a computer-vision based tree-ring identification and measurement system developed at the University of Arizona.

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Rangeomorphs are a distinct group of millimeter- to meter-scale soft-bodied macrofossils that are restricted to the latter half of the late Neoproterozoic Ediacaran Period (635Ma- 542Ma). These fossils represent an extinct higher level taxon characterized by a modular construction based on a single architectural unit: the centimeter-scale, chevron-shaped rangeomorph element which displays several orders of self-similar branching. These elements could be arranged in a variety of different ways, constituting the wide array of gross morphologies found within the Group Rangeomorpha. The largest and most diverse assemblage of rangeomorph fossils in the world is found at Mistaken Point, on the Avalon Peninsula of Newfoundland, Canada, where these organisms are preserved within their original, in situ paleocommunities. Multibranched rangeomorphs are typified by bush-, comb- and network-shaped fossils which display multiple rangeomorph-bearing structures attached to an untethered basal stolon or central attachment point. Multibranched, comb-shaped rangeomorphs are endemic to Mistaken Point, and are represented by fossils displaying multiple parallel struts emerging along one side of an elongate, curved pedicle rod. Morphological and taphonomic evidence suggests that, in life, this organism had two rows of struts, each bearing a rangeomorph frondlet, arranged in an alternating pattern along the curved, tubular pedicle rod. Biometric analyses imply that the struts were added to both ends of the pedicle rod throughout the organism’s lifetime, with later inflation of the rangeomorph frondlets. Each comb-shaped rangeomorph locality likely represents a different age cohort within the organism’s lifecycle, providing rare evidence for spatfall reproduction in Ediacarans, which is similar to that found in modern macrobenthic organisms with pelagic larvae. Network-shaped multibranched rangeomorphs, represented by symmetrical to asymmetrical net-like fossils, are also endemic to Mistaken Point. This genus is reconstructed as having a symmetrical arrangement of flexible, rangeomorph-bearing leaflets that were, in part, neutrally buoyant with respect to the seawater. This flexible leaflet structure is unique, and shared only with a rare, previously undescribed, Ediacaran frond-like organism. It is suggested that the enigmatic leaflet structures shared by these two morphologically distinct taxa represent a new type of rangeomorph branching architecture, and therefore constitute a new type of rangeomorph. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2008-07-25 11:01:43.469

The ecotone between aspen parkland and mixed-grass prairie in mid-eastern Alberta is a climatically-sensitive area that has been subject to periods of enhanced aridity occurring at multi-decadal to centennial-scale cycles throughout much of the last 6000 years. To assess the ecotonal response to changes in effective moisture, as inferred by diatom-inferred salinity, temporal variations in pollen and charcoal preserved in a sediment core from Chauvin Lake were analyzed over several diatom-inferred moisture-cycles from c. 5,400 to 3,300 YBP. Changes in landscape vegetation were inferred by variation in both the percent relative abundance and influx rates of pollen taxa found in a sediment core from Chauvin Lake. Variation in sediment charcoal accumulation rates for both total charcoal and morphotypes, as well as the percent relative abundance of charcoal morphotypes, were used to infer changes in landscape fire regimes during these aridity cycles. One-way ANOVAs were used to determine significant differences in average accumulation rates or relative abundances between the arid and more mesic periods. Changes in the relative abundance of Cyperaceae and Ambrosia pollen between wet and dry periods suggests a shift in the spatial arrangement of vegetation, and a decrease in the sediment influx of most taxa, suggests a decrease in production of landscape vegetation during periods of aridity. Charcoal morphotype analysis, especially variation in Type M, Type D and Type B, suggests fewer, more intense fires during periods of drought. Lack of change in total charcoal may be related to increased secondary sedimentation of charcoal during periods of drought due to increased soil erosion. This study suggests that the spatial arrangement and production of landscape vegetation is dependent on climate, and fire prevalence decreases during periods of drought due to reduced fuel availability. / Thesis (Master, Biology) -- Queen's University, 2009-01-29 12:15:32.137