The post-glacial history of woodland in North Yorkshire has been studied using a wide variety of sources including existing environmental studies, archaeological data, documentary information, and place-names. A critical approach has been adopted involving comparative studies of the different sources. The environmental and archaeological data available for the prehistoric period are thought to indicate that until the end of the Atlantic climatic period the vegetation of North Yorkshire was primarily environmentally determined, though mesolithic woodland burning may have created-open spaces and encouraged the growth of hazel in the uplands. During the Neolithic and Bronze Age a gradual spread of dense-agrarian settlement and intensive clearance across areas with calcareous soils, and into some drift covered lowlands, is thought to have occurred. This was probably accompanied by pastoral exploitation of the more acidic uplands causing a structural change in some upland woodland reflected by the decline of Tilia. The Iron Age and early Roman period appear to have been a time of widespread clearance, affecting even areas such as the clay lowlands of the Vale of York. Woodland appears to have become restricted to slope and bog refugia at this time. Evidence for a post-Roman woodland recovery is patchy. Secondary woodland appears to have formed principally on steep slopes such as the moorland scarp and gill sides, and around lowland bogs. At the beginning of the medieval period there appears to have been a marked contrast between the largely woodless areas of the Vale of Mowbray and the Wolds, and the remaining areas which were relatively well wooded. With the exception of the eastern fringe of the Pennines, woodpasture appears to have been the dominant form of exploitation in most of the more wooded areas in the early Middle Ages. The expansion of coppice management appears to have been slow, accounting for only a small proportion of documentary references to woodland until the 14th century. After this coppicing appears to have become widespread while many common woodpastures were enclosed or lost their trees. By the mid-nineteenth century common woodpastures were rare, occurring mainly in the Pennine uplands, and plantation accounted for a significant proportion of woodland, particularly in areas with landscape parks. The evidence for distribution and management of woodland over a long time period has facilitated the construction of interpretive models for the influence of environment, economics, and social structure on woodland history. Whilst the interaction between the environment and economic considerations offers a good model for the broad trends in clearance, and woodland distribution, the chronology of the adoption of coppice management requires a more subtle explanation. The expansion of coppice is thought to have been delayed until after the Black Death as a result of a concerted defence of common by the tenantry, which may to a large extent have consisted of freeholders.

The end-Ordovician mass extinction dramatically altered the course of conodont evolution. This extinction event is probably unique in that it can be strongly correlated with a glacial climatic control. This study has identified, through the application of high-resolution stratigraphy, events within the extinction and recovery intervals. Elements of the uppermost Ordovician Shelf-edge Biofacies were severely affected by the oceanic cooling and introduction of cold-water currents associated with the initiation of the glacial maximum. In contrast, elements of the Shelf Biofacies were more severely affected by the intense cooling, shallowing and overcrowding during the glacial maximum. A number of the Shelf-edge taxa that had survived the glacial maximum suffered extinction at the hands of increasing water temperatures, rising anoxia and/or the cessation of oceanic circulation during the post-glacial transgression. Recovery was initiated by the appearance of Crisis Progenitor Taxa within the glacial maximum in the Shelf Biofacies and during the post-glacial transgression in the Shelf- edge- Slope biofacies. The Shelf-edge Biofacies identified within the uppermost Ordovician is not recognised in the Lower Silurian. Two main biofacies occurred on the Shelf and Slope, which had directly evolved from their Upper Ordovician equivalents. The long-term recovery involved the evolution of Crisis Progenitor Taxa and Ecological Generalists within the Shelf and Slope Biofacies (autochthonous taxa). Punctuated equilibrium likely predominated in the Shelf Biofacies as a consequence of widely fluctuating physical conditions. In contrast, the more stable environments of the slope encouraged gradualistic evolution within the Slope Biofacies (Plus ça change Model). Transgressive episodes within the Llandovery, possibly linked to eccentricity cycles, caused the iterative appearance of Long-term Refugia Taxa (allochthonous taxa), sourced from a Pterospathodontid Biofacies. The transgressive episodes also drove elements of the Slope Biofacies onto the shelf. It has been observed that the mechanisms driving extinction, namely environmental disruption and temperature changes, were also responsible for fuelling the subsequent recovery.

Thesis advisor: Noah P. Snyder / Land cover and climate changes, attributed to natural and anthropogenic forcings, cause deviations in geomorphic processes that act to deliver sediment from watersheds to lakes. In New England, contradictory evidence exists as to the influence of deforestation associated with EuroAmerican settlement and major flood events on watershed erosion rates over the past ~250 years. Through combining sediment core analysis from Ossipee Lake, New Hampshire with geomorphic analysis of the Ossipee Lake watershed, this study quantifies Holocene through Anthropocene watershed erosion rates, and assesses variations in rates in relation to short-term historic events such as major storm events or deforestation, and long-term variations related to natural climate variability and post-glacial landscape evolution. An 8.63 m core was collected and spans the entire period from deglaciation to present. Bulk composition and age-depth modeling, utilizing both short-lived radioisotopes and radiocarbon dating, are used to quantify changes in deposition and inferred erosion rates over time. Additional insight on sedimentary processes is provided by measurements of magnetic susceptibility and bulk geochemistry. Lake-sediment data suggests clastic sediment mass accumulation rates vary between 0.0032 to 0.5870 g/cm2/yr, with deposits of increased terrestrially derived sediment focused between ~8500 to 7800, ~6500 to 2500, and 1600 cal yr BP to present. Geomorphic analysis is used to identify regions within the watershed that act to deliver sediment to Ossipee Lake. Potential sources of sediment supply include loose, unconsolidated proglacial deposits near Ossipee Lake that transition to primarily till in upland areas. Calculated bed shear stress along rivers highlights areas in the watershed capable of transporting sediment and areas that can serve as traps thus limiting sediment delivery to Ossipee Lake. / Thesis (MS) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

During the late or post Weichselian glacial periods, about 9500 years ago, several faulting associated with large scale earthquakes were triggered in northern Fennoscandia. The end- or post-glacial scarps have a range of the lengths c. 3 to 155 km and the heights 0 to 30 m while most of them are reverse faults trending NE-SW with SE dips. In this literature study, I try to compile the estimated history and cause of seismicity in northern Sweden, and predict the future activity. The result indicates that although the timing of these faulting might not be in the same phase of deglaciation, the upheaval induced by glacial retreating is considered as the major factor of these paleoseismicity. Since the strain from glaciers has been mostly released, the main cause of recent earthquakes in this region is tectonic stress accumulation. Accompanied by the progress of observing techniques such as drilling and grand penetrating radar detection especially in this decade, the geometry of these glacially induced faults and recent micro-seismicity in the vicinity of these scarps have been detected better and better. According to the results, the recorded epicenters form clusters in the east side of the faults’ zone. It implies the correlation between recent seismicity and end- or post-glacial faults. However, there is still insufficient data of the faults’ structure and previous seismicity in order to clarify the faults’ geometry, the age of main movements and estimate their future activity. More investigations are expected to take place in this region.

No description available.

Parasitism in plants is often accompanied by a suite of morphological and physiological changes resulting in a condition known as the ‘parasitic reduction syndrome’. With changes including extreme vegetative reduction, frequently beyond any resemblance to its photosynthetic relatives, accompanied by significant losses of genes linked to photosynthesis, the study of parasitic plants can be challenging. Conopholis (Orobanchaceae) is a small holoparasitic genus distributed across eastern and southwestern North America and Central America. This genus has never been the subject of a molecular phylogenetic or morphometric analyses. In addition, very little is known of the relationships among populations and of their post-glacial history. To investigate the species limits and phylogenetic relationships in Conopholis, we conducted a comprehensive molecular phylogenetic study of the genus as well as a fine-scale morphometric study. Based on plastid and nuclear sequences, Conopholis was found to contain three distinct and well-supported lineages which have varying degrees of overlap with previously proposed taxa. The clustering and ordination analyses of the morphometric study corroborated the molecular data, demonstrating the morphological differentiation between the three lineages detected within Conopholis. A taxonomic re-alignment is proposed for the genus that recognizes three species, C. americana, C. panamensis, and C. alpina. To address genetic diversity and phylogeographic structure of C. americana in eastern North America, microsatellite markers were developed and characterized for the first time in this species. Using these newly generated markers along with sequences from the plastid genome, the persistence of a minimum of two glacial refugia at the last glacial maximum were inferred, one in Florida and southern Alabama and another in the Appalachian Mountains near the southern tip of Blue Ridge Mountains. The diversity seen across the southern Appalachian Mountains supports the hypothesis that populations derived from the southern and northern refugia come together in this area.

Parasitism in plants is often accompanied by a suite of morphological and physiological changes resulting in a condition known as the ‘parasitic reduction syndrome’. With changes including extreme vegetative reduction, frequently beyond any resemblance to its photosynthetic relatives, accompanied by significant losses of genes linked to photosynthesis, the study of parasitic plants can be challenging. Conopholis (Orobanchaceae) is a small holoparasitic genus distributed across eastern and southwestern North America and Central America. This genus has never been the subject of a molecular phylogenetic or morphometric analyses. In addition, very little is known of the relationships among populations and of their post-glacial history. To investigate the species limits and phylogenetic relationships in Conopholis, we conducted a comprehensive molecular phylogenetic study of the genus as well as a fine-scale morphometric study. Based on plastid and nuclear sequences, Conopholis was found to contain three distinct and well-supported lineages which have varying degrees of overlap with previously proposed taxa. The clustering and ordination analyses of the morphometric study corroborated the molecular data, demonstrating the morphological differentiation between the three lineages detected within Conopholis. A taxonomic re-alignment is proposed for the genus that recognizes three species, C. americana, C. panamensis, and C. alpina. To address genetic diversity and phylogeographic structure of C. americana in eastern North America, microsatellite markers were developed and characterized for the first time in this species. Using these newly generated markers along with sequences from the plastid genome, the persistence of a minimum of two glacial refugia at the last glacial maximum were inferred, one in Florida and southern Alabama and another in the Appalachian Mountains near the southern tip of Blue Ridge Mountains. The diversity seen across the southern Appalachian Mountains supports the hypothesis that populations derived from the southern and northern refugia come together in this area.

Here we examine seasonal grain-size trends on 18 beaches in the Northeastern US and dispersed along the post-glacial coast of Massachusetts (USA) in order to explore the mechanisms influencing median grain size and slope. Over 800 grain size samples were collected along 200 summer and winter cross-shore beach elevation surveys. Obtained grain size and beach slope data are compared to coastal morphology, sediment source, wave height, and tidal magnitude in order to ascertain controls on beach characteristics. In general, median grain size increases with intertidal beach slope in the study region. However, grain sizes along post-glaciated beaches in the study are as much as an order of magnitude coarser for the same beach slopes when compared to beaches for other regions of the US. Grain size and slope for beaches in the northeastern US also exhibit less correlation with oceanographic processes (i.e. wave climate and tidal magnitude). Instead, grain size trends are primarily driven by the composition of nearby glacial deposits that serve as the primary source of sediment to beaches in the study region. Results provide quantitative support for the distribution and composition of legacy glacial deposits rather than oceanographic conditions serving as the predominant governor of beach grain size along post-glaciated coastlines of the Atlantic continental margin.

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Abstract Knowledge of the determinants of the viability of populations is essential in order to undertake effective conservation and management of endangered species. In this study, long-term demographic data was combined with genetic data to study the viability of an endangered orchid species, Epipactis atrorubens. The genetic analyses revealed low levels of genetic variation and the presence of population genetic differentiation independent of the spatial scale. Low levels of seed-mediated gene flow, possibly linked to low seedling recruitment, is the likely cause of the low levels of gene flow. Indications of slow post-glacial colonisation rates were found, which together with the low gene flow predict a limited capacity of the species to shift its range to more suitable habitats after environmental change. Low genetic variation as a proxy for low evolutionary potential also suggests that the species has limited capacity to adapt to new environmental conditions. Furthermore, poor seedling recruitment lowers population viability in small populations, as highlighted by the low population growth rates. In addition, we found a strong effect of stochasticity that limits the viability of populations. Both the genetic and demographic analyses indicated low viability of the studied species and that seedling recruitment could be the main determinant for the viability. / Tiivistelmä Luonnonsuojelun perusta on populaatioiden elinkykyyn vaikuttavien tekijöiden tuntemus. Tässä väitöskirjatyössä tutkittiin uhanalaisen orkidean, tummaneidonvaipan (Epipactis atrorubens), elinkykyyn vaikuttavia tekijöitä yhdistämällä pitkäaikaisseurannoilla kerätyt demografiset aineistot geneettisin menetelmin kerättyihin aineistoihin. Lajin populaatioiden geneettisen muuntelun määrän havaittiin olevan pieni ja populaatioiden todettiin olevan geneettisesti erilaistuneita maantieteellisestä skaalasta riippumatta. Geneettisen erilaistumisen syy voi olla alhainen geenivirta, joka on seurausta vähäisestä siemendispersaalista ja huonosta taimettumisesta. Populaatioiden evolutiivista historiaa tutkittaessa havaittiin merkkejä hitaasta jääkauden jälkeisestä kolonisaatiosta, mikä yhdessä alhaisen geenivirran kanssa ennustaa, että lajilla on huono kyky siirtyä sille sopivammille alueille, jos ympäristö muuttuu. Huonoa evolutiivista potentiaalia kuvastava vähäinen geneettinen muuntelu ennustaa, että lajilla on huono kyky sopeutua uusiin ympäristöoloihin. Tämän lisäksi huono taimettuminen laskee elinkykyä etenkin pienissä populaatioissa, mikä näkyy muun muassa pienten populaatioiden matalina kasvukertoimina. Stokastinen vaihtelu vaikutti elinkykyä alentavasti, mikä pitäisikin huomioida nykyistä paremmin elinkykyanalyyseissä. Sekä geneettiset että demografiset analyysit osoittivat taimettumisen mahdollisesti olevan määräävä tekijä tummaneidonvaipan populaatioiden elinkyvylle.