High-resolution records of early Holocene deposits are rare, and as a consequence reconstruction of terrestrial environments very soon after the deglaciation has often been difficult. In this study the palaeoenvironmental conditions of early Holocene (c. 10600-7500 cal. yr BP) are reconstructed in the Värriötunturit area of northeastern Finland, using evidence from plant macrofossils and pollen preserved in a lake sediment sequence retrieved from the small lake Kuutsjärvi. Special emphasis is put on the environment immediately following the deglaciation as the base of the sediment sequence is rich in minerogenic material interpreted to have been deposited by meltwater pulses from the retreating ice sheet. The abundance and variety of fossil remains in these early meltwater deposits provide evidence for a very productive ice-marginal environment in the area between the lake and the ice sheet, and the presence of tree-type Betula macro remains as well as high percentage values of tree-type Betula pollen suggests that a subarctic birch forest established just a few years after the deglaciation. In the following centuries the birch forest around the lake became rich in an under growth of ferns, and at c. 9400 cal. yr BP a transition into a mixed pine and birch forest took place. Due to absence of indicator plant taxa in the sediment it was not possible to reconstruct temperature conditions for any parts of the sequence in this study. However, the rapid colonisation of birch forests suggests that the climate was warm already during deglaciation, which is also in accordance with climatic conditions reconstructed for the early Holocene in the nearby Sokli area just 10 km away, as well as in other parts of Fennoscandia and Russia.

This thesis is a case study using paleoethnobotanical analysis of Kilgii Gwaay, a 10,700-year-old wet site in southern Haida Gwaii to explore the use of plants by ancestral Haida. The research investigated questions of early Holocene wood artifact technologies and other plant use before the large-scale arrival of western redcedar (Thuja plicata), a cultural keystone species for Haida in more recent times. The project relied on small-scale excavations and sampling from two main areas of the site: a hearth complex and an activity area at the edge of a paleopond. The archaeobotanical assemblage from these two areas yielded 23 plant taxa representing 14 families in the form of wood, charcoal, seeds, and additional plant macrofossils. A salmonberry and elderberry processing area suggests a seasonal summer occupation. Hemlock wedges and split spruce wood and roots show evidence for wood-splitting technology. The assemblage demonstrates potential for site interpretation based on archaeobotanical remains for the Northwest Coast of North America and highlights the importance of these otherwise relatively unknown plant resources from this early time period. / Graduate / cohenjenny2@gmail.com

Five lake and one soil sediment record from six mountainous sites on Vancouver Island, British Columbia, Canada, were examined for changes in pollen, macrofossils, charcoal, and mineral clasts to reconstruct late Quaternary history of vegetation, fire and climate. The results provide insights into the history and dynamics of the Mountain Hemlock biogeoclimatic zone and highlight the role of several species and species groups not previously recognized. During the early Holocene, Alnus crispa expanded throughout the region following deglaciation, playing a more important role in these ecosystems than today. Abies lasiocarpa was the dominant Abies species at these sites during the late glacial and early Holocene until it was replaced by A. amabilis between about 10,500 and 7300 calBP, perhaps due to changes in regional atmospheric circulation and greater seasonal variability in insolation than we experience today. A. amabilis increased during the mid Holocene and was later replaced at the sites by increased abundance of T. mertensiana while T. heterophylla became much more abundant at nearby low elevations. Ericaceous-heath communities were established soon after deglaciation at the moister sites but not until about 7000 calBP at drier sites. These drier sites show more variation in vegetation throughout their records than the wetter sites. High charcoal and clast concentrations coincident with rapid vegetation shifts during the early Holocene suggest that these changes were probably the result of large stand-clearing fires that exposed mineral soils. A peak in charcoal at several of the sites occurs at ca. 4000 calBP suggesting more frequent fire at that time. During the late glacial and very early Holocene, P. contorta was an important seral species until A. crispa became well established. In the mid to late Holocene when Ericaceous-heath became established, A. crispa was unable to predominate, possibly because of reduced fire activity or because the heath communities hindered the exposure of fresh mineral soil surfaces. As a consequence, conifer-dominated stands were favoured. Basal sediments from these sites are not as old as they are at lower elevations, suggesting that deglaciation may have happened later at higher elevations.