Peatlands, volcanoes and climate : ecological and palaeoecological studies in Alaska and Scotland
This thesis investigates direct and indirect volcanic impacts on peatlands using palaeoecological and ecological techniques. The primary approach used is palaeoecological studies across tephra layers. A multi-proxy methodology was adopted including testate amoebae, hurnification and outline macrofossil analysis supported by radiocarbon dating. To allow quantitative interpretation of testate amoebae results a transfer function model was developed for surface wetness and pH. To examine whether it is justified to use tephra layers as evidence of volcanic activity an experiment was carried out to investigate tephra taphonomy. Results show that tephra does move through peat but the majority remains at the surface. In an attempt to characterise the palaeoecological response to volcanic acid deposition an experiment was conducted applying tephra and acids to a Scottish peatland. Results show drastic impacts on peatland plants but impacts on other variables were more equivocal. For the palaeoecological studies a series of peatland sites were sampled in southeast Alaska and on the Kenai Peninsula in south-centra Alaska. A number of microscopic and visible tephras were located and subjected to electron microprobe analysis to aid their identification. Results show the great potential of microtephrochronology to extend the distribution of tephra layers in Alaska. Furthermore, results highlight the great size of several eruptions, improve the dating of others and show the presence of previously unrecognised tephras. The macrofossil and testate amoebae results show impacts associated with some tephras but not all. The hurnification results are considered unreliable due to a methodological problem. The most likely cause of the impacts is through volcanic acids and gases or other chemicals adhering to tephra shards. The variability of impacts may be due to the season of eruption. These results have implications for the volcano-climate system, peatland conservation and agriculture.