Sökning: "permafrost history"
Visar resultat 1 - 5 av 6 avhandlingar innehållade orden permafrost history.
1. Holocene dynamics in subarctic peat plateaus of west-central Canada : Vegetation succession, peat accumulation and permafrost history
Sammanfattning : Dynamics in vegetation, permafrost and peat and net carbon accumulation rates throughout the Holocene have been studied in two subarctic peat plateaus of west-central Canada through plant macrofossil analysis, geochemical analyses and AMS radiocarbon dating. Peatland formation at the studied sites began around 6600-5900 cal yr BP as a result of paludification of upland forests. LÄS MER
2. Subarctic ecosystem responses to climate, catchment and permafrost dynamics in the Holocene
Sammanfattning : This thesis assesses aspects of the wetland development, permafrost dynamics and associated changes in carbon and nutrient cycling of the Stordalen Mire in northern Sweden. Various ecological and biogeochemical analyses of one peat and two lake sediment sequences were conducted, including analyses of organic matter and carbonate content, mosses, diatoms, testate amoebae, pigments, carbon and nitrogen and their stable isotopes, near infrared spectroscopy and biogenic silica. LÄS MER
3. Temporal and spatial dynamics in subarctic peat plateaus and thermokarst lakes
Sammanfattning : Permafrost peatlands are widespread at high northern latitudes and are important soil organic carbon reservoirs. A future warming in these areas, as suggested by global climate models, can cause thawing and increased ground subsidence (thermokarst), resulting in changes in surface hydrology and ecosystem functioning. LÄS MER
4. The Torneträsk System - A basis for predicting future subarctic ecosystems
Sammanfattning : Arctic and subarctic areas have experienced a rapid warming and substantial increases in precipitation in recent decades. The frequency and intensity of some extreme events, such as fires, winter warming events, extreme rainfall, and droughts, has also increased. LÄS MER
5. Palaeogenomic reconstruction of woolly mammoth evolutionary history and extinction dynamics
Sammanfattning : Biodiversity is declining globally. Yet, the biological and genetic processes associated with these declines on a longer timescale are still poorly understood. Ancient DNA is a powerful tool to study evolution in real-time. Despite advances in the field, there is further need for refinement of laboratory and computational techniques. LÄS MER