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Visar resultat 1 - 5 av 75 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Land-atmosphere interaction of a subarctic palsa mire

   Författare :Marcin Jackowicz-Korczynski; Institutionen för naturgeografi och ekosystemvetenskap; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; eddy covariance; chamber; methnaol; isoprene; nonmethane hydrocarbons; methane; carbon dioxide; carbon; mire; permafrost; subarctic; palsa; greenhouse gas;

   Sammanfattning : The main objective of this thesis was to quantitatively estimate the gaseous exchange of carbon dioxide (CO2) and methane (CH4) between a subarctic wetland ecosystem and the atmosphere. Additionally some initial estimates of the carbon input to the atmosphere of nonmethane hydrocarbons (NMHCs) were also obtained by combining different techniques in a joint setting. LÄS MER

3. 2. Biogeochemistry in Subarctic birch forests : Perspectives on insect herbivory

   Författare :Jeppe Ågård Kristensen; MERGE: ModElling the Regional and Global Earth system; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Biogeochemistry; Aboveground-belowground interactions; Herbivory; Insects; Subarctic; Birch; soil microbes;

   Sammanfattning : Herbivory can influence ecosystem processes, partly through long-term changes of the plant community compositions, but also more rapidly through the herbivores’ digestive alteration of the organic matter that is cycled through the soil and back to the primary producers. In the Subarctic mountain birch (Betula pubescens ssp. LÄS MER

4. 3. Holocene dynamics in subarctic peat plateaus of west-central Canada : Vegetation succession, peat accumulation and permafrost history

   Författare :A. Britta K. Sannel; Peter Kuhry; Peter Jansson; Ian Brown; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; peatlands; permafrost; carbon accumulation; fire; subarctic; Holocene; Physical geography; Naturgeografi;

   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

5. 4. Winter browsing by moose and hares in subarctic birch forest : Scale dependency and responses to food addition

   Författare :Sara Öhmark; Thomas Palo; Glenn R. Iason; Bengt-Gunnar Jonsson; Lisa Shipley; Mittuniversitetet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Herbivory; subarctic; hare; moose; spatial scale;

   Sammanfattning : Despite their difference in body size and morphology, the moose (Alces alces) andthe mountain hare (Lepus timidus) sustain themselves during winter on similar plantspecies and plant parts in in subarctic environments, namely apical twigs ofmountain birch (Betula pubescens ssp. czerepanovii). LÄS MER

7. 5. Temporal and spatial variability of carbon cycling in a subarctic landscape

   Författare :Torbjörn Johansson; Institutionen för naturgeografi och ekosystemvetenskap; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Geologi; physical geography; Geology; Växtekologi; Plant ecology; Permafrost; Herbivory; Subarctic; Aerial photography; Vegetation change; Carbon balance; fysisk geografi;

   Sammanfattning : This thesis deals with the carbon balance in a subarctic landscape at different temporal and spatial scales. Its focus is mainly on the peatland and mountain birch forest (Betula pubescens ssp. czerepanovii) ecosystems within the Abisko area in northernmost Sweden. This is an area with a temperature close to the 0 OC mean annual isotherm. LÄS MER