Sökning: "Subarctic ecosystems"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden Subarctic ecosystems.

1. 1. The hidden life of plants : fine root dynamics in northern ecosystems

   Författare :Gesche Blume-Werry; Roland Jansson; Ann Milbau; Scott D. Wilson; Isla Myers-Smith; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Arctic; belowground; boreal; climate change; fine roots; heath; meadow; minirhizotron; permafrost; phenology; plant community; root biomass; root growth; root litter; root production; subarctic; tundra;

   Sammanfattning : Fine roots constitute a large part of the primary production in northern (arctic and boreal) ecosystems, and are key players in ecosystem fluxes of water, nutrients and carbon. Data on root dynamics are generally rare, especially so in northern ecosystems. LÄS MER

3. 2. 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

4. 3. Mechanisms of below-ground carbon cycling in subarctic ecosystems

   Författare :Maria Olsrud; Institutionen för naturgeografi och ekosystemvetenskap; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; cartography; climatology; Fysisk geografi; geomorfologi; marklära; kartografi; klimatologi; pedology; geomorphology; Physical geography; subarctic tundra; phosphorous mobilization; organic acids; open top chamber experiment; 15N natural abundance; Ericoid mycorrhizas; global change; 14C pulse-labelling; Carbon allocation;

   Sammanfattning : Some components of the below-ground carbon (C) cycle in terrestrial ecosystems are still poorly understood. A better understanding will be necessary to predict adequately the impacts of global change factors on C cycling and storage, especially in high-latitude ecosystems, where much of the C is stored below-ground. LÄS MER

5. 4. 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

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