Blar i forfatter "Tømmervik, Hans"

Viser treff 21-23 av 23

    • Use of unmanned aircraft systems (UAS) in a multi-scale vegetation index study of arctic plant communities in Adventdalen on Svalbard 

      Tømmervik, Hans; Karlsen, Stein-Rune; Nilsen, Lennart; Johansen, Bernt; Storvold, Rune; Zmarz, Anna; Beck, Pieter S.; Høgda, Kjell Arild; Goetz, Scott; Park, Taejin; Zagajewski, Bogdan; Myneni, Ranga B.; Bjerke, Jarle W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
      Use of Unmanned Aircraft Systems (UAS) gives the opportunity to carry out research with a re-duced environmental footprint. Unmanned aircraft, including both fixed wing and multi rotor types (helicopters) allow us to collect very high resolution image data for vegetation mapping without the need for any personnel walking into the site and thereby potentially disturbing the sensitive Arctic ecosystems. ...

    • Using Ordinary Digital Cameras in Place of Near-Infrared Sensors to Derive Vegetation Indices for Phenology Studies of High Arctic Vegetation 

      Anderson, Helen; Nilsen, Lennart; Tømmervik, Hans; Karlsen, Stein Rune; Nagai, Shin; Cooper, Elisabeth J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      To remotely monitor vegetation at temporal and spatial resolutions unobtainable with satellite-based systems, near remote sensing systems must be employed. To this extent we used Normalized Difference Vegetation Index NDVI sensors and normal digital cameras to monitor the greenness of six different but common and widespread High Arctic plant species/groups (graminoid/Salix polaris; Cassiope tetragona; ...

    • Where do the treeless tundra areas of northern highlands fit in the global biome system: toward an ecologically natural subdivision of the tundra biome 

      Virtanen, Risto; Oksanen, Lauri Kalervo; Oksanen, Tarja Maarit; Cohen, Juval; Forbes, Bruce C.; Johansen, Bernt; Käyhkö, Jukka; Olofsson, Johan; Pulliainen, Jouni; Tømmervik, Hans (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-15)
      According to some treatises, arctic and alpine sub-biomes are ecologically similar, whereas others find them highly dissimilar. Most peculiarly, large areas of northern tundra highlands fall outside of the two recent subdivisions of the tundra biome. We seek an ecologically natural resolution to this long-standing and far-reaching problem. We studied broad-scale patterns in climate and ...