Root and leaf phenology of Scandinavian subarctic plant communities, 2008-2009

At each field site, eight replicate 1 x 1 m plots were established in five subarctic vegetation communities representative of the wider landscape, including birch forest, forest margin, tall and dwarf shrub tundra communities and sedge lawns. Each plot had a mini-rhizotron (0.3x0.7 m length of 70 mm diameter clear acrylic tubing) installed at 45o and shoots of the dominant plant species tagged with numbered cable ties. In 2008 in Kevo and 2009 in Abisko, length of all tagged shoots was recorded approximately weekly during the growing season, and a weekly 360o scan of all mini-rhizotrons taken with a CID-600 root scanner (CID Bioscience, Camas, Washington, USA). Root length was obtained from the scanned images by manually digitising visible roots using MapInfo Professional v. 8.0 software (Pitney Bowes Business Insight, New York, USA). Percentage cover of all species was estimated once at peak biomass in early August by a single surveyor, using a 0.75 x 0.75 m quadrat placed over each mini-rhizotron. Soil temperature at 5 cm depth was obtained from one TinyTag data logger (Gemini Data Loggers (UK) Ltd, Chichester, UK) per community, recording at 30 minute intervals. Additional soil temperature measurements at 5, 10, 15 and 20 cm depth were made weekly using a hand-held probe (Testo Ltd, Alton, UK). For further details of all measurements and data processing steps, see supporting documentation.