Studies on Structure in Plant Communities: II. The Structure of Some Dwarf-Heath and Birch-Copse Communities in Skjaldfannardalur, North-West Iceland

Abstract

During the summer of 1965 an ecological expedition was made to a recently de-glaciated valley in north-west Iceland in order to study dwarf-heath and birch-copse communities developed near a large ice-cap, Drangajokull, which is located some 50 miles (80 km) south of the Arctic Circle (see Fig. 1). The study area was located within the valley and adjoining plateaux surfaces of Skjaldfannardalur (660 00' N, 22? 15' W), which runs north-eastwards between Isafjardardjup and Drangajokull; the valley rises from sea-level to an altitude of 1380 ft (420 m) at its north-eastern extremity, which is some 16 miles (20 km) from the sea, and is incised into relatively uniform material of the Tertiary Basalt plateau. Although the climate of Skjaldfannardalur is reputed to have ameliorated during the last 30 years, the winter climate at least is still severe and temperature inversions can cause ground frosts even during high summer. The area is also periodically subjected to considerable drying winds, which blow directly over Drangajokull from the north and east, and heavy snow-falls are experienced from November through to March, with snowpatches persisting on many south-westerly slopes through the greater part of the summer. Some indication of the severity of the climate may be gained by examining meteorological data from the nearby station at Aedey (66? 06' N, 22? 40' W), which is situated some 5 m above sea level (see Table 1); the climate of the hinterland of Skjaldfannardalur is more severe but otherwise comparable with that experienced at Aedey. It seemed likely that the vegetation structure apparent in Skjaldfannardalur was controlled to some extent by climatic features of the environment; accordingly preliminary qualitative examination of the various communities was followed by a more detailed quantitative analysis of the structural make-up of these communities in relation to certain measured aspects of the physical environment experienced in the dale. In order to set this detailed examination in a broader context a preliminary description of the various communities is presented below; further qualitative descriptions are available in Steindorsson (1946).