Minimum Area and Cover-Abundance Scales as Applied to Polar Desert Vegetation

Polar desert vegetation with 5% cover or less was measured on terraces and a plateau surrounding Sverdrup Pass (79°N), central Ellesmere Island, N.W.T., Canada. The aim of the study was to determine the most efficient method for plant diversity and cover assessment in extremely sparse polar desert plant communities. Minimum area was measured using, independently, the nested plot and the random quadrat techniques in five polar desert stands. The Species diversity: Area relationship (SIA) was best described by the Fisher logarithmic model. The minimum area determined for the stands ranged from 10 to 25 m2. The total vascular species diversity among the sites varied from 6 to 22. Cover values, precisely measured by the grid-quadrat technique, were transformed to four abundance scales: Braun-Blanquet, Domin-Krajina, and two further refinements of Domin-Krajina scale. These modifications were designed to increase the resolution in the low-cover portion of the scale, and substantially improved the accuracy of the cover determination. The author suggests the use of a modified Domin-Krajina abundance scale in a stratified random sampling of an area at least equal to the minimum area. This allows for a more expedient yet still adequately accurate assessment of the extremely low cover vegetation and ensures that minute plants will not be overlooked or their cover grossly overestimated.