PATTERNS OF PLANT-DISTRIBUTION WITHIN 2 POLAR DESERT LANDSCAPES

Although most polar deserts are biologically very barren, there are ex ceptions. To determine the general pattern of plant distribution from an ice cap to the lower edge of a plateau, two transects were sampled, one each 500 to 720 m above Alexandra Fiord, Ellesmere Island and 350 to 685 m above Truelove Lowland, Devon Island. Where soil surfaces ar e moist much of the summer, there is a greater floristic richness, a g reater percent cover of cryptogams and vascular species, and the devel opment of a cryptogamic crust on both dolomite and granite-derived soi ls. In addition, the degree of soil churning, the coarseness and type of substrate, and soil nutrient levels are important at the local scal e. The limited data indicate that temperatures are higher at these loc ations than one would expect from normal lapse rates. The sporadic pre sence of two or three woody species at 350 to 550 m is further indicat ion of relatively mild conditions compared with most polar desert land scapes at these latitudes where woody species are absent.