Summer Air Temperature and Number of Vascular Species in Arctic Canada

Exceptionally high correlations (r=0.90-0.97) between number of vascular species and various indices of summer warmth at 38 localities in the Canadian Arctic support Young's contention that summer thermal regime is the most important ecological factor controlling the broad zonation of arctic flora. Highest correlations (r=0.97) are with July mean temperature and mean number of degree-days above 0 degrees C in July. Regression equations relating July mean temperature and number of species indicate a diversity gradient of about 25 species per degree. These equations provide estimates of species numbers or July temperatures in areas with poor climate or botanical data and may also be used to identify anomalous conditions.Key words: vascular species, floristic diversity, Canadian ArcticMots clés: espèce vasculaires, diversité florale, Arctique canadie