Floristic sectors characterize the considerable east-west floristic variation within the subzones. The more northern Arctic bioclimate subzones have a relatively consistent core of Arctic plant species that occur around the circumpolar region. Further south, local east-west variation is related to a variety of factors, including different paleohistories and the greater climatic heterogeneity. Large north-south trending mountain ranges, primarily in Asia, have also restricted the exchange of species between parts of the Arctic. Yurtsev (1994) delineated six floristic provinces and 20 subprovinces and discussed their characteristics. The Pan-Arctic Flora project (Elvebakk et al. 1999) has accepted Yurtsev's division in principle, but PAF uses the term "sectors" to replace Yurtsev's "subprovinces" and has grouped the sectors somewhat differently. The main change is a new North Atlantic group and the inclusion of Yurtsev's Baffin-Labrador Province as part of the North Atlantic group. The sectors described here are based on Elvebakk et al. (1999). Readers interested in panarctic floristic variation within the subprovinces should read Yurtsev (1994) (highly recommended).
The Circumpolar Arctic Vegetation Map (CAVM) project at University of Alaska Fairbanks has developed a number of map layers that describe the vegetation across the high north. This map layer shows how scientists have categorized different regions of the Arctic according to different growing conditions.