Spatial changes in tree and upland tundra cover in response to a compl
ex environmental gradient and to landscape factors were investigated i
n the high subarctic forest-tundra of NW Canada. Vegetation and terrai
n studies provided ground truth for a grid of 1314 air photos which co
vered 24 % of the Canadian high subarctic and some of the adjacent low
subarctic and low arctic. Across the high subarctic, gradual spatial
change in % cover of tree and upland tundra vegetation is typical at b
oth high and low cover values, with more rapid change occurring at int
ermediate cover. Cover gradients of zonal tree and tundra vegetation i
n the forest-tundra region in general follow a sigmoid pattern. Tundra
and tree patch sizes increase in area and variability with higher tun
dra and tree cover, respectively.