Salix lanata ssp. richardsonii from open-tundra and streamside populations were studied at seven sites along a 100-km north–south transect following the Sagavanirktok River from the Alaskan arctic coast to the foothills of the Brooks Range. Mean July temperatures along this transect vary from 2.6 at the coast to 10 °C at the base of the foothills. Mean maximum heights of the sampled open-tundra willows increased from 10 ± 2 at the coast to 37 ± 8 cm at the southern end of the transect. Mean maximum heights of sampled streamside willows increased from 0 at the coast to 147 ± 25 cm. The mean maximum height of willows in both habitats showed very strong correlations with thawing degree-days. Mean growth-ring widths increased from 92 ± 20 at the coast to 188 ± 57 μm at the southern end of the transect and were also highly correlated with the temperature gradient. The results are discussed in light of other arctic studies of willow growth rings and Cantlon's system of vegetation subdivisions within the Alaskan arctic.
