Phenology and growth of Papaver radicatum Rottb. was monitored over four summers (1990–1993) at 12 sites, along a dolomitic and a granitic altitudinal gradient (330 m a.s.l.–770 m a.s.l.) at Sverdrup Pass, central Ellesmere Island, Canada. The gradients provided substantial differences in environmental characteristics. Three of the four seasons (1990, 1991 and 1993) had more than 400 thawing degree‐days (TDD) in the valley, wh...

Passive open‐top devices have been proposed as a method to experimentally increase temperature in high‐latitude ecosystems. There is, however, little documentation on the efficacy of these devices. This paper examines the performance of four open‐top chambers for altering temperature at six sites in the Arctic and Antarctica. Most of the heating effect was due to daytime warming above ambient; occasional night‐time cooling bel...