Abstract:The physical characteristics and CO 2 concentrations of snow cover in the western Canadian arctic were examined at sites with dierent landscape forms (valley¯oor, hillslope, plateau). The greater exposure of plateau snow cover to blowing snow results in dierences in the structure of the snow cover and dierent snow strata compared with snow covers on the other landscape forms. Both higher in-pack concentrations of CO 2 and the largest vertical CO 2 concentration gradients were found in plateau snow cover, the smallest in the deeper hillslope and valley snows. CO 2 gradients in all landscape snow covers followed two patterns, i.e. where concentrations at the soil±snow interface are higher than those just below (5 cm) and the snow±atmosphere interface and vice versa. The latter pattern is due to the transport of the gas from the lower levels to the upper levels of the snowpack by wind-induced advection (windpumping) and is indicative of non steady-state, nondiusive processes. These latter processes should thus be considered in any studies on CO 2¯u xes from Arctic soil where snow cover topography and winds are conducive to windpumping and where concentration gradients resulting from diusive processes have not been clearly identi®ed.

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ABSTRACT. The location, nature, and magnitude of some environmental changes associated with the introduction of a road across a muskeg in the discontinuous permafrost zone are identified from examination of near-infrared Landsat images. Impedance of natural surface drainage by the presence of a roadbed is hypothesized to transmit upstream hydro-thermal changes through the muskeg terrain, which in turn cause change in the muskeg vegetation community. Differences among the near-infrared spectral reflectances of fen, black spruce bog, and Sphagnum bog communities are found sufficiently large for use as indices of differences in the actual biophysical natures of the muskegs.Key words: environmental impact, northern Canada, muskegs, hydrology, Landsat interpretation, permafrost, road design &SUMÉ. L'ktude d'images de Landsat presque infrarouges r6vvble l'emplacement, le genre et l'amplitude de certains changements dans I'environnement associes iI la construction d'une route B travers un marais dans une zone 21 pergklisol discontinu. L'auteur prbente une hypothk selon laquelle l'assiette de la chaussk ferait obstacle au drainage de surface normal, causant ainsi des variations dans la vtgktation du marais. Les diffkrences en rkflectance spectrale presque infrarouge entre la terre markageuse, le markage d'kpinettes noires et le markcage de sphaigne sont d'une importance suffisante il servir d'indice dans la nature biophysique vtritable du marais.