Description: Nutrient availability is one of the most important factors controlling Arctic plant productivity. It is also sensitive to climate change, with increased nitrogen (N) mineralization arising from warmer soils and deeper snow. However, warming also tends to reduce snow cover duration, leading to antagonistic effects of climate change on mineralization. Furthermore, since snow melt is also a trigger for seasonal nutrient pulses, changes to snow melt timing may alter seasonal availability to plants. To investigate the impacts of environmental conditions on ecosystem nutrient availability and seasonal dynamics, we undertook regular, high-frequency measurements of soil extractable and plant N and phosphorus (P) concentrations along with winter and summer N and P mineralization rates along a sub-Arctic catchment representing a gradient in temperature, snow melt timing and vegetation composition. Our data show that a delay in snow melt timing of 11 days did not alter the seasonal dynamics of soil or leaf N and P concentrations. Net N mineralization, however, was highest at the warmest site and at the site with the most productive vegetation, while P was strongly immobilized at all sites, both in winter and summer. N:P ratios suggest that plants were generally P limited at all sites, probably due to strong P immobilization. Our data suggest that where warming and resulting vegetation change increase net N mineralization rates, in combination with strong P immobilization this may impose greater P limitation, possibly limiting the extent to which Arctic ecosystems can increase productivity under warming.