Growing season nutrient dynamics of four reindeer forage species (Betula nana, Eriophorum angustifolium, Rumex acetosa and Vaccinium myrtillus) were studied in a mountainous sub-arctic landscape in N Sweden. Changes in nitrogen (N), phosphorus (P) and fibre (ADF) concentrations in [eaves and shoots were analysed (from a reindeer foraging perspective) along four ecological gradients significant to regional and local snowmelt regimes: season, oceanicity, attitude, and snow-patch retreat. N and P concentrations showed marked seasonal variations with peaks occurring from the middle of June to the end of July depending on species and snowmelt progression. The seasonal pattern for ADF concentrations, as well as differences between snowmelt regimes, were less consistent and showed large differences between species. N concentrations increased along snowmelt gradients at small (within snow-patches) and medium (along attitude gradients) spatial scales. Furthermore, variations in N concentrations were temporally and spatially scale-dependent, which underlines the importance of scale for understanding plant nutrient dynamics in sub-arctic and alpine systems, as well for plant-animal interactions. The greatest temporal and spatial differences in nutrient quality were observed early in the season, i.e., at the time of highest nutrient requirements for reindeer. Climate-induced changes of the start and the progress of the growing season may result in significant consequences to the development of calves and subsequently to the population demography of reindeer, mediated through spatial and temporal changes in the distribution of high quality food. These results provide basic knowledge for reindeer management in the tight of the ongoing global warming. (C) 2005 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.