changes in atmospheric co2 concentration ([co2]) and temperature may influence nutrient resources and how boreal species respond to their environment. the effects of increased [co2] on plants are generally positive but can be very complex because of interactions with soil temperature and nutrient availability on physiology, growth, root characteristics and biomass production. the issue is further complicated because species can respond differently to the interactive effects of these factors. two experiments were conducted to determine how soil temperature, nutrient supply and inter-plant root interactions affect gas exchange, morphology, root traits and growth of black spruce (picea mariana [mill.] b.s.p.) and white spruce (picea glauca [moench] voss.) seedlings.