the relationship between plant growth and nitrogen supply is frequently used in growth models to predict growth performance under global climate change scenarios. however, the relationship may be changed under elevated [co2]. furthermore, plant responses to nitrogen supply may be modified by n-p-k ratio. researchers using climate envelope models predict that boreal tree species will migrate northward during progress of the global warming associated with increasing atmospheric co2 and changes in precipitation. however, changes in photoperiod and nutrient supply associated with the northward migration to higher latitudes may influence survival and growth of the migrated plants.