Tree productivity is limited by soil nitrogen (N) stocks in the active layer on permafrost regions. Direct uptake of amino acids by plants is well-known to mitigate slow N mineralization in boreal forest soils. However, amino acid hypothesis could not fully meet N demand of black spruce trees on permafrost-affected soils. We test another hypothesis that black spruce could utilize urea directly. Using root uptake experiment after spike of mixture solution (13C, 15N-glutamic acid, 15N-urea, 15N-ammonium, 15N-nitrate) in northern Canada, we found that black spruce trees could uptake urea as well as amino acids directly. This is consistent with urea accumulation in mineral soil horizons on permafrost table, where microbial N mineralization is retarded. The other plants or bryophyte compete with amino acids but not urea. Since the other black spruce trees on deeper active soil layer rely on amino acids and inorganic N, urea uptake strategy is specific to black spruce trees on shallow permafrost table. The root expansion on hummocky microrelief provides opportunity for leaning trees to access urea. The direct urea uptake could be one of strategy of black spruce trees to mitigate N limitation in permafrost-affected hummocky soils.