The regional determining factors underlying inter-and intra-site variation of N-15 natural abundance in foliage, O horizon and mineral soil were investigated in eastern China. N-15 natural abundance values for these forest ecosystems were in the middle of the range of values previously found for global forest ecosystems. In contrast to commonly reported global patterns, temperate forest ecosystems were significantly more N-15-enriched than tropical forest ecosystems, and foliage delta N-15 was negatively correlated with increasing mean annual temperature and net soil N mineralisation in eastern China. Tight N cycling in forest ecosystems and the use of atmospheric N deposition by trees might underlie the delta N-15 distribution patterns in eastern China. The existence of mycorrhizal fungi and root distribution profiles in the soil may also influence the N-15 natural abundance patterns in forest ecosystems of eastern China.