We developed a multiple-indicator approach to evaluate differences in soil N availability across sites and between larch monoculture and mixed stands paired at three sites (Daxinganling, Maoershan, and Qingyuan) in northeastern China. The selected indicators were foliar %N, soil C/N, soil inorganic N, foliar δ¹⁵N, and δ¹⁵N of bulk soil, ammonium, and nitrate in the soil profiles.