Alpine plants show species-level differences in the uptake of organic and inorganic nitrogen

As an estimate of species-level differences in the capacity to take up different forms of N, we measured plant uptake of N-15-NH4+, N-15-NO3- and N-15, [1]-C-13 glycine within a set of herbaceous species collected from three alpine community types. Plants grown from cuttings in the greenhouse showed similar growth responses to the three forms of N but varied in the capacity to take up NH4+, NO3- and glycine. Glycine uptake ranged from approximately 42% to greater than 100% of NH4+ uptake; however, four out of nine species showed significantly greater uptake of either NH4+ or NO3- than of glycine. Relative concentrations of exchangeable N at the sites of plant collection did not correspond with patterns of N uptake among species; instead, species from the same community varied widely in the capacity to take up NH4+, NO3-, and glycine, suggesting the potential for differentiation among species in resource (N) use.