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 15NNH4 +, 15N-NO3 – and 15N, [1]-13C 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.