Nitrogen utilization by Hylocomium splendens in a boreal forest fertilization experiment

• 1. Nitrogen uptake in the terricolous bryophyte Hylocomium splendens (Hedw.) B.S.G. was studied in a boreal forest long-term N-treatment experiment including control plots, N-addition plots (50 kg N ha(-1) year(-1) for 8 years) and recovery plots (50 kg N ha(-1) year(-1) for 5 years and thereafter no N addition for 3 years). 2.A main objective was to explore whether the N treatments changed bryophyte uptake of different inorganic and organic N forms. In addition, we estimated the contribution of N from throughfall precipitation to the bryophyte N supply. 3. The results demonstrated that bryophyte N uptake was similar in all the long-term N-treatment plots. Hylocomium splendens took up more N-15 labelled NH4+ than NO3- or glycine when these N forms were applied in situ by the spraying of solutions with N concentrations similar to those in precipitation. 4. Analysis of the precipitation collected beneath the closed tree canopy from late May to early October revealed that it contributed 2.0 kg N ha(-1) during the period studied, distributed between NH4+ (78%), amino acid N (17%) and NO3- (5%). 5. The study highlights that, in addition to analyses of NH4+ and NO3- (normally included in standard environmental monitoring of precipitation), analysis of amino acid N must be performed to account fully for the precipitation N input to bryophytes in boreal forest ecosystems.

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