ABSTRACT
I used measures of 15N natural abundance and of nitrogenase activity (acetylene reduction) to examine whether the supply of non-N nutrients limits rates of N2 fixation on young volcanic substrates in Hawaii. Leaves of the dominant tree (Metrosideros polymorpha, a nonfixer) were strongly depleted in 15N in control plots (–10.8 to –11.10/00). More than 5 y of repeated fertilization with P increased δ15N to –8.9 to –9.90/00, and the addition of all other essential plant nutrients (except N) together with P further increased 15N to –8.1 to –9.30/00. This pattern is consistent with enhanced N2 fixation, because newly fixed N would have a δ15N near 00/00. Assays of nitrogenase activity in the experimental plots demonstrated that potential N fixation associated with nonvascular plants and with tree and fern litter were increased significantly by additions of P and by the combined nutrient treatment; when these were added together, the increase in nitrogenase activity was 6- to 11-fold over control plots. The supply of P and other weathering-derived nutrients constrains rates of N2 fixation in these young volcanic sites and thereby contributes to the maintenance of N limitation to primary production and other ecosystem processes.
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Received 7 January 1999; accepted 3 May 1999.
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Vitousek, P. Nutrient Limitation to Nitrogen Fixation in Young Volcanic Sites. Ecosystems 2, 505–510 (1999). https://doi.org/10.1007/s100219900098
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DOI: https://doi.org/10.1007/s100219900098