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Medientyp:
E-Artikel
Titel:
Nutrient Limitation to Nitrogen Fixation in Young Volcanic Sites
Beteiligte:
Vitousek, Peter M.
Erschienen:
Springer-Verlag, 1999
Erschienen in:Ecosystems
Sprache:
Englisch
ISSN:
1432-9840;
1435-0629
Entstehung:
Anmerkungen:
Beschreibung:
<p> I used measures of<sup>15</sup>N natural abundance and of nitrogenase activity (acetylene reduction) to examine whether the supply of non-N nutrients limits rates of N<sub>2</sub>fixation on young volcanic substrates in Hawaii. Leaves of the dominant tree (Metrosideros polymorpha, a nonfixer) were strongly depleted in<sup>15</sup>N in control plots<tex-math>$(-10.8\ \text{to}\ -11.1‰)$</tex-math>. More than 5 y of repeated fertilization with P increased δ<sup>15</sup>N to -8.9 to<tex-math>$-9.9‰$</tex-math>, and the addition of all other essential plant nutrients (except N) together with P further increased<tex-math>${}^{15}{\rm N}\ \text{to}\ -8.1\ \text{to}\ -9.3‰$</tex-math>. This pattern is consistent with enhanced N<sub>2</sub>fixation, because newly fixed N would have a δ<sup>15</sup>N near<tex-math>$0‰$</tex-math>. 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 N<sub>2</sub>fixation in these young volcanic sites and thereby contributes to the maintenance of N limitation to primary production and other ecosystem processes. </p>