15N NATURAL ABUNDANCE IN WOODY PLANTS AND SOILS OF CENTRAL BRAZILIAN SAVANNAS (CERRADO)

We measured the 15N natural abundance values of 320 individuals belonging to 45 different plant species of the Brazilian cerrado. We also determined δ15N of soil nitrogen as a function of soil depth. Our purpose was to test the hypothesis that N-limited cerrado would have a large range of plant δ15N values, similar to patterns seen in northern high-latitude ecosystems. Foliar δ15N values did demonstrate the large range found in some other N-limited ecosystems, varying from −5‰ to +7.9‰. Significant variability within individual species was also seen across cerrado community types. Several factors contributed to this variability, including the presence of N-fixing legumes, associations with mycorrhizal fungi, δ15N variability of soil organic matter with depth, fire events, and the seasonality of N-immobilization and mineralization processes in cerrado soils.