This study examines the influence of fire suppression (>10years) upon δ¹⁵N profiles in a mature longleaf pine (Pinus palustris) ecosystem. The δ¹⁵N profiles of a replicated burned and unburned stand were determined in litter, soil, and tissues of N fixing legumes and reference plants including increment cores extracted from pines in burned and unburned plots. Pine foliage, litterfall and litter δ¹⁵N values from burned stands are -3, -3.5 and -3 respectively. Soil δ¹⁵N values from burned plots increase with depth from 4.5 to 8.5, but fire suppression significantly decreased values from 2.5-30cm depths. Reference non-nitrogen fixing plants ranged in value from -3.0 to -4.0, and legumes are significantly different, ranging from -.5 to -1.8. The δ¹⁵N values in pine wood increment cores are not significantly different between burned and unburned treatments, but outer-wood (3-10 years old) and inner-wood (16-23 years old) are significantly different, -2.1 and -1.7 respectively. This indicates that internal physiological processes determined δ¹⁵N of tree rings rather than fractionation due to soil processes associated with fire suppression.