Approximately 250,000 acres of longleaf pine (Pinus palustris) plantations have been established on former agricultural sites in the southern USA in the past decade, many if not most with a primary objective for wildlife management using prescribed fire. Restoration goals for productive longleaf pine ecosystems with quality wildlife habitat include the need for reintroduction of prescribed fire and for development of a groundcover of native grasses and forbs. This study examines the long-term effects of dormant and growing season burning on soil nitrogen(N) and carbon(C) in fourteen year-old stands of longleaf, factorialized with warm season grass groundcovers with and without N₂-fixing native legumes. Total N and C pools, soil organic N, and soil and pine foliar δ¹⁵N will be assessed over time to detect responses to N loss via burning and N additions via fixation. Although most sites initially have some residual fertility, soils are generally highly depleted in both organic matter and total N relative to mature native longleaf woodland soils. The soil pretreatment δ¹⁵N profile at 0-10cm, 10-20cm, and 20-30cm increases with depth with means of 6.2, 6.8 and 6.9 respectively. Soil and pine foliage (-3.0), and litter (-2.9) δ¹⁵N values from the plantations vary slightly from native woodlands. Legume foliar δ¹⁵N values range from -4 to -.25. Measures of soil δ¹⁵N may provide a useful technique for assessing changes in soil and vegetation pools of N and C with restoration treatments over time.