Inter-Planting Loblolly Pine with Nitrogen Fixing Nurse Trees on a Reclaimed Surface Mine in Virginia

In 1980, an experiment was established to study the effect of interplanting loblolly pine (Pinus taeda) with nitrogen-fixing nurse-trees. The study area was surface mined and reclaimed in 1979. In accordance with current reclamation regulations, the site was revegetated with an herbaceous ground cover which included perennial legumes. Loblolly pine was planted on a 3 m by 1.5 m spacing and interplanted with either 1) black locust (Robinia psuedoacacia), 2) black alder (A/nus glutinosa), or 3) no nurse-tree ( control treatment). After nine years, the growth of the pines was not improved by the nurse-trees. Soil nitrogen and forest floor litter nitrogen contents were about 10% higher in the nurse-tree treatments, but the additional nitrogen did not result in improved nitrogen nutrition for the pines as evidenced by foliar nutrient analysis. Apparently the herbaceous legumes provided enough nitrogen to serve the needs of the loblolly pine during this nine year study. Additional