Hardwood Species Show Wide Variability in Response to Silviculture during Reclamation of Coal Mine Sites

Abstract

Coal is a significant energy source for the United States, and reclamation of surface mined lands is required under the Surface Mining Control and Reclamation Act of 1977. Reforestation of mined lands is challenging due to soil substrate properties including soil compaction, herbaceous competition, and animal browse, necessitating silvicultural treatments to help overcome such limiting factors. We investigated the field performance of black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.), and swamp white oak (Quercus bicolor Willd.) planted on two mine reclamation sites in southern Indiana, USA, and evaluated the interactions of nursery stocktypes (container and bareroot), herbicide application, and tree shelters. Two-year survival averaged 80% across all species and stocktypes. Container stocktype had greater relative height and diameter growth (i.e., relative to initial size at planting), whereas bareroot had greater absolute height and diameter growth corresponding to initial stocktype differences. Shelter use increased height growth and reduced diameter growth across both stocktypes. Swamp white oak (Q. bicolor) had the highest survival rate and field performance regardless of silvicultural treatment, whereas red oak (Q. rubra) and black walnut (J. nigra) showed strong early regeneration responses to silvicultural treatments. Container seedlings showed promise as an alternative to bareroot seedlings to promote early growth on mine reclamation sites. Species-specific responses documented here indicate the need to consider the ecology and stress resistance of target species in developing cost-effective silvicultural prescriptions.