Does the removal of invasive nitrogen-fixing black locust in a pine-oak community ensure a successful return to pre-invasion soil characteristics?

The black locust (Robinia pseudoacacia) is a highly invasive, nitrogen-fixing plant. Black locust trees increase soil nitrogen concentrations, supplement soil nutrient pools, and enhances the rates of nitrogen transformations, all of which favor the growth of other non-native plant species and contributes to lower plant species diversity. In the Albany Pine Bush Preserve, black locust has invaded the globally rare pitch pine—scrub oak barrens community. Restoration has been initiated to remove black locust stands throughout the preserve in hopes of protecting the rare plant and animal species that reside there. The purpose of this study is to determine if the restoration of black locust stands ensures a successful return to preinvasion soil characteristics. Initially soils were collected from three different plots: pine-oak, black locust, and restored. Soils were then assessed for nutrient content, nitrogen availability, and soil fertility. To gauge soil fertility, plant growth experiments were conducted in the Union College greenhouse using three native perennial grasses. Plant growth results showed that there was a significant difference between pine-oak soils and both black locust and restored soils. Plants grown in the pine-oak soil treatments had the greatest amount of biomass with restored and black locust trailing behind. There was no significant difference between black locust and restored soils. Nutrient content and nitrogen availability results showed that black locust soils have the greatest nutrient content and nitrogen availability, restored soils have intermediate values, while pine-oak soils have the lowest values. Restoration efforts in the Albany Pine Bush Preserve appear to have been successful as restored plots display soil characteristics prior to the invasion of the black locust