Investigating the Seed Bank of a Wetland Plant Community in a Long-Term Mowing and Fertilization Experiment

Abstract

The seed bank of a plant community—the store of viable, dormant seeds below the soil surface—holds a legacy of its past composition and may have potential for restoration following habitat degradation. An ongoing 20-year fertilization and mowing experiment studies the plant community of a nutrient poor wetland in the coastal plain of North Carolina. The experiment is replicated on eight blocks and features a hydrology gradient that is caused by a drainage ditch. Since the start of the experiment, unmowed plots have become less diverse and are dominated by trees and shrubs. This long-term experiment provided the opportunity to explore the persistence of the seed bank through time. Soil samples from each treatment plot were collected and placed in a growth room to allow germination. The number of seedlings that emerged was recorded to test for the effect of fertilizer, mowing, and drainage on species richness and abundance of the seed bank and compare its composition to that of current and past aboveground vegetation. Multivariate statistics were used to look for treatment effects on the composition of the seed bank community. Fertilizer and drainage did not have a significant effect on the density or species richness of the seed bank, but it had a strong effect on its composition. In contrast, mowing had a significant positive effect on species richness and seed density but did not affect the composition of the seed bank. In comparison between the seed bank and the current aboveground vegetation composition, the mowed plots showed greater similarity, suggesting that the seed bank retains the species of the past plant community. As the aboveground vegetation changes, the seed bank may hold the ability to serve in future restoration projects.