Restoration thinning alters seed rain in long-leaf pine woodlands

Background/Question/Methods

Ecological restoration can have important impacts on populations and communities of interest, yet the outcomes of restoration are notoriously variable. Land-use legacies, such as former agricultural practices, may contribute to this variation by altering community composition and diversity. We experimentally evaluated the impacts of overstory thinning, a common restoration strategy in fire-maintained forest ecosystems, and how these impacts are modified by agricultural legacies for seed rain in long-leaf pine woodlands. Seed rain has important consequences for restoration by contributing to arrival, recruitment, and persistence of plant populations. We hypothesized that overstory thinning would increase seed rain by increasing resource availability (e.g. light and water) for understory plant populations, which can then in turn have an effect on fecundity of these populations. Further, we hypothesized that post-agricultural patches would have higher seed rain densities due to a greater proportion of ruderal species that produce many seeds. We established seed traps (n=504) in 126 one-hectare plots, which vary independently in land-use history (post-agricultural pine plantation or remnant long-leaf pine woodlands) and restoration treatment (overstory thinning or control). During the winter of 2012, we collected seeds from all traps and counted and identified all seeds to the most specific taxonomic level possible. 

Results/Conclusions

Our preliminary results show that restoration thinning, but not land-use history, affected seed rain by increasing  seed rain density (~53 seeds/0.6m2 in restored plots vs. ~14 seeds/0.6m2 in control plots), though richness of seeds was not influenced by restoration. We found no effect of land-use history or interaction between land-use history and restoration on seed rain density or seed species richness. These preliminary results suggest that restoration strategies, such as overstory thinning, can have important consequences for the levels of seed rain in a habitat patch and that land-use history does not affect these outcomes. Restoration could therefore be important for seed-limited populations and communities because of its effect on rates of seed arrival and subsequent plant recruitment.