Historical tidal forest composition and contemporary woody recruitment following dam removal from a Mid-Atlantic Coastal Plain tidal freshwater wetland

Background/Question/Methods

The titled research is truly “ecological science at the frontier” and timely with respect to the celebration of the ESA Centennial.  Tidal freshwater forest restoration along the Mid-Atlantic Coastal Plain, specifically after dam removal, has been unexplored to date.  This research was a mensurative exploration of pre-dam forest composition, as well as post-dam edaphic and microtopographical attributes and woody species recruiting along a narrow ecotone of a 29.3-ha tidal freshwater wetland.  It was suspected that the ≈65-year-old historical forest and ≈7-year-old contemporary forest would differ in terms of community dominants, and that species diversity and stem density would be a function of key environmental variables quantified along a narrow ecotone.  

 Results/Conclusions

Pre-dam and post-dam forest compositions were dissimilar in terms of dominant species (Fraxinus spp. vs. Liquidambar styraciflua, respectively), species diversity (15 spp. vs. 40 spp.) and stem density (200 stems ha⁻¹ vs. 11,009 stems ha⁻¹).  While pre-dam environmental conditions were unknown, post-dam edaphic water content, organic matter, redox potential and microtopography differed significantly across tidal sites but were less variable in non-tidal sites.  Shifts in the contemporary woody community composition and concomitant increases in stem density and seedling:sapling ratios along an elevation gradient was likely a function of significant changes in microtopography and edaphic attributes. Developing ecotones which offer variable microtopography may be extremely important for successful natural woody recruitment after dam removal from a tidal freshwater system.  These estimates of temporal and spatial recruitment sequences and community composition of the historical forest may have implications for variations in woody stand development and biogeochemical fluxes in the context of potential impacts of sea-level rise.