Print PageThe development of plant canopy features is often considered to be a sign of successful coastal marsh restoration, but a robust plant canopy may not correspond with the recovery of other ecosystem attributes such as nutrient retention or faunal assemblages. Furthermore, construction designs that incorporate different soil sources and elevation gradients can also influence the ecosystem-level characteristics of a restored marsh. The objectives of our study were to (1) evaluate whether plant canopy development corresponded with the recovery of ecosystem attributes and (2) determine the influence of construction design on species- and ecosystem-level characteristics in restored and reference areas within a brackish marsh in the Lower Neches Wildlife Management Area in Texas, USA. The study site included a reference marsh and four types of restored marshes that were constructed in spring 2008. The restored areas consisted of mounded or terraced formations built from on-site soil or from off-site dredge material. We conducted comprehensive surveys of the biotic and abiotic characteristics of the emergent marshes and aquatic habitats in restored and reference areas in June 2009 and September 2010.
Results/Conclusions
At the emergent plant level, each construction approach successfully yielded similar percent cover, stem density, and aboveground biomass as the reference area. In both 2009 and 2010, Discriminant Function Analyses (DFA) of visible emergent plant characteristics suggested that species richness was higher in the reference area but all other plant canopy features were similar among areas. The DFA classification success was generally less than 60%, suggesting substantial overlap among reference and restored areas. However, DFA of a more complex suite of plant, soil, and aquatic characteristics in 2009 revealed that the reference area had more sand and higher soil nitrogen and carbon content relative to all restored areas. Classification success was generally greater than 70%, suggesting that at the ecosystem level, each restoration approach was distinct from the others. DFA of plant, soil, and aquatic characteristics in 2010 revealed fewer abiotic differences among areas, and classification success decreased to less than 67%, suggesting that the different restored areas were becoming less distinct from each other over time. Overall, at the ecosystem level, each of the restoration approaches was unique, and none of them resembled the reference area. As the suite of measured variables increased in complexity, so did the dissimilarity between the reference and restored areas, but these differences diminished over time as the restored areas developed.
