The purpose of this paper was to examine the vegetative, sedimentary, nekton and hydrologic conditions prerestoration and the initial 2 years post-restoration at a partially restricted macro-tidal salt marsh site. Replacement of the culvert increased tidal flow by 88%. This was instrumental in altering the geomorphology of the site, facilitating the creation of new salt marsh pannes, expansion of existing pannes in the mid and high marsh zones, and expansion of the tidal creek network by incorporating relict agricultural ditches. In addition, the increase in area flooded resulted in a significant increase in nekton use, fulfilling the mandate of a federal habitat compensation program to increase and improve the overall availability and accessibility of fish habitat. The restoration of a more natural hydrological regime also resulted in the die-off of freshwater and terrestrial vegetation along the upland edge of the marsh. Two years post-restoration, Salicornia europea (glasswort) and Atriplex glabriuscula (marsh orache), were observed growing in these die-back areas. Similar changes in the vegetation community structure were not observed at the reference site; however, the latter did contain higher species richness. This study represents the first comprehensive, quantitative analysis of ecological response to culvert replacement in a hypertidal ecosystem. These data will contribute to the development of long-term data sets of pre-and post-restoration, and reference marsh conditions to determine if a marsh is proceeding as expected, and to help with models that are aimed at predicting the response of marshes to tidal restoration at the upper end of the tidal spectrum.
We numerically classified tidal wetland vegetation and determined the relationships between variation in plant species composition and environmental factors. Sampling was conducted at eight sites along a range of tidal magnitudes (<2 to >14 m). Cluster analysis revealed seven distinct salt or brackish marsh plant associations, usually dominated by a single graminoid species. Redundancy analysis showed continuous variation among community units and identified inundation time, elevation, soil salinity, and organic matter content as key correlates of plant community patterns. Associations detected were similar to those found in New Brunswick’s Bay of Fundy and Northumberland Strait wetlands, and to those farther south in northern New England, but two new brackish associations were also identified within this study (Juncus balticus Willd. – Festuca rubra L. and Spartina pectinata Link). Although elevation is understood to drive vegetation types in salt marshes in the region, here we show that salinity can differentiate vegetation types at the same elevation. These data provide a quantitative baseline and allow for better predictions of tidal wetland ecological restoration trajectories in Nova Scotia.
Salt marshes provide many important ecosystem services, and interest in their restoration is growing in response to climate change. In Maritime Canada, salt marsh restoration projects have focused on restoring tidal flow without planting. Over time, these sites can show persistent deficits in vegetation diversity. We evaluated six techniques for encouraging revegetation (plugs, field transplants, seed, wrack, tilling, and no planting) with eight native species (Carex paleacea, Juncus gerardii, Limonium carolinianum, Plantago maritima, Poa palustris, Solidago sempervirens, Sporobolus alterniflorus, and Sporobolus michauxianus) at two Bay of Fundy salt marsh restoration sites. Community recovery and plant performance (growth rate, summer and winter survival, and health) were monitored over 2 years. Planting plugs produced the highest abundance of perennial halophytes over both years with high survival rates (76.4% AE 0.02 SE), whereas plants transplanted from adjacent sites had higher mortality and slightly lower cover. All planted species survived and grew. Growth rate, health, and winter survival were all more strongly related to site than planting technique, indicating that location was more important to success than technique. We found evidence that differences in elevation, inundation, soil salinity, and soil nutrients at each site may explain these differences in performance. Plugs and field transplants may both be useful for restoration in the future and mixing methods to capitalize on respective strengths may produce best results when planting. Our results also highlight the need to tailor planting plans to individual sites as plants may respond uniquely in different situations.
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