Development and validation of rapid assessment indices of condition for coastal tidal wetlands in southern New England, USA

Abstract

Vegetation, soils, on-site disturbances, and watershed land use and land cover were assessed at 81 coastal tidal wetland sites using the New England Rapid Assessment Method. Condition indices (CIs) were derived from various combinations of the multi-dimensional data using principal component analyses and a ranking approach. Nested within the 81 wetlands was a set of ten reference sites which encompassed a range of watershed development and nitrogen loadings. The reference set of coastal tidal wetlands was previously examined with an intensive assessment, which included detailed measures of vegetation, soils, and infauna. Significant relationships were found between most of the rapid assessment CIs and the intensive assessment index. Significant relationships were also found between rapid assessment CIs and the developed lands in a 1-km buffer around the coastal wetlands. The regression results of the rapid assessment CIs with the intensive assessment index suggest that measures of vegetation communities, marsh landscape features, onsite marsh disturbances, and watershed natural lands can be used to develop valid CIs, and that it is unnecessary to make finer scale measurements of plant species and soils when evaluating ambient condition of coastal tidal wetlands in southern New England. However, increasing the survey points within coastal tidal wetland units when using a rapid assessment method in southern New England would allow for more observations of vegetation communities, marsh landscape features, and disturbances. Nevertheless, more detailed measures of hydrology, soils, plant species, and other biota may be necessary for tracking restoration or mitigation projects. A robust and standardized rapid assessment method will allow New England states to inventory the ambient condition of coastal tidal wetlands, assess long-term trends, and support management activities to restore and maintain healthy wetlands.

Evaluating indicators of marsh vulnerability to sea level rise along a historical marsh loss gradient

“…The most abundant species in the Blackwater marshes are S. americanus , S. alterniflora and S. patens (Figure 4). Of these, S. patens is considered a high marsh species (Bertness, 1991b; Smith, 2009; Wigand et al ., 2011; Raposa et al ., 2017) and S. americanus and S. alterniflora are considered low marsh species (Bertness, 1991b; Nyman et al ., 1994; Donnelly and Bertness, 2001), but these species do not show a clear abundance shift with increasing marsh loss (Figure 4) or with decreasing marsh surface elevation (data not shown). We hypothesize that clear abundance shifts with marsh loss are absent because they occupy elevations far below their optimum range, as flooding experiments of S. americanus and S. patens in the Blackwater marshes have demonstrated (Kirwan and Guntenspergen, 2012, 2015).…”

“…4). Spartina patens is considered as a high marsh species (Bertness, 1991b;Smith, 2009;Wigand et al, 2011;Raposa et al, 2017) and Schoenoplectus americanus and Spartina alterniflora are considered low marsh species (Bertness, 1991b;Nyman et al, 1994;Donnelly and Bertness, 2001), but these species do not show a clear abundance shift with increasing marsh loss (Fig. 4) or with decreasing marsh surface elevation (data not shown).…”

High nutrient loads amplify carbon cycling across California and New York coastal wetlands but with ambiguous effects on marsh integrity and sustainability

“…Soil respiration. Carbon dioxide efflux was measured in the low marsh at each study site during summertime peak respiration rates using a LiCor 8100 infrared gas analyzer outfitted with an opaque dome [30], with 10 cm PVC collars inserted in the soil approximately one hour before measurements were made. Incubations lasted three minutes, with observations of CO 2 concentration made every second.…”

“…However, as nitrate acts as a terminal electron acceptor, enhanced nitrate delivery to wetlands may enhance heterotrophic decomposition in concert with nitrate reduction (to N 2 or NH 4 + ) [28,29]. Enhanced decomposition is problematic for marsh survival because a reduction in belowground organic matter stocks can threaten resilience to sea level rise [30]. High nutrient levels have also been associated with increased soil sulfide levels in wetlands [16,31,32], suggesting that increased labile carbon inputs associated with eutrophication may fuel the reduction of sulfate to sulfide, which acts as a toxicant to wetland plants [33].…”

Mapping of biophysical and biochemical properties of coastal tidal wetland habitats with Landsat 8

“…9 Remote sensing techniques using satellite sensors supplies an economical and convenient method to onerous field work for assessing, monitoring, and protecting coastal tidal wetland and its dynamic variations in different resolutions and scale levels. 10 Over the past decade, developments in remote sensing techniques and rising availability of high-spectral and spatiotemporal resolution data have obviously improved our capacity to map properties of wetland habitats. 11 Multi-resolution spatiotemporal images from satellite such as MODIS, Landsat, and ASTER are available for free to the public and such sensors have been used in a few researches for the classification of wetland ecosystems.…”