James E. Perry

Use of created Wetland delineation and weighted averages as a component of assessment

Forested wetland creation for compliance with Section 404 of the Clean Water Act is increasing dramatically throughout the Mid-Atlantic region of the United States. However, no quantitative data are available regarding the effectiveness of past forested wetland creation efforts in this region, and no quantitative assessment techniques for evaluating success have been developed. Created wetlands may lack sufficient time for soil formation; however, colonizing vegetation and hydrology may be considered indicators of existing conditions. Hydrology monitoring is expensive, time-consuming, and highly variable over short time periods. This study was designed to test the hypothesis that one parameter (vegetation) could be used to evaluate early site conditions following wetland creation. We attempt to show the advantages and disadvantages of using vegetation to calculate percentage “wetland” and “upland” as an early monitoring tool. Calculations were made using the 1989Federal Manual for Identification and Delineation of Jurisdictional Wetlands, colonizing vegetation weighted average, site moisture estimates, and comparisons with an adjacent reference wetland. Percentage “wetland” and “upland” estimates were similar whether vegetation alone or vegetation in combination with hydrology was used in calculations. Vegetation colonizing the site may respond to both soil and hydrology and may provide an early indication of conditions within created wetlands. The findings of this study suggest that calculating plot-weighted averages and comparison with pre-impact wetland vegetation (or an adjacent reference wetland) may be a useful component of a monitoring scheme for certain created wetlands.

Temporal changes in the vegetation pattern in a tidal freshwater marsh

Temporal changes in vegetation patterns of Chesapeake Bay wetlands have been poorly documented. Data from a 1987 vegetation analysis of a Chesapeake Bay tidal freshwater marsh were compared to those of a vegetation study completed in 1974. Changes in the vegetation pattern were calculated using species importance values and a species diversity index. Comparison of the 1987 and 1974 results shows no significant difference in species diversity index. However, there was a significant difference in species contribution to the index.Spartina cynosuroides, an oligohaline species that was not among the dominant species listed in the 1974 study, had the fourth highest importance value in this study. The change in dominant species composition of the marsh may reflect a directional shift from tidal freshwater toward oligohaline conditions.

Assessing anthropogenic and natural impacts on ghost crabs (Ocypode quadrata) at Cape Hatteras National Seashore, North Carolina.

Abstract This study explores impacts of off-road vehicles on ghost crab populations as a measure of impact from recreational beach use on two beaches of the Cape Hatteras National Seashore and assesses the effectiveness of several alternatives for the use of off-road vehicles (ORVs) on the beach. Ghost crab population size and density have been used as indicators of the environmental quality of beaches and dunes. Data on the creation of an “ORV corridor” in which ORVs can drive on the landward portion of the berm, but not on the beach crest, indicate that it may be possible to preserve ghost crab populations on the beach while still permitting the use of ORVs. Closing the beach crest 24 hours a day may be the optimal solution for preservation of ghost crab populations. High-energy weather events, however, resulted in larger changes to the population dynamics of the ghost crabs. After storms, ghost crabs were able to (re)inhabit areas where their numbers previously had been reduced by the operation of ORVs. While temporary closures of the beach crest may be used to reduce the short-term impacts of ORVs on ghost crab populations on the outer banks of North Carolina, long-term impacts ultimately are controlled by the strength and frequency of storms that reset the system.

Characterization of wetland plant stress using leaf spectral reflectance: Implications for wetland remote sensing

Spectral measurements were recorded for leaves from two monospecific stands ofAcer rubrum in an attempt to characterize leaf reflectance at different stages of flooding. The stands occupied two different soil types possessing different soil moisture regimes. Leaves were excised from different parts of the trees, and their reflectance properties were measured with a hand-held spectroradiometer recording from 400 to 900 nanometers in 3-nm increments. Soil redox potentials were recorded at the sites in an attempt to characterize stress as a function of the soil reducing conditions. Spectral curves, reflectance peaks, soil moisture observations, and redox potentials were plotted and analyzed to document the conditions of the trees during a two-and-a-half month period in the early local growing season. Compared to non-flooded trees, spectral measurements for flooded trees showed elevated reflectance in both the green spectral region at 550 nm as well as the near infrared region at 770 nm. In addition, the reflectance measurements were strongly related (r >- 0.80) to redox potentials recorded during the same period. The results indicated that spectrally detectable changes in visible and near infrared leaf reflectance may be more influenced by prolonged flooding than saturation. This suggests that where remote sensing is used for wetland mapping, there may be optimal times to spectrally separate stands of forested wetlands during the growing season.

VEGETATION DYNAMICS IN RESPONSE TO ORGANIC MATTER LOADING RATES IN A CREATED FRESHWATER WETLAND IN SOUTHEASTERN VIRGINIA

Created wetlands are often limited in soil organic matter, a product that usually accumulates with long-term ecosystem succession. Although many studies have tested the effect of adding organic material to these systems, few have quantified the effect of various loadings of organic matter (OM) in created wetlands. The purpose of this study was to determine how vegetation composition, standing crop biomass, and woody vegetation development varied in a created freshwater wetland with respect to different loadings (0, 56, 112, 224, or 336 Mg ha−1) of a soil OM amendment. Soil C, N, and P were positively related to loading rate, as was soil surface elevation. Species richness, evenness, and diversity measurements, along with the Ellenberg Community Coefficient Similarity Index, suggested an overall similarity of plant assemblages regardless of loading rate. Standing crop biomass (580–790 g m−2) was not significantly correlated with OM loadings, but showed a significant curvilinear relationship with plot surface elevation. Woody vegetation development was correlated with OM loadings, plot elevation, and soil P, indicating a positive relationship with all three factors. An amendment loading of 112 Mg ha−1 provided the maximum benefit because it provided soil nutrient levels that were within the range of natural wetlands while also minimizing changes in soil surface elevation due to the added bulk material.

Primary Succession in a Created Freshwater Wetland

Abstract Plant cover, density, and standing crop biomass were measured and compared in a created wetland and an adjacent freshwater marsh (reference wetland) in Charles City County, Virginia. No significant difference was observed between monthly standing crop in the created wetland and the reference wetland. Species composition differed between sites (mean SI < 0.50) with no significant relationship between species composition and distance from adjacent seed source. Dominant species in the created wetland (Eleocharis obtusa, Juncus acuminatus) were dissimilar to those of the reference wetland (Dichanthelium dichotomum var. dichotomum, Scirpus cyperinus). Results suggest that if both standing crop and composition are going to be used to establish short-term goals for a created wetland, these two measures should not be considered interdependent. Further, the high relative importance of perennials within the created wetland does not fit primary succession predictions, indicating that certain wetland perennials utilize “annual” strategies when substrates are available. Management alternatives should accommodate establishment of these species, which are important in early successional development of created wetland sites.

Using a Floristic Quality Assessment Technique to Evaluate Plant Community Integrity of Forested Wetlands in Southeastern Virginia

Abstract Given the continuing degradation of freshwater wetland ecosystems throughout the Southeast, there has been significant interest in developing methods and indices to evaluate and monitor wetland biological integrity. The purpose of this study was to adapt and test the ability of a vegetation-based assessment technique known as Floristic Quality Assessment to detect the level of human impact in hardwood flat wetlands of Southeastern Virginia. We measured plant species diversity and composition within each vertical stratum [herbaceous, woody understory (shrub and sapling), and canopy] of 11 wetlands. We calculated a Floristic Quality Index (FQI) for each layer, and tested for relationship to land use disturbance patterns within defined site buffer and watershed areas. We found floristic quality of the herbaceous layer and the sapling portion of the woody understory layer to be negatively correlated with level of land use disturbance at both buffer and watershed scales, suggesting that FQI scores within these strata reflect current anthropogenic stress. While FQI of the canopy layer and the shrub portion of the woody understory layer were not reliable indicators of current land use disturbance, we found that a comparison of sapling and canopy layer FQIs gave insights into historic vs. recent floristic integrity of sites. Overall, our findings support the use of floristic quality assessments in evaluating wetland biological integrity when sampling and index calculation methodology are carefully adapted to local flora and community types.

York River Tidal Marshes

Abstract The York River has nine tidal wetland community types that are distributed along gradients of salinity and tidal inundation. These range from the Saltmarsh Cordgrass community dominated by Spartina alterniflora to the Tidal Freshwater Mixed community that can have over 50 species in one marsh. These tidal marshes provide a number of important functions and values to the estuarine systems including: high primary productivity, important habitat value, erosion buffering and filtering capacity useful for trapping sediments, pollutants and nutrients. The tidal marsh communities within the four Chesapeake Bay Virginia National Estuarine Research Reserve sites are situated along the York system in polyhaline, mesohaline, oligohaline and freshwater salinity regimes. They are largely pristine vegetation communities and have been documented to have abundant fauna characteristic of their individual community types. Changes in the vegetation communities of each site have been documented over time; however more research is needed on the potential effects of projected sea level rise on these habitats and the roles of watershed sedimentation and nutrient enrichment, vegetation succession, and invasive species on the persistence and value of these tidal marsh areas.

A Drawdown Flora in Virginia

Abstract Species composition and relative dominance (cover) were documented in an emergent macrophyte community on recently exposed sediment during an artificial drawdown of a large reservoir in the Coastal Plain of Virginia. Observations included nine county records (New Kent County), four of which were records for the Lower Peninsula of Virginia and are considered state rare species. Dominance calculations by distance class (five-meter increments from the original shoreline to the existing waterline) showed that certain species were locally dominant near the original shoreline (e.g., Fimbristylis autumnalis), whereas others, particularly the state rare species, were more prevalent near the drawdown waterline (e.g., Lipocarpha micrantha). These results suggest that the timing and magnitude of drawdown events may influence recruitment of the species observed in this study. These species appear to form seedbanks in the substrate of the reservoir for long periods of time, and are capable of rapid germination and regeneration (seed set) during short-lived, unpredictable drawdown conditions. Small seed size and other environmental factors accommodate a predisposition to this “temporal” niche. Based on this research and the work of others, we suggest that such species are part of a regional “drawdown flora.”

The Second Warning to Humanity – Providing a Context for Wetland Management and Policy

The Second Warning to Humanity provides a clarion call for wetland researchers and practitioners given the loss and degradation of wetlands, the declining availability of fresh water, and the likely consequences of climate change. A coordinated response and approach to policies has the potential to prevent further degradation and support resilient wetlands that can provide a range of ecosystem services, including buffering wetlands from climate impacts, and avoiding major climate amplification from temperature-induced release of additional carbon dioxide and methane while addressing the causes and consequences of global climate change. The Warning to Humanity also provides an opportunity for organisations such as the Society of Wetland Scientists to raise the profile of wetlands and to initiate a discussion on how to respond and change direction from the destructive development trajectory that led to wetland loss and degradation. It also provides a signal for a reappraisal of the effectiveness of the implementation of the Ramsar Convention on Wetlands as an international mechanism for ensuring the sustainability of wetlands.