Wetland mitigation banking is the practice of creating, restoring, enhancing, or preserving large, off-site wetlands to compensate
for authorized impacts to natural wetlands. By 2002, there were 219 active mitigation banks in the United States, encompassing
50,000 hectares in 29 states. This study is the first systematic analysis of the ecological quality of these ecosystems; the
objective is to determine if mitigation banks are successfully supporting native wetland vegetation and if success differs
by mitigation method (created, restored, or enhanced), geomorphic class, age, or area. I obtained monitoring reports from
45 randomly selected mitigation bank wetlands in 21 states to evaluate three measures of ecological status: the prevalence
of wetland vegetation, the pervasiveness of non-native species, and plant species richness. Sites range from less than one
ha to over 560 ha and include 17 created wetlands, 19 restored wetlands, and 9 enhanced wetlands. Prevalence Index scores
(PI; 1.0 for obligate wetland vegetation to 5.0 for upland vegetation) do not differ by wetland area but are significantly
lower in created wetlands and significantly decrease from one- and two-year-old created wetlands (PI=2.37±0.15; mean±SE) to
those five to seven years old (PI=1.96±0.12). Created and restored wetlands support 12.4 and 12.2 species per 10 m2 respectively, nearly four times more than the 3.2 species in 10m2 of enhanced wetland. This is in part attributable to a greater incidence of non-native species in created and restored wetlands.
The vegetative cover in created mitigation bank wetlands is 18.9±2.8 percent non-native-statistically similar to that of restored
(17.6±2.9) but significantly greater than that of enhanced systems (8.7±2.7). Within mitigation methods, there are clear differences
among geomorphic and vegetation classes. Depressional systems with a single vegetation class support highly hydrophytic, highly
non-native communities with low species richness, while restored and enhanced riverine systems have a greater prevalence of
native species. For mitigation bank wetlands in this study, the prevalence of wetland vegetation, the representation of native
species, and the plant community homogeneity increase with age, indicating a period of self-organization and a potential trend
toward vegetative equivalence with natural wetlands.
"However when ecosystems have been entirely destroyed, questions arise, such as (1) how to define a reference site in this case and (2) how to find the appropriate strategy for estimating restoration success. Various authors suggest that restoration success could be based on the survey of one ecosystem component such as vegetation structure (Matthews et al., 2009; Spieles, 2005; Stefanik and Mitsch, 2012), hydrological characteristics (Hohensinner et al., 2007) or macro-invertebrate communities (Spieles et al., 2006), while others promote a more integrated approach including many variables in order to provide a better assessment of restoration success (Andersen et al., 2006; Hobbs and Norton, 1996; Passoni et al., 2009). Nevertheless, few authors have attempted to use soil functioning as an indicator of wetland restoration success, although soils perform multiple ecological functions such as being a carbon sink and a nitrogen removal (Mitsch and Gosselink, 2000). "
[Show abstract][Hide abstract] ABSTRACT: The creation and restoration of new wetlands to mitigate wetland losses is a newly developing sciencewhose success still needs to be assessed. This study focuses on the ecological restoration of a gravel-pit in the low valley of the Seine estuary (France). Restoration consisted in filling the gravel-pit usinga hydraulic technique with dredged sediments from the Seine river and covering it with alkaline peatfrom adjacent wet meadows. Our objectives were to survey the functions of recreated soil 3 years afterthe gravel-pit was filled and assess whether it regained typical wetland functionality and to determinewhich soil functioning parameters are the most efficient for assessing restoration success. To addressthese questions, an approach combining analyses of in situ and ex situ soil functioning was used. Thesurvey was conducted on recreated soil as compared to a control soil (i.e. soil before gravel extraction).Four topographic zones were sampled corresponding to 4 types of recreated soil functioning in terms ofwaterlogging conditions: Hemic Histosol without waterlogged periods, Hemic Histosol with temporarywaterlogged periods, Hemic Histosol with the longest waterlogged periods and Interstratified Histosolwithout waterlogged periods. Soil respiration and SIR results showed that large stocks of organic matterare maintained after 3 years of restoration and proved able to sequester C in recreated soils. 3 yearsafter restoration, nitrogen removal function measured through denitrification technique was restored inthe Hemic Histosol with the longest waterlogged periods. These results demonstrate that waterloggingregime maintain the C stock and accelerate the restoration of denitrification process.
"The spread of urbanization and industrialization has escalated wetland degradation in many parts of the world, in both developing and developed countries (Tiner, 1984; Holland et al., 1995; Dahl, 2000; Ralph, 2003; Zedler and Kercher, 2005). Previous studies of wetland protection focused mainly on the functioning of constructed wetlands, ecological water demands and vegetation development (Spieles, 2005; Chen et al., 2009; Cui et al., 2009). For different kinds of wetlands, changing environmental flow is an important risk factor that needs to be considered when undertaking ecological restoration and management of water resources of basins (Yang and Mao, 2011). "
[Show abstract][Hide abstract] ABSTRACT: Nowadays, wetlands are at risk from a wide range of stress factors. Practical application of wetland ecological risk assessment will result in a better understanding of how physical, chemical, and biological stressors impinge on wetlands and will provide a framework for prudent wetland management. An important aspect of wetland management is to identify ecological risks affecting the area and to develop a wetland-zoning map based on those risks. This study uses a process of ecological risk assessment (ERA) to identify stress factors and responses within the framework of an ecosystem-based approach. All potential environmental factors, physical, chemical and biological need to be examined in context. This study aims to present a systematic methodology for risk assessment and zoning of wetland ecosystems. Initially, the most important risks threatening wetlands are identified in an ecosystem-based approach. Endpoint assessments are defined according to values and functions of the wetland and the ecological risks associated with these endpoints are identified. In the characteristics step, risks are analyzed according to severity, probability and a range of consequences. A Multi Criteria Decision Making (MCDM) method is used to prioritize these risks on the basis of experts' opinions. Geographic Information System (GIS) is used to develop a zoning map with a combination of risk layers according to importance. Finally, management strategies are proposed to deal with the risks. The proposed methodology was applied to Shadegan International Wetland, located in southwestern Iran. This wetland is in the Montero list and is currently threatened by various risks. According to the results, high-ranking potential risks and areas with different levels of risk and management strategies were proposed for this wetland.
"Soil development is closely related to vegetation development that is often the single attribute used to evaluate the success of wetland mitigation (Spieles, 2005). Soil physicochemical attributes, including bulk density, moisture, soil organic matter (SOM), total organic carbon (TOC), and texture are all inevitably linked to the development of plant communities in wetlands (Ballantine and Schneider, 2009; Ehrenfeld et al., 2005) and often heavily impacted by construction processes used in wetland construction (Whittecar and Daniels, 1999; Stolt et al., 2000; Science of the Total Environment 443 (2013) 725–732 ⁎ Corresponding author. "
[Show abstract][Hide abstract] ABSTRACT: We used multi-tag pyrosequencing of 16S ribosomal DNA to characterize bacterial communities of wetland soils collected from created and natural wetlands located in the Virginia piedmont. Soils were also evaluated for their physicochemical properties [i.e., percent moisture, pH, soil organic matter (SOM), total organic carbon (TOC), total nitrogen (TN), and C:N ratio]. Soil moisture varied from 15% up to 55% among the wetlands. Soil pH ranged between 4.2 and 5.8, showing the typical characteristic of acidic soils in the Piedmont region. Soil organic matter contents ranged from 3% up to 6%. Soil bacterial community structures and their differences between the wetlands were distinguished by pyrosequencing. Soil bacterial communities in the created wetlands were less dissimilar to each other than to those of either natural wetland, with little difference in diversity (Shannon's H') between created and natural wetlands, except one natural wetland consistently showing a lower H'. The greatest difference of bacterial community structure was observed between the two natural wetlands (R=0.937, p<0.05), suggesting these two natural wetlands were actually quite different reflecting differences in their soil physicochemistry. The major phylogenic groups of all soils included Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatinomadetes, Nitrospira, and Proteobacteria with Proteobacteria being the majority of the community composition. Acidobacteria group was more abundant in natural wetlands than in created wetlands. We found a significant association between bacterial community structures and physicochemical properties of soils such as C:N ratio (ρ=0.43, p<0.01) and pH (ρ=0.39, p<0.01). The outcomes of the study show that the development of ecological functions, mostly mediated by microbial communities, is connected with the development of soil properties in created wetlands. Soil properties should be carefully monitored to examine the progress of functional wetland mitigation.
Science of The Total Environment 12/2012; 443C:725-732. DOI:10.1016/j.scitotenv.2012.11.052 · 4.10 Impact Factor
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