Vegetation development in created, restored, and enhanced mitigation wetland banks of the United States

Wetlands (Impact Factor: 1.28). 25(1):51-63. DOI: 10.1672/0277-5212(2005)025[0051:VDICRA]2.0.CO;2

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Since wetland construction projects are becoming more commonplace, meaningful follow-up studies are needed to evaluate how these systems change over time. To that end, the objective of our study was to examine the temporal changes in plant community composition and water chemistry in two constructed wetlands. We investigated two wetland sites that were constructed in 2003 in northern Otsego County, NY, a county that is largely dominated by agriculture. Site 1 was previously an active cow pasture and site 2 was previously a wet meadow surrounded by agricultural fields. No active plant introduction was made during the construction; however, both sites were located in areas with many remnant wetlands and were connected to through-flowing streams. In 2004 (Year 1) and 2010 (Year 7), the plant community composition and nitrogen retention were assessed. We found that both sites experienced site-wide declines in plant species richness, including the loss of upland and facultative upland species and the unanticipated loss of facultative wetland and some obligate species. We propose that high water levels, which, at their maximum depth were >1.5 m deeper than in Year 1, maintained by landowners in the years after the initial survey, may have been responsible for the unexpected loss of wetland species. We also found that site 1 exhibited considerable nitrogen retention in both Year 1 and Year 7; however, N concentrations were low at site 2 in both years.
    Environmental Management 04/2013; · 1.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two parallel pilot-scale integrated vertical-flow constructed wetland systems (IVCWs) were employed to study the removal efficiencies for domestic wastewater and changes of microbial community structure during acclimation period. The results indicated that the acclimation period for common pollutants removal was 40 days. The mean removal rates during acclimation period were achieved for COD (77.02%), TN (57.21%), NH4+-N (45.63%) and TP (67.78%), respectively. Fatty acid methylesters (FAME) analysis and function groups PCA analysis demonstrated the microorganism community structure during the acclimation period realized stable after 90 days’ operation. Based on the results of purification effects and microbial community structure, 90 days was probably optimal acclimatization period for IVCW system under this experimental condition.
    Desalination and water treatment 11/2012; 48(1):302-309. · 0.85 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The United States has lost about half its wetland acreage since European settlement, and the effectiveness of current wetland mitigation policies is often questioned. In most states, federal wetland laws are overseen by the U.S. Army Corps of Engineers, but Michigan administers these laws through the state's Department of Environmental Quality (MDEQ). Our research provides insight into the effectiveness of the state's implementation of these laws. We examined wetland mitigation permit files issued in Michigan's Upper Peninsula between 2003 and 2006 to assess compliance with key MDEQ policies. Forty-six percent of files were out of compliance with monitoring report requirements, and forty-nine percent lacked required conservation easement documents. We also conducted site assessments of select compensatory wetland projects to determine compliance with MDEQ invasive plant species performance standards. Fifty-five percent were out of compliance. We found no relationship between invasive species noncompliance and past site monitoring, age of mitigation site, or proximity to roads. However, we found wetland restoration projects far more likely to be compliant with performance standards than wetland creation projects. We suggest policy changes and agency actions that could increase compliance with wetland restoration and mitigation goals.
    Environmental Management 04/2012; 50(1):97-105. · 1.65 Impact Factor