Reference Wetlands Research Articles

Floristic quality assessment for marshes in Alberta's northern prairie and boreal regions

Floristic quality indices are used to monitor and assess wetland condition by measuring a plant community's tolerance to environmental stress. The aim of our research was to evaluate whether stormwater and reclamation marshes supported wet meadow plant communities that were similar in floristic quality to reference wetlands. Coefficients of conservatism were assigned to a comprehensive list of marsh plant species by nine expert botanists. Various metrics such as the floristic quality index (FQI) were tested for a linear relationship to regional environmental stress gradients in 78 sites in the northern prairies (Aspen Parkland) and 66 sites in the Boreal Plains ecoregions in Alberta, Canada. Sensitivity of floristic quality metrics to the stress gradients was higher when rare species were excluded (species with <5% site-level cover). An adjusted FQI that eliminated bias towards sites with higher species richness yielded the strongest relationship to the stress gradient in both ecoregions (r2 = 0.55 in northern prairies; r2 = 0.46 in Boreal Plains). The adjusted FQI also yielded more consistent scores than richness-weighted metrics in a subset of 47 sites where sampling was replicated in dry and wet years (r = 0.75). Including exotic species in floristic quality metrics was not beneficial in the northern prairies where reference sites were located near areas of high urban and agricultural development. This study demonstrates that floristic quality assessments are reasonably good predictors of plant community condition in relation to environmental stress. Results of this study also highlight that existing stormwater ponds and reclamation marshes are not successfully restoring plant community habitat.

Immature mosquitoes in agricultural wetlands of the coastal plain of Georgia, U.S.A.: Effects of landscape and environmental habitat characteristics

This study is the first to report on the relationships between immature mosquitoes (larvae and pupae) and landscape and environmental habitat characteristics in wetlands associated with row crop agriculture. Indicator species analysis (ISA) was used to test for associations among mosquito species and groups of wetland sites with similar Landscape Development Intensity (LDI) values. Results indicated that Anopheles quadrimaculatus, Culex erraticus, and Psorophora columbiae were associated with agricultural wetlands (LDI>2.0), whereas Anopheles crucians and Culex territans were associated with forested reference wetlands (LDI<2.0) in both wet and dry years. The species fidelity to wetland type, regardless of the hydrologic regime, demonstrates these species are robust indicators of wetland condition. Data on immature mosquito assemblages were compared to selected landscape and environmental habitat variables using Akaike's Information Criterion (AICc) model selection. LDI indices, dissolved oxygen concentration, the proportion of emergent vegetation, and the proportion of bare ground in wetlands were important factors associated with the selected mosquito species. These results indicate that LDI indices are useful in predicting the distributions of disease vectors or other nuisance mosquito species across broad geographic areas. Additionally, these results suggest mosquitoes are valuable bioindicators of wetland condition that reflect land use and hydrologic variability.

Effects of sediment removal on vegetation communities in Rainwater Basin playa wetlands

Sedimentation from cultivated agricultural land use has altered the natural hydrologic regimes of depressional wetlands in the Great Plains. These alterations can negatively affect native wetland plant communities. Our objective was to determine if restored wetlands are developing plant communities similar to reference wetland conditions following hydrologic restoration. For this study, hydrology was restored via sediment removal. Thirty-four playa wetlands in reference, restored, and agricultural condition within the Rainwater Basin Region of Nebraska were sampled in 2008 and 2009. In 2008, reference and restored wetlands had higher species richness and more native, annual, and perennial species than agricultural wetlands. Restored wetlands had similar exotic species richness compared to reference and agricultural wetlands; however, reference wetlands contained more than agricultural wetlands. Restored wetlands proportion of exotics was 3.5 and 2 times less than agricultural wetlands and reference wetlands respectively. In 2009, reference and restored wetlands had higher species richness, more perennial species, and more native species than agricultural wetlands. Restored wetlands contained a greater number and proportion of annuals than reference and agricultural wetlands. Canonical Correspondence Analysis showed that reference, restored, and agricultural wetlands are dominated by different plant species and guilds. Restored wetland plant communities do not appear to be acting as intermediates between reference and agricultural wetland conditions or on a trajectory to reach reference conditions. This may be attributed to differing seed bank communities between reference and restored wetlands, dispersal limitations of perennial plant guilds associated with reference wetland conditions, and/or management activities may be preventing restored wetlands from reaching reference status.

HGM을 이용한 질날늪 기능평가 연구

Wetlands occupy an important ecological position on the earth, carrying out very important functions and roles both ecologically and hydrologically. However, due to past industrialization, not only wetland areas but also the biodiversity of organisms has severely decreased due to several artificial interferences and damage as wetlands began to be perceived simply as targets for development and reclamation. However in recent times, with the importance of wetlands coming to the fore, the assessment of the function and value of wetlands is being made for their wise use and systematic maintenance. Accordingly, this study targeted the Jilnal Wetlands located in Haman, Gyeongnam, and conducted a functional appraisal of this wetland using the modified HGM Model which was modified & developed appropriately for the actual conditions of our country. The result of its appraisal by selecting the Upo Wetland as the reference wetland, which is a criterion of the index, showed a comparatively positive functional index with 0.89 of the Upo Wetland average. This means that the Jilnal Wetland carrys out more than 89% of the functioning of the Upo Wetland. In this regard, it is thought that the Jilnal Wetland could carry out the wetland functioning equivalent to that of the Upo Wetland through a little more systematic management.

Impacts of Fire on Microbial Carbon Cycling in Subtropical Wetlands

Fire is a major determinant of the global carbon (C) balance. While it is known that C is lost through organic matter combustion, the effect fire has on soil C biogeochemistry is unclear. Studies investigating the role of fire on C greenhouse gas production (CO2 and CH4) have been conducted in forested and grassland ecosystems, yet research in wetlands has been limited. With their high potential for C storage, wetland ecosystems are important in C cycling while simultaneously serving as the largest single CH4 source in the world. Wildfires typically consume a majority of the above-water biomass in wetland systems that result in direct C losses, but the subsequent implications for C processing are unknown. Thus, understanding C cycling in wetlands regularly maintained or influenced by fire is critical to meeting C sequestration management objectives. This study focused on a fire-adapted wetland ecosystem undergoing restoration from agricultural impacts within the Everglades National Park, Florida, USA. Within the site, the effects of prescribed fire on C cycling (organic C, extractable organic C, enzyme activity, CO2, and CH4 production) were monitored in a restored (high-phosphorus [P]) and reference (low-P) wetland at both high and low elevations. Because fire can affect both C and P forms and availability, the objective of this study was to investigate the short- (two-day) and long-term (one-year) effect of fire on C cycling in subtropical wetlands soils of varying soil nutrient concentrations. Initially (two days post fire), C cycling was stimulated in both soils. However, stimulation of CO2 and CH4 production was observed only at the reference (low-P) site. This result suggests that fire may have an adverse effect on C cycling in low-P soils, initially augmenting C greenhouse gas production. Minimal heat transfer coupled with constant microbial biomass suggests that nutrients may have been a regulating factor in this process. After one year, no fire effect was distinguishable on C parameters from reference sites, yet variable effects were observed in restored soils. This suggests that C cycling in reference sites may recover more quickly than restored sites. The ultimate consequences of fire on C cycling in these wetlands systems are dependent on time and are strongly influenced by pre-fire site conditions.

Seed bank responses to wetland restoration: Do restored wetlands resemble reference conditions following sediment removal?

Sedimentation and alterations of natural hydroperiods from watershed cultivation have affected most depressional wetlands in the Great Plains. This can result in altered plant community structure through changes in water availability and depth as well as burial of seed banks. The vegetation and seed banks of 15 wetlands were sampled within the Rainwater Basin Region of Nebraska. Our objectives were to: (1) compare wetland seed bank communities among wetlands with different watershed land uses (reference, restored and impacted by watershed cultivation); (2) determine the available seed bank following sediment removal and establish if wetland zonation occurs in the deeper sediment layer of pre-scraped agricultural wetlands; and (3) determine the similarity between extant vegetation and the seed banks for each wetland land use treatment. There were no significant differences in seed bank species richness and the number and composition of annual, perennial, native, or exotic species among reference, restored, and agricultural playas. Restored wetlands had a greater number of upland species germinate from the surface soil seed bank compared to reference and agricultural playas. Availability of seeds after 30cm of soil was removed (to simulate available seed bank if the wetland was to be restored) in crop land use wetlands was low (2–52 seeds/wetland) making determination of wetland zonation difficult. There was no difference in the similarity between the seed bank and extant vegetation among the three land use treatments. Sediment removal appears to be successful in removing weedy and exotic species from the seed bank; however, the seed bank is not the primary source for playa wetland revegetation. Restored and reference wetlands have similar seed bank community characteristics (i.e., richness) however, each wetland land use treatment was associated with differing plant species and plant guilds.

Predicting dispersal-limitation in plants: Optimizing planting decisions for isolated wetland restoration in agricultural landscapes

Isolated wetlands are often degraded by agriculture, increasing sediment accretion and altering plant composition. Two common opposing wetland restoration practices are self-design vs. intensive revegetation. Self-design restores hydrogeomorphology without inoculating wetland taxa into restoration sites. Self-design may not meet restoration targets if dispersal-limited plants do not colonize restoration sites. Alternatively, intensive revegetation (hydrogeomorphic restoration combined with revegetation) is costly and time consuming. We investigated plant dispersal-limitation in 309 isolated wetlands among two agricultural landscapes in the U.S. Great Plains (the western High Plains (WHP) and the Rainwater Basin (RWB)) and three land-uses (reference, croplands, and previous croplands) to predict optimal restoration practices. We present analytical tools predicting whether self-design or intensive revegetation will be more successful elsewhere. In the WHP and RWB, perennial wetland cover was 61% and 31% greater in reference than in other land-uses. Distance to the nearest reference wetland explained perennial wetland richness in both regions, and area of reference wetlands within 15km also was important in the WHP. Annual wetland species were over-represented in previous cropland wetlands and were less influenced by landscape isolation. We analytically identified dispersal-limited and cosmopolitan species in reference wetlands, with distance to reference wetlands and area of surrounding reference wetlands important in determining composition. Further, dispersal-limited plants in reference wetlands had greater cover in clustered than isolated wetlands in previous croplands. Plant community patterns in reference conditions may predict composition in restored wetlands. This aids selection of self-design or revegetation restoration approaches for individual plant species in isolated wetlands.

Ecosystem Development After Mangrove Wetland Creation: Plant–Soil Change Across a 20-Year Chronosequence

Mangrove wetland restoration and creation efforts are increasingly proposed as mechanisms to compensate for mangrove wetland losses. However, ecosystem development and functional equivalence in restored and created mangrove wetlands are poorly understood. We compared a 20-year chronosequence of created tidal wetland sites in Tampa Bay, Florida (USA) to natural reference mangrove wetlands. Across the chronosequence, our sites represent the succession from salt marsh to mangrove forest communities. Our results identify important soil and plant structural differences between the created and natural reference wetland sites; however, they also depict a positive developmental trajectory for the created wetland sites that reflects tightly coupled plant-soil development. Because upland soils and/or dredge spoils were used to create the new mangrove habitats, the soils at younger created sites and at lower depths (10–30 cm) had higher bulk densities, higher sand content, lower soil organic matter (SOM), lower total carbon (TC), and lower total nitrogen (TN) than did natural reference wetland soils. However, in the upper soil layer (0–10 cm), SOM, TC, and TN increased with created wetland site age simultaneously with mangrove forest growth. The rate of created wetland soil C accumulation was comparable to literature values for natural mangrove wetlands. Notably, the time to equivalence for the upper soil layer of created mangrove wetlands appears to be faster than for many other wetland ecosystem types. Collectively, our findings characterize the rate and trajectory of above- and below-ground changes associated with ecosystem development in created mangrove wetlands; this is valuable information for environmental managers planning to sustain existing mangrove wetlands or mitigate for mangrove wetland losses.

Using Vegetative Nutrient Stocks to Compare Restored and Reference Wetlands in the Upper Klamath Basin, Oregon

Vegetative diversity metrics are often used to characterize wetland restoration success. Here we examine whether other important vegetative traits (nutrient standing stocks and tissue nutrient concentrations) can improve our understanding of the structure of restored and reference wetlands and aid in the assessment of functional equivalency. We focus on wetlands of the Upper Klamath Basin (UKB), Oregon because this basin supports a mosaic of remnant, restored, and degraded wetlands dominated by a limited number of common emergent plant species. We summarize nutrient standing stocks using 11 growth limiting micro- and macronutrients present in aboveground tissues of three emergent plant species. We show that interspecific variation in nutrient standing stocks and tissue nutrient concentrations was high and greater than inter-site differences. Interspecific variation for nitrogen standing stocks was 3X larger than inter-site variation. Although less common, inter-site differences in nutrient standing stocks and tissue nutrient concentrations were detected and tissue phosphorus concentrations in a recently restored wetland were nearly twice those of a reference wetland; corresponding levels of aboveground biomass in this wetland were not detected. Our detection of elevated phosphorus in the vegetation of a recently restored wetland is consistent with predictions from both experimental and observational work in UKB and demonstrates that nutrient standing stocks provide important clues about the fate and retention of nutrients in restoration wetlands. Importantly, we show that these vegetative attributes also provide a measure of functional equivalency that is rarely used in the assessment of restoration success.

Community congruence of plants, invertebrates and birds in natural and constructed shallow open-water wetlands: Do we need to monitor multiple assemblages?

Biomonitoring is a common means of evaluating wetlands. It is based on the premise that the community composition of one taxonomic group is indicative of overall biology and the underlying environmental conditions at a wetland. To be a good bioindicator, there must be adequate concordance between the indicator group and other biotic assemblages. Otherwise, multi-assemblage monitoring is necessary to glean a complete picture of wetland condition. In 32 sites ranging from reference wetlands to stormwater retention ponds, we evaluated concordance in community composition among the six most commonly monitored wetland assemblages: waterfowl, wetland dependent songbirds, aquatic macroinvertebrates, and plants in the wet meadow, emergent, and open-water vegetation zones. We also assessed agreement in environmental correlates among these six assemblages and investigated the impact of human disturbance on cross-assemblage concordance. We found that cross-assemblage concordance was positive (p<0.03 in 14 of 15 pair-wise comparisons, p=0.06 in 15th case), but relatively low (Mantel R values 0.11–0.37), suggesting that the assemblages are mediocre surrogates for one another. Yet, we found very strong agreement among environmental correlates of the six assemblages, especially along the first axis of assemblage-specific ordinations (mean Spearman rho=0.923), indicating that despite low concordance, the six assemblages are likely responding to the same environmental gradients. Thus, while a single assemblage may not serve as a surrogate for the other assemblages, it should yield an adequate estimate of underlying environmental conditions and the degree of disturbance. Most important among the environmental correlates were sediment and water nutrient levels, shoreline slope, and the size of wet meadow and emergent vegetation zones. Perhaps most interestingly, we found that the strength of cross-assemblage concordance was greatest in reference wetlands and was lower (p≤0.05) in constructed wetlands. This implies that cross-assemblage concordance present in undisturbed sites may not persist in disturbed wetlands where several of these cross-assemblage relationships deteriorate. Furthermore, a general change in cross-assemblage concordance may itself be indicative of human disturbance in wetlands.

Environmental Reviews and Case Studies: Restoring a Salt Marsh in a Highly Urbanized Environment of New York City: The Alley Park Restoration Project

The success of urban salt marsh restoration depends upon an understanding of the local tidal regime and hydrologic conditions. Reference wetland characteristics can provide biological and physical restoration baselines for a restoration design through the use of techniques such as bio-benchmarking and geomorphologic assessment. Reference site vegetation can be used as indirect indicators of local tidal elevations and duration of flooding of each tidal zone. Reference sites can also provide landscape allometry to generate geomorphologic ratios that can be applied to the restoration site. Through the use of field measurements, aerial photographs, and GIS technology, relationships can be identified for tidal channel width, depth, diurnal tidal prism, and marsh area. Calculating a hydrologic budget for freshwater is critical to estimate salinity concentrations and their effect on the restoration wetland. This information, along with field measurements of salinity, can be used to predict salinity ranges result...

Creating Wetlands: Primary Succession, Water Quality Changes, and Self-Design over 15 Years

The succession of vegetation, soil development, water quality changes, and carbon and nitrogen dynamics are summarized in this article for a pair of 1-hectare flow-through-created riverine wetlands for their first 15 years. Wetland plant richness increased from 13 originally planted species to 116 species overall after 15 years, with most of the increase occurring in the first 5 years. The planted wetland had a higher plant community diversity index for 15 years, whereas the unplanted wetland was more productive. Wetland soils turned hydric within a few years; soil organic carbon doubled in 10 years and almost tripled in 15 years. Nutrient removal was similar in the two wetlands in most years, with a trend of decreased removal over 15 years for phosphorus. Denitrification accounted for a small percentage of the nitrogen reduction in the wetlands. The wetlands were effective carbon sinks with retention rates of 1800–2700 kilograms of carbon per hectare per year, higher than in comparable reference wetlands and more commonly studied boreal peatlands. Methane emission rates are low enough to create little concern that the wetlands are net sources of climate change radiative forcing. Planting appears to have influenced carbon accumulation, methane emissions, and macrophyte community diversity.

Dominance of native grasses leads to community convergence in wetland restoration

Wetland restoration is a pressing conservation priority, but there are few replicated field studies that provide a scientific foundation for these activities. We conducted a 3-year, replicated field experiment to examine the effectiveness of initial site preparation techniques (combinations of solarization, herbicide, tilling, and thermal weed control) in restoring native plant biodiversity to an agricultural field in a former wetland prairie in Oregon, USA. Post-treatment, plots were sown with a typical restoration mix of native graminoids and forbs. Treatments were compared to three high-quality managed reference wetlands and the adjacent agricultural field. Site preparation treatments varied in their effectiveness in suppressing extant vegetation and eliminating the residual seed bank. After 1 year, the solarization and fall herbicide application treatments were the most effective at reducing exotic cover. However, after 3 years, plant community composition converged in all treatments due to a loss of annual species and increasing dominance of native perennial bunchgrasses. Plant community composition became more similar to the reference wetlands each year, but diversity and richness diverged, apparently due to a trade-off between the cover of the dominant native bunchgrasses and diversity. Successional theory offers insights into how priority effects and competitive inhibition may influence community trajectories, and offers a useful model for restoring plant communities with high native diversity and dominance. Finding ways to mitigate the tradeoff between native plant cover and diversity by actively managing successional trajectories is an important challenge in wetland restoration that deserves further investigation.

Hydrogeomorphic (HGM) Assessments of Mitigation Sites Compared to Natural Reference Wetlands in Pennsylvania

The U.S. Environmental Protection Agency and U.S. Army Corps of Engineers completed revisions to the Mitigation Rule of the Clean Water Act in 2008. These revisions encourage states to carry out mitigation in a watershed context, prioritizing mitigation site design and placement by overall watershed need, to the extent appropriate and practicable (33 C.F.R. 332.3(c)). States are expected to establish monitoring programs and measureable performance standards for mitigation wetlands. In Pennsylvania, hydrogeomorphic (HGM)-based assessments involving 222 reference wetlands were used to compare mitigation wetland performance. For this study, 72 mitigation wetlands were sampled in 2007 and 2008 from three categories – Pennsylvania Wetland Replacement Program sites, Pennsylvania Department of Transportation mitigation banks, and permit required compensatory mitigation sites. Mitigation wetlands were intensively sampled using a Level 3 - Intensive methodology developed by Riparia. Field data and GIS computed variables were used to derive the scores of 10 HGM functional capacities. Overall, mitigation sites displayed lower potential to perform a characteristic wetland function than reference wetlands. Depressions show the greatest discrepancy, while fringing sites showed the least amount of difference from reference scores. Mitigation site size, age, and type were not significant factors in functional capacity index scores.

Plant Community Composition and Waterfowl Food Production on Wetland Reserve Program Easements Compared to Those on Managed Public Lands in Western Oregon and Washington

The Wetland Reserve Program (WRP) is one conservation tool used to mitigate national wetland loss, but few studies have evaluated the WRP for wildlife. During falls 2008 and 2009, we evaluated wetland plant communities and seed densities on 23 WRP wetlands in relation to 23 reference wetlands on managed public lands in the Willamette Valley and Lower Columbia River Valley (LCRV) of western Oregon and southwest Washington. Plant community on WRP easements differed by management intensity (A = 0.111, p = 0.002) with perennial and introduced species indicative of unmanaged easements and annuals indicative of actively managed wetlands, but plant community composition did not differ between WRP and reference wetlands (A = 0.003, p = 0.21). Overall, seed biomass was similar between WRP and reference wetlands (F1, 41 = 2.44, p = 0.12), but this relationship varied by study region (F1, 41 = 12.6, p = 0.001) related to management intensity. Seed biomass was greater on actively (765 ± 105 kg/ha) vs. passively (349 ± 105 kg/ha) managed sites (F3, 34 = 9.90, p = 0.003). Seasonal wetlands on WRP easements can achieve a structure and function similar to reference sites. However, we suspect that in the absence of active management the value of WRP sites will decline as the plant community shifts to being dominated by introduced perennial species like reed-canary grass that will reduce the diversity of native wetland plants and lower seed abundance for waterbirds.

A Place to Call Home: Amphibian Use of Created and Restored Wetlands

Loss and degradation of wetland habitats are major contributing factors to the global decline of amphibians. Creation and restoration of wetlands could be a valuable tool for increasing local amphibian species richness and abundance. We synthesized the peer-reviewed literature addressing amphibian use of created and restored wetlands, focusing on aquatic habitat, upland habitat, and wetland connectivity and configuration. Amphibian species richness or abundance at created and restored wetlands was either similar to or greater than reference wetlands in 89% of studies. Use of created and restored wetlands by individual species was driven by aquatic and terrestrial habitat preferences, as well as ability to disperse from source wetlands. We conclude that creating and restoring wetlands can be valuable tools for amphibian conservation. However, the ecological needs and preferences of target species must be considered to maximize the potential for successful colonization and long-term persistence.

Man-made Mediterranean temporary ponds as a tool for amphibian conservation

Mediterranean temporary ponds (MTPs) are crucial breeding sites for local amphibians, a faunal group in decline in the Mediterranean mainly due to wetland destruction. Although the disappearance of len- tic habitats in other regions of the world has been ameliorated by the creation and restoration of wetlands, these tactics remain untested in Mediterranean wetlands. To evaluate the amphibian colonization dynamics of artificial MTPs in the north-eastern Iberian Peninsula, we monitored two artificial MTPs (one in a high- diversity area and the other in a low-diversity area) over 2 years. We selected reference wetlands at each area, and amphibian communities of man-made MTPs were compared to those of reference wetlands. We found that, beginning in the first year, artificial MTPs were a valuable habitat for regional amphibian fauna. Posteriorly, we focused on the reproductive success of the natterjack toad, Bufo calamita. Using a drift fence equipped with pit-fall traps, we measured the abundance of both reproductive adults entering the pond and post-metamorphic individuals exiting the pond. Using mark-recapture methods, we analyzed the time and energy costs associated with reproduction in the artificial MTPs. We observed a highly variable colonization dynamics between sites, between hydroperiods, and within hydroperiods, and these dynamics often depended on meteorological factors. Our results suggest that even at a short timescale, native amphibian species such as B. calamita can benefit from wetland creation in the Mediterranean region.

Heavy metals (Cr and Ni) distribution and fractionation in cropland soils from reclaimed tidal wetlands in Pearl River estuary, South China

Abstract Heavy metal contamination was compared for soils with different land use (cropland and wetland) in the reclaimed region of the Pearl River estuary. A sequential extraction technique was used to produce five chemical fractions (exchangeable (F1), carbonate (F2), Fe–Mn hydroxide (reducible) (F3), organic (F4) and residual (F5)) to study the effects of reclamation and tillage on the distribution and mobility of the heavy metals Cr and Ni. The results revealed that generally the contamination levels increased with a longer history of reclamation (100> 40> 30> 10 years) whilst an undisturbed reference wetland was least affected. The most substantial quantities of both Cr and Ni were observed in the residual fraction, which may be a consequence of the mixing effects of soil tillage and planting. With the exception of the 20-30 cm layers from the wetland and 10 year old cropland samples, the total concentration of Cr and Ni at all sites and all soil layers exceeded the moderately polluted level according to the SQGs of the US EPA.

Structural and functional vegetation development in created and restored wetland mitigation banks of different ages

Vegetation surveys of seven Ohio wetland sites were conducted from 2008 to 2010 during peak biomass. These seven sites included five created/restored mitigation bank wetlands, a created riverine research wetland, and a natural reference wetland. All of the created/restored wetlands ranged in age from 3 to 18 years. The objective of this study was to examine the development of vegetation structure and function of mitigation bank wetlands less then 20 years of age and to compare these to reference wetlands. Vegetation structure examined included species richness, floristic quality assessment index (FQAI), Shannon–Wiener diversity index ( H), and community diversity index (CDI). Functional attributes included aboveground net primary productivity (ANPP) and functional group composition of dominant species. For both structure and function, the reference wetlands were statistically different from the wetland mitigation bank sites ( P < 0.001, MANOVA). Structurally, there were significant differences of FQAI score ( P < 0.05) and species richness ( P < 0.05) with age in the mitigation sites. Functionally, there was a significant difference between ANPP ( P < 0.05) and age in the mitigation sites. Over the different types of wetlands, the reference wetlands had significantly different ANPP, FQAI scores, and species richness than did the mitigation sites ( P < 0.001, P < 0.05, and P < 0.001, respectively). CDI and H were not statistically different between mitigation sites and the reference wetlands. ANPP, FQAI, and species richness tended to be higher in the reference sites than in the mitigation sites. Overall, the mitigation bank wetlands were not statistically similar to the reference sites. Within the mitigation banks, the younger sites had higher values for structural attributes than the older mitigation sites.

Biological Nitrogen Fixation in Periphyton of Native and Restored Everglades Marl Prairies

Periphyton mats are an important component of the Everglades ecosystem. These mats are able to fix atmospheric nitrogen; however little attention has been paid to this function throughout much of the Everglades system. The objective of this study was to characterize and quantify periphyton N2 fixation in the Hole-in-the-Donut (HID) region of the southern Everglades, where farmed marl prairie wetlands have been restored through complete soil removal to reduce nutrient levels. Significantly higher N2 fixation rates (measured acetylene reduction) were found in periphyton of the areas cleared in 2000 and 2003 (3–10 nmol g−1 DW h−1) compared to the reference wetland site (less than 1 nmol g−1 DW h−1). Overall rates were stimulated by light (~2 times the measured dark rates). Areal estimates of fixed N were low compared to other Everglades, ranging from 0.1–0.2 g N m−2 yr−1 in the restored sites to 0.05 g N m−2 yr−1 in the reference area. Stable N isotopic ratios (i.e., δ15 N) ranged from −1.0‰ to 0.2‰ and were correlated with nitrogenase activity and TN:TP ratios. These findings suggest that periphyton nitrogenase activity and δ15 N could serve as indicators of nutrient status and restoration success in these systems.