Reference Wetlands Research Articles

Quantifying a stress gradient: An objective approach to variable selection, standardization and weighting in ecosystem assessment

Abstract Quantifying relative habitat quality is an important means of ecosystem assessment, and an essential step in the development and validation of indices of biotic integrity (IBI). Variables included in multi-metric IBIs are selected on the basis of their correlation with a human disturbance gradient, and the IBI is tested by examining correlation between IBI scores and rankings on the human disturbance gradient for an independent suite of sites. We present an objective approach to develop a disturbance gradient that ranks sites based on local-level measurements of physical and chemical stress; however, it could equally be applied to GIS-derived data. We measured 52 variables at three types of wetland in Alberta: reference wetlands, oil sands reclamation wetlands exposed to mine tailings, and reclamation wetlands free from tailings contamination. We used the data's correlation structure to select a sub-set of variables that minimized redundancy while retaining sensitivity and interpretability. The optimal sub-set included eight variables: chloride, cation and nitrogen content of water; water and oil content of sediment; water depth and amplitude and Secchi depth/total depth. We combined these eight environmental variables using different combinations of standardization (conversion to a common unit) and weighting schemes to produce six multi-metric stress indices. We evaluated the stress indices on their ability to discriminate among our three wetland types. The indices differed in their sensitivity to stress. Standardization had greater influence on index score than weighting. While all stress indices detected a difference among the three wetland types, only two were able to discriminate between the two classes of reclamation wetlands, both of which used percentile binning to standardize variables. The optimal stress index was standardized by percentile binning and weighted such that water quality, sediment chemistry, physical structure, and the level of tailings contamination were weighted equally. The approach we developed is repeatable and produced a sensitive index of wetland condition that is easily interpreted and relies minimally on best professional judgment. It may be suitable for measuring restoration success or the impact of any anthropogenic disturbance in a variety of ecosystem types.

Microbial Community Structure and Denitrification in a Wetland Mitigation Bank

Wetland mitigation is implemented to replace ecosystem functions provided by wetlands; however, restoration efforts frequently fail to establish equivalent levels of ecosystem services. Delivery of microbially mediated ecosystem functions, such as denitrification, is influenced by both the structure and activity of the microbial community. The objective of this study was to compare the relationship between soil and vegetation factors and microbial community structure and function in restored and reference wetlands within a mitigation bank. Microbial community composition was assessed using terminal restriction fragment length polymorphism targeting the 16S rRNA gene (total bacteria) and the nosZ gene (denitrifiers). Comparisons of microbial function were based on potential denitrification rates. Bacterial community structures differed significantly between restored and reference wetlands; denitrifier community assemblages were similar among reference sites but highly variable among restored sites throughout the mitigation bank. Potential denitrification was highest in the reference wetland sites. These data demonstrate that wetland restoration efforts in this mitigation bank have not successfully restored denitrification and that differences in potential denitrification rates may be due to distinct microbial assemblages observed in restored and reference (natural) wetlands. Further, we have identified gradients in soil moisture and soil fertility that were associated with differences in microbial community structure. Microbial function was influenced by bacterial community composition and soil fertility. Identifying soil factors that are primary ecological drivers of soil bacterial communities, especially denitrifying populations, can potentially aid the development of predictive models for restoration of biogeochemical transformations and enhance the success of wetland restoration efforts.

Ecosystem Characteristics and Summer Secondary Production in Stormwater Ponds and Reference Wetlands

Stormwater ponds (SWPs) are wetlands created or engineered for the purpose of collecting and controlling urban runoff, sediments, and toxins prior to discharging into other surface and/or ground waters. As wetlands face increasing pressure from development, many SWPs are also considered by planners as a valid solution to the problem of wetland habitat loss. This study compares water chemistry, organic matter dynamics, and macroinvertebrate community structure, biomass, and secondary productivity in a sample of SWPs with nearby reference wetlands of natural origin. Although total secondary productivity of invertebrates was greater in SWPs, significant differences were observed in water chemistry, invertebrate community structure, invertebrate biomass turnover, and organic matter dynamics that suggest that the SWPs were not comparable to the reference wetlands from the point of view of ecosystem function and conservation. Furthermore, improvement in the function of SWPs in pollutant control might be achieved by improving their function in conservation, most notably by considering the role of organic matter inputs from adjacent terrestrial areas in the planning.

Metals evaluation in coastal wetlands receiving treated wastewater

PurposeThe purpose of this paper is to describe the investigation of distribution of metals in water and sediment samples of Poydras‐Verret wetland, an area that has received approximately 40 years input of secondarily treated municipal effluent.Design/methodology/approachWater and sediment samples were analyzed for metals for a period of 18 months. These metals were also monitored for the secondarily treated effluent, and at a reference/control wetland that does not receive wastewater. Analysis of variance (ANOVA) and Student Newman‐Keuls post‐hoc ANOVA analysis were conducted to evaluate the pattern of metal distribution within the Poygras‐Verret wetland and compare results to the reference wetland. Heavy metal criteria established by United States Environmental Protection Agency (USEPA) and State of Louisiana were also used to assess the potential chronic and acute health impacts of heavy metals in the Poydras‐Verret wetland.FindingsConcentrations of metals of the Poydras‐Verret wetland water are not different from those found in the reference wetland water, suggesting no observed accumulation of these metals within the receiving wetland water. All metals are below the acute criteria.Originality/valueHistorical data regarding metal accumulation in wetlands in the published literature is limited. This paper provides supporting evidence that using wetlands to assimilate wastewater could be a long‐term, practical solution with the side benefits including wetland restorations and protection from wave erosion and storm surge.

Muskrat Abundance Responses to Water level Regulation Within Freshwater Coastal Wetlands

Muskrats (Ondatra zibethicus) are aptly described as “ecosystem engineers” for their influences associated with herbivory, house building, and movement within freshwater wetlands. Sensitivity to flow regime alteration via hydrologic regulation, however, may limit their populations and ability to facilitate wetland diversity and heterogeneity. Muskrat house surveys in coastal wetlands in tributaries (reference wetlands) subject to regional scale water level regulation were compared to treatment sites where local scale water-control structures were installed to alter the regulation effect. Data were used to develop a two-step model to predict wetland occupancy then house density to assess effects associated with proposed water level regulation plans. Field surveys indicated low house densities for cattail-dominated reference wetlands, and nearly 85% of houses located were in treatment sites. House distribution at reference sites was limited to channel edges, whereas houses at treatment sites were found throughout the floodplain. Occupancy of wetlands by muskrats was estimated by winter water depth, and fall water depth, and winter air temperature were selected as predictors of house density. Model validation indicated complete agreement for wetland occupancy, but density tended to be underestimated. Simulations provided a tool to evaluate water management plans and indicated that muskrat populations are suppressed under the current water level regulation regime.

Trajectories of vegetation‐based indicators used to assess wetland restoration progress

Temporal trends in attributes of restored ecosystems have been described conceptually as restoration trajectories. Measures describing the maturity or ecological integrity of a restoration site are often assumed to follow monotonically increasing trajectories over time and to eventually reach an asymptote representative of a reference ecosystem. This assumption of simple, predictable restoration trajectories underpins federal and state policies in the United States that mandate wetland restoration as compensation for wetlands damaged during development. We evaluated the validity of this assumption by tracking changes in 11 indicators of floristic integrity, often used to determine legal compliance, in 29 mitigation wetlands. Each indicator was expressed as a percentile relative to the distribution of that indicator among > 100 naturally occurring reference wetlands. Nonlinear regression was used to fit two alternative restoration trajectories to data from each site: an asymptotic (negative exponential) increase in the indicator over time and a peaked (double exponential) relationship. Depending on the particular indicator, between 48% and 76% of sites displayed trends that were at least moderately well described (R2 > 0.5) by one of the two models. Floristic indicators based on species richness, including native richness, number of native genera, and the floristic quality index, rapidly increased to asymptotes exceeding levels in a majority of reference wetlands. In contrast, indicators based on species composition, including mean coefficient of conservatism and relative importance of perennial species, increased very slowly. Thus, some indicators of restoration progress followed increasing trajectories and achieved or surpassed levels equivalent to high-quality reference sites within five years, whereas others appeared destined to either not reach equivalency or to take much longer than mitigation wetlands are typically monitored. Finally, some indicators of restoration progress, such as relative importance of native species, often increased over the first five to 10 years and then declined, which would result in a misleading assessment of progress if based on typical time scales of monitoring. Therefore, the assumption of simple, rapid, and predictable restoration trajectories that underlies wetland mitigation policy is unrealistic.

High species richness of Chironomidae (Diptera) in temporary flooded wetlands associated with high species turn-over rates

Species richness and species turn-over of Chironomidae was studied in irregularly flooded wetlands of the River Dalälven flood-plains in central Sweden. The chironomid fauna, sampled with emergence traps in six wetlands over six summers, contained as much as 135 species, and the cumulative species curves indicated that the regional species pool contain several more species. Recurrent irregular floods may have induced this high chironomid species richness and the high species turn-over in the temporary wetlands, as the dominance between terrestrial and aquatic species shifted between years. Half of the wetlands were treated with Bacillus thuringiensis var. israelensis (Bti) against larvae of the flood-water mosquito Aedes sticticus. These treatments had no significant effect on chironomid species richness, but there was a higher species turn-over between years of primarily low abundance species in the treated wetlands. The cumulative number of species was also higher in the Bti-treated experimental wetlands than in the untreated reference wetlands. Thus, Bti treatment against mosquito larvae seemed to have only small effects on chironomid species richness but seemed to increase the colonisation-extinction dynamics.

Variation in immune function, body condition, and feather corticosterone in nestling Tree Swallows ( Tachycineta bicolor) on reclaimed wetlands in the Athabasca oil sands, Alberta, Canada

In the Athabasca oil sands region of northern Alberta, mining companies are evaluating reclamation using constructed wetlands for integration of tailings. From May to July 2008, reproductive performance of 40 breeding pairs of tree swallows ( Tachycineta bicolor), plus growth and survival of nestlings, was measured on three reclaimed wetlands on two oil sands leases. A subset of nestlings was examined for i) feather corticosterone levels, ii) delayed-type hypersensitivity response, and iii) innate immune function. Nestlings on one of two wetlands created with oil sands process affected material (OSPM) were heavier and had greater wing-lengths, and mounted a stronger delayed-type hypersensitivity response compared those on the reference wetland. Corticosterone was significantly higher in male nestlings on one of two OSPM-containing wetland compared to the reference wetland. Body condition of 12-day-old female nestlings was inversely related to feather corticosterone. Under ideal weather conditions, reclaimed wetlands can support healthy populations of aerially-insectivorous birds.

The Influence of Microtopography on Soil Nutrients in Created Mitigation Wetlands

AbstractThis study explores the relationship between microtopography and soil nutrients (and trace elements), comparing results for created and reference wetlands in Virginia, and examining the effects of disking during wetland creation. Replicate multiscale tangentially conjoined circular transects were used to quantify microtopography both in terms of elevation and by two microtopographic indices. Corresponding soil samples were analyzed for moisture content, total C and N, KCl‐extractable NH4–N and NO3–N, and Mehlich‐3 extractable P, Ca, Mg, K, Al, Fe, and Mn. Means and variances of soil nutrient/element concentrations were compared between created and natural wetlands and between disked and nondisked created wetlands. Natural sites had higher and more variable soil moisture, higher extractable P and Fe, lower Mn than created wetlands, and comparatively high variability in nutrient concentrations. Disked sites had higher soil moisture, NH4–N, Fe, and Mn than did nondisked sites. Consistently low variances (Levene test for inequality) suggested that nondisked sites had minimal nutrient heterogeneity. Across sites, low P availability was inferred by the molar ratio (Mehlich‐3 [P/(Al + Fe)] < 0.06); strong intercorrelations among total C, total N, and extractable Fe, Al, and P suggested that humic–metal–P complexes may be important for P retention and availability. Correlations between nutrient/element concentrations and microtopographic indices suggested increased Mn and decreased K and Al availability with increased surface roughness. Disking appears to enhance water and nutrient retention, as well as nutrient heterogeneity otherwise absent from created wetlands, thus potentially promoting ecosystem development.

Breeding bird response to long-term wastewater discharge in a northern Michigan peatland

Researchers have monitored avian use of the Houghton Lake Sewer Authority wastewater treatment wetland and a nearby reference site from 1979 to 2007. Morning breeding bird surveys were conducted annually using 100-m belt transects. Annual species richness declined over the 29 years at the treatment site, but remained stable at the reference area. In a 12-year comparison of bird use of treated and reference wetland types, total bird density was highest in treated wetland consisting of cattail and cattail–wet meadow vegetation and lowest on leatherleaf and wet meadow reference types. Although species richness was highest in scrub-shrub wetland, treated wetland containing cattail marsh had significantly higher mean richness than types similar to pretreatment conditions (leatherleaf and wet meadow). Shannon diversity values in treated types dominated by cattail were similar to those in scrub-shrub wetland, but significantly higher than means observed in leatherleaf and wet meadow. Densities of Mallard, Green-winged teal, Virginia Rail, Sora, Wilson's Snipe, Marsh Wren, Swamp Sparrow, Red-winged Blackbird, and Common Grackle were highest at the treatment site in types containing cattail. Highest mean densities of Sedge Wren, Savannah Sparrow, and Northern Harrier occurred in wet meadow or leatherleaf types representative of pretreatment conditions.

Nitrogen retention versus methane emission: Environmental benefits and risks of large-scale wetland creation

Coastal eutrophication by nutrient fluxes from agricultural land to marine recipients is presently combated by measures such as the implementation of watershed-scale wetland creation programs aimed at nitrogen removal. Such created agricultural wetlands – termed ‘nitrogen farming wetlands’ (NFWs) – receive nitrogen (N) loads predominantly as nitrate, facilitating N removal by denitrification. However, the conversion of agricultural soils into waterlogged wetland area is likely to increase climate gas emissions, particularly methane (CH 4). There is thus a need to evaluate the benefits and risks of wetland creation at a large, watershed-scale. Here we investigate N retention and CH 4 emission originating from watershed-scale wetland creation in South Sweden, the relation between both processes, and how CH 4 emission depends on individual wetland parameters. We combine data from intensively studied reference wetlands with an extensive wetland survey to predict N retention and CH 4 emission with simple models, to estimate the overall process rates (large-scale effects) as well as spatial variation among individual NFWs. We show that watershed-scale wetland creation serves targeted environmental objectives (N retention), and that CH 4 emission is comparably low. Environmental benefit and risk of individual wetlands were not correlated, and may thus be managed independently. High cover of aquatic plants was the most important wetland property that suppressed CH 4 net production, potentially facilitating N retention simultaneously. Further, differences between wetlands in water temperature and wetland age seemed to contribute to differences in CH 4 net production. The nationally planned wetland creation (12,000 ha) could make a significant contribution to the targeted reduction of N fluxes (up to 27% of the Swedish environmental objective), at an environmental risk equaling 0.04% of the national anthropogenic climate gas emission.

Stable carbon isotopes as an indicator for soil degradation in an alpine environment (Urseren Valley, Switzerland)

Analyses of soil organic carbon (SOC) content and stable carbon isotope signatures (delta(13)C) of soils were assessed for their suitability to detect early stage soil erosion. We investigated the soils in the alpine Urseren Valley (southern central Switzerland) which are highly impacted by soil erosion. Hill slope transects from uplands (cambisols) to adjacent wetlands (histosols and histic to mollic gleysols) differing in their intensity of visible soil erosion, and reference wetlands without erosion influence were sampled. Carbon isotopic signature and SOC content of soil depth profiles were determined. A close correlation of delta(13)C and carbon content (r > 0.80) is found for upland soils not affected by soil erosion, indicating that depth profiles of delta(13)C of these upland soils mainly reflect decomposition of SOC. Long-term disturbance of an upland soil is indicated by decreasing correlation of delta(13)C and SOC (r </= 0.80) which goes in parallel with increasing (visible) damage at the site. Early stage soil erosion in hill slope transects from uplands to adjacent wetlands is documented as an intermediate delta(13)C value (-27.5 per thousand) for affected wetland soil horizons (0-12 cm) between upland (aerobic metabolism, relatively heavier delta(13)C of -26.6 per thousand) and wetland isotopic signatures (anaerobic metabolism, relatively lighter delta(13)C of -28.6 per thousand). Carbon isotopic signature and SOC content are found to be sensitive indicators of short- and long-term soil erosion processes.

Impacts of secondarily treated municipal effluent on a freshwater forested wetland after 60 years of discharge

Secondarily treated municipal effluent from Breaux Bridge, Louisiana has been discharged into the Cypriere Perdue forested wetland since the early 1950s. Approximately one million gallons per day (3,785 m−3 day−1) are discharged into the 1470 ha wetland, with average total nitrogen and phosphorus loading rates of 1.15 g N m−2 yr−1 and 0.31 g P m−2 yr−1, respectively. Vegetation and water quality of this wetland, along with a reference wetland, were monitored. Study sites were dominated by bald cypress and water tupelo, and species composition did not change significantly during the time of monitoring. Mean litterfall was higher near the effluent discharge point compared to sites located further away or the reference site. Mean stem growth was lower at the site furthest from the discharge point compared to the other sites. Nutrient concentrations measured at the site where water exits the assimilation area and at the reference site were not significantly different. Removal efficiencies for total nitrogen and phosphorus are typical of other forested wetlands receiving treated effluent in Louisiana, ranging between 65 and 90%. These results demonstrate that this wetland assimilates nutrients to background concentrations even after 60 years of operation, stimulating productivity, and causing no measurable impacts to the wetland or to the river into which the water eventually flows.

Efficacy of Natural Wetlands to Retain Nutrient, Sediment and Microbial Pollutants

Wetlands can improve water quality through natural processes including sedimentation, nutrient transformations, and microbial and plant uptake. Tailwater from irrigated pastures may contribute to nonpoint source water pollution in the form of sediments, nutrients, and pathogens that degrade downstream water quality. We examined benefits to water quality provided by a natural, flow-through wetland and a degraded, channelized wetland situated within the flood-irrigation agricultural landscape of the Sierra Nevada foothills of Northern California. The non-degraded, reference wetland significantly improved water quality by reducing loads of total suspended sediments, nitrate, and Escherichia coli on average by 77, 60, and 68%, respectively. Retention of total N, total P, and soluble reactive P (SRP) was between 35 and 42% of loads entering the reference wetland. Retention of pollutant loads by the channelized wetland was significantly lower than by the reference wetland for all pollutants except SRP. A net export of sediment and nitrate was observed from the channelized wetland. Decreased irrigation inflow rates significantly improved retention efficiencies for nitrate, E. coli, and sediments in the reference wetland. We suggest that maintenance of these natural wetlands and regulation of inflow rates can be important aspects of a best management plan to improve water quality as water runs off of irrigated pastures.

Comparison of Function of Created Wetlands of Two Age Classes in Central Pennsylvania

Hydrogeomorphic (HGM) functional assessment models were used to assess whether function in created wetlands of two ages (1 year old and >12 years old) was equivalent to that of natural (reference) mainstem floodplain wetlands. Reference wetlands scored higher than both created age classes for providing energy dissipation and short-term surface water storage. Reference wetlands scored higher in maintaining native plant community and structure than 1-year-old sites, and 12-year-old wetlands scored higher than reference sites for providing vertebrate habitat structure. Analysis of individual model variables showed that reference wetlands had greater vegetative biomass and higher soil organic matter content than both created wetland age classes. Created wetlands were farther from natural wetlands and had smaller mean forest patch sizes within a 1-km-radius circle around the site than did the reference sites, indicating less hydrologic connectivity. Created wetlands also had less microtopographic variation than reference wetlands. The 1-year-old created sites were placed in landscape settings with greater land use diversity and road density than reference sites. The 12-year-old sites had a higher gradient and a higher percentage of their surrounding area in urban land use. These results show that the created wetlands were significantly structurally different (if not functionally so) from reference wetlands even after 12 years. The most profound differences were in hydrology and the characteristics of the surrounding landscape. More attention needs to be focused on placing created wetlands in appropriate settings to encourage proper hydrodynamics, eliminate habitat fragmentation, and minimize the effects of stressors to the site.

English

In watersheds of the mid-Atlantic region of the US where sulfide spoils occur from mining operations, geochemical reactions develop additional acids in the soil and water supply. The resulting condition lowers ambient pH to very low values (2 to 4 SU). The low pH impairs the soil chemistry and water quality to the extent that native flora and fauna can not survive on the site. This work presents the design and evaluation of remedial work implemented to abate acid mine drainage from a sulfide mine (Valzinco Mine) in the Piedmont Provence of Virginia, USA. Water quality conditions were measured before and after the remediation work, and documented the re-establishment and abundance of native wetland and aquatic vegetation within the site. Data showed that average pH increased from 3.4 to 5.1 and a decrease in total dissolved solids (Fe, Al, Zn, Pb, Cu, Cd, and SO4 2- ) over the study period. Initial wetland vegetation, both planted and volunteer, quickly colonized the site with an average ground cover of >74% after five years. Aquatic vegetation cover averaged >50% after 2 years and many plots had coverage >100%. Composition, species richness, and abundance of the new vegetation communities was similar to that of near-by reference (un-affected by mine activities) wetland (>75%, 6.0 spp. m -2 vs. 5.5 spp. m -2 , average cover 74% vs. 67%, respectively). Two amphibians (southern leopard frog, pickerel frog) and two aquatic reptiles (brown water snake and northern water snake) were captured on the site during the fifth year, indicating a return of herpatifauna to the wetland and aquatic communities. We conclude that the increase in pH, decline in total dissolved minerals, success of the re- vegetation of the site, and return of the reptiles to the site, is a strong indication that the remedial work successfully restored the soil and water chemistry closer to pre- mining conditions. Therefore, we suggest that the successful restoration of this site was based on sound hydrological and biogeochemical principles that can be applied to restoration efforts in other acid damaged watersheds in the mid-Atlantic region.

Determining the feasibility and cost of an ecologically-based design for a mitigation wetland in central Pennsylvania, USA

Studies indicate that mitigation wetlands are structurally and functionally different, not only from the wetlands they are intended to replace, but also from wetlands they ought to resemble based upon their position in the landscape. The objective of this study was to revisit a single wetland mitigation project to determine if a different, ecologically-based, design could have been developed in place of the original, at comparable cost. We selected a wetland in Pennsylvania (one of several built as mitigation totaling more than 12 ha) built during mitigation efforts for a major highway based upon available background data, the construction document package, and itemized costs. We prepared an alternative design using the original pre-construction site survey as a base map and local reference wetlands to inform the design process. We anticipated that the alternative design would cost less than the original, but due to site conditions and the objective of mimicking a natural wetland, much more earth needed to be excavated in the alternative design than anticipated. The cost of excavation, coupled with the added expense of hauling surplus fill off site, proved to be expensive. Nevertheless, other design differences, such the absence of water control structures, lack of instant habitat improvement devices, omission of an impermeable soil layer, and application of a simpler planting strategy, allowed for considerable cost savings.

Analytic Method to Derive Wetland Stage-Storage Relationships Using GIS Areas

The relationship between the depression area (A) , volume (V) , and depth of water (h) for wetlands, ponds, and lakes is often required for model studies. Area-depth (A-h) and volume-depth (V-h) relationships for wetlands, ponds, and lakes, which are important inputs to hydrologic models can be developed from detailed surveys and/or bathymetric maps that are costly and labor intensive to produce, or the use of simple geometric models. An analytical approach is introduced to describe wetland stage-storage (V-h) relationships using a single shape parameter, simple geometric data available from geographic information system coverages or field studies, and a power-function model. The dimensionless shape parameter defines the wetland prismatic conic shape, and together with the reference wetland pool area and associated maximum pool depth defines the V-h relationship to a high degree of accuracy. Shape parameters were developed for 42 wetlands to generate V-h relationships for each wetland. The study findings ...

Short-Term Seasonal Changes in Parasite Community Structure in Northern Leopard Froglets (Rana pipiens) Inhabiting Agricultural Wetlands

Parasite community structure can change seasonally with shifts in host habitat and in diet. However, anthropogenic activity may influence the natural changes in transmission dynamics of different parasite species. Effects of seasonal and agricultural activity on the parasite communities of newly metamorphosed northern leopard frogs (Rana pipiens) were investigated in July and September 2001 in 5 wetlands, 3 of which were exposed to pesticide runoff from surrounding agriculture. Nineteen parasite taxa were found. Component community richness was consistently high at the pristine reference wetland, whereas the communities at a managed reference wetland remained depauperate. Infracommunity richness increased throughout the season, but more so in frogs resident in agricultural wetlands. Digeneans using frogs as intermediate hosts dominated the communities, although many species were much lower in abundance in September, suggesting mortality of heavily infected frogs. Mean abundance of Haematoloechus spp. was positively related to that of odonate naiads in the frog diet, which appeared to reflect differential second intermediate host availability between reference and agricultural wetlands. Although virtually absent from wetlands in July just after frog metamorphosis, monoxenous nematodes were more prevalent and abundant at agricultural wetlands as the season progressed. Our results suggest that agricultural activity may further facilitate the transmission of monoxenous nematodes as frogs become more terrestrial.

Hydraulic geometry and microtopography of tidal freshwater forested wetlands and implications for restoration, Columbia River, U.S.A.

In many coastal areas, diking has severed the lateral connectivity between river channels and tidal freshwater floodplain forests that, historically, were shaped by riverine and oceanic hydrologic processes and local surficial geology. This paper assesses geomorphological aspects of Picea sitchensis (Sitka spruce) reference wetlands and restoration sites on the West Coast of North America. Multi-scale methods from fluvial and estuarine sciences included field surveys and spatial analysis of Light Detection and Ranging (LiDAR) data. At reference wetlands, correlations between channel cross-sectional area at outlet and catchment-scale features (catchment area, total length of channels) were consistent with previously published hydraulic geometry of two tidal salt marsh systems. Hydrologic reconnection restoration actions on agricultural lands – dike breaching, culvert installation, and tide gate replacement – all affected channel cross-sectional geometry. Diked land had subsided and lost microtopographic features associated with large wood during agricultural use, while channel density remained comparable to reference wetlands. Thus, at restoration sites, a greater area-time inundation index and frequency of inundation increased both sedimentation rates and channel cross-sectional areas when compared to reference wetlands. Such site-scale restoration affects ecosystem processes and produces measurable patterns in hydraulic geometry and channel morphology.