Article

Plant Species Indicators of Physical Environment in Great Lakes Coastal Wetlands

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Abstract

Plant taxa identified in 90 U.S. Great Lakes coastal emergent wetlands were evaluated as indicators of physical environment. Canonical correspondence analysis using the 40 most common taxa showed that water depth and tussock height explained the greatest amount of species-environment interac-tion among ten environmental factors measured as continuous variables (water depth, tussock height, lati-tude, longitude, and six ground cover categories). Indicator species analysis was used to identify species-environment interactions with categorical variables of soil type (sand, silt, clay, organic) and hydrogeomorphic type (Open-Coast Wetlands, River-Influenced Wetlands, Protected Wetlands). Of the 169 taxa that occurred in a minimum of four study sites and ten plots, 48 were hydrogeomorphic indicators and 90 were soil indicators. Most indicators of Protected Wetlands were bog and fen species which were also organic soil indicators. Protected Wetlands had significantly greater average coefficient of conservatism (C) values than did Open-Coast Wetlands and River-Influenced Wetlands, but average C values did not differ significantly by soil type. Open-Coast and River-Influenced hydrogeomorphic types tended to have sand or silt soils. Clay soils were found primarily in areas with Quaternary glaciolacustrine deposits or clay-rich tills. A fuller understanding of how the physical environment influences plant species distribution will improve our ability to detect the response of wetland vegetation to anthropogenic activities. INDEX WORDS: Indicator species, soil texture, organic soil, hydrogeomorphic, tussock, coastal wetlands.

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... Protected wetlands (n ¼ 28) were hydrologically connected with the Great Lakes, but were protected from the full force of wave action by their location behind a sand spit, barrier beach, bayhead, or dike. Specific study wetlands and their assigned geomorphic types are listed in Johnston et al. (2007). Plant sampling was conducted in 1 3 1 m quadrats distributed along randomly placed transects within areas of emergent herbaceous wetland vegetation in the study wetlands selected. ...
... Plant sampling was conducted in 1 3 1 m quadrats distributed along randomly placed transects within areas of emergent herbaceous wetland vegetation in the study wetlands selected. Transects were established with a geographic information system (GIS) prior to field campaigns, using a program called Sample (Quantitative Decisions, Rosemont, Pennsylvania, USA) to randomize transect placement (Johnston et al. 2007). Transects were placed in areas mapped by national and state wetland inventories as emergent wetland vegetation. ...
... Both are subcanopy species that are often overlooked because they are so diminutive, yet they were two of the most frequently occurring species in our study, found in more than half of the 90 wetlands studied. Neither species was a dominant plant () nor an indicator of soil type (Johnston et al. 2007), but both had utility as indicators of anthropogenic stress. Evaluating individual species allows comparisons with experimental studies of species habitat preferences and competitive abilities. ...
Article
Emergent plants can be suitable indicators of anthropogenic stress in coastal wetlands if their responses to natural environmental variation can be parsed from their responses to human activities in and around wetlands. We used hierarchical partitioning to evaluate the independent influence of geomorphology, geography, and anthropogenic stress on common wetland plants of the U.S. Great Lakes coast and developed multi-taxa models indicating wetland condition. A seven-taxon model predicted condition relative to watershed-derived anthropogenic stress, and a four-taxon model predicted condition relative to within-wetland anthropogenic stressors that modified hydrology. The Great Lake on which the wetlands occurred explained an average of about half the variation in species cover, and subdividing the data by lake allowed us to remove that source of variation. We developed lake-specific multi-taxa models for all of the Great Lakes except Lake Ontario, which had no plant species with significant independent effects of anthropogenic stress. Plant responses were both positive (increasing cover with stress) and negative (decreasing cover with stress), and plant taxa incorporated into the lake-specific models differed by Great Lake. The resulting models require information on only a few taxa, rather than all plant species within a wetland, making them easier to implement than existing indicators.
... An important exception is an analysis of 62 marshes on the Canadian side of the Great Lakes by Lougheed and coworkers (2001), but that study focused on macrophyte beds with standing water above the soil surface, and did not consider herbaceous wet meadows, fens, or bogs. Our goal is to develop plant community metrics to evaluate the condition of U.S. Great Lakes coastal wetlands, using vegetation data that we collected at 90 wetlands for the Great Lakes Environmental Indicators (GLEI) project (Johnston et al. 2007, Niemi et al. 2007). Specific objectives are to: (1) define Great Lakes wetland plant communities based on multivariate analyses and (2) relate those plant assemblages to anthropogenic and physical environmental variables using CART analysis. ...
... Vegetation sampling was conducted from 2001 to 2003 and was restricted to the months of July and August to ensure that most of the vegetation could be identified and peak annual growth observed. Site characteristics and details of vegetation sampling methods are described by Johnston et al. (2007 Johnston et al. ( , 2008). ...
... Two wetland hydrogeomorphic classifications were used as categorical data (Table 1). The three GLEI hydrogeomorphic classes (protected wetlands, riverinfluenced wetlands, and open coast wetlands) were applied as in Johnston et al. (2007). We also applied 12 hydrogeomorphic classes defined by Albert and coworkers (2005) and mapped by the Great Lakes Coastal Wetlands Consortium (available online). ...
Article
Assessment of vegetation is an important part of evaluating wetland condition, but it is complicated by the variety of plant communities that are naturally present in freshwater wetlands. We present an approach to evaluate wetland condition consisting of: (1) a stratified random sample representing the entire range of anthropogenic stress, (2) field data representing a range of water depths within the wetlands sampled, (3) nonmetric multidimensional scaling (MDS) to determine a biological condition gradient across the wetlands sampled, (4) hierarchical clustering to interpret the condition results relative to recognizable plant communities, (5) classification and regression tree (CART) analysis to relate biological condition to natural and anthropogenic environmental drivers, and (6) mapping the results to display their geographic distribution. We applied this approach to plant species data collected at 90 wetlands of the U.S. Great Lakes coast that support a variety of plant communities, reflecting the diverse physical environment and anthropogenic stressors present within the region. Hierarchical cluster analysis yielded eight plant communities at a minimum similarity of 25%. Wetlands that clustered botanically were often geographically clustered as well, even though location was not an input variable in the analysis. The eight vegetation clusters corresponded well with the MDS configuration of the data, in which the first axis was strongly related (R2 = 0.787, P < 0.001) with floristic quality index (FQI) and the second axis was related to the Great Lake of occurrence. CART models using FQI and the first MDS axis as the response variables explained 75% and 82% of the variance in the data, resulting in 6-7 terminal groups spanning the condition gradient. Initial CART splits divided the region based on growing degree-days and cumulative anthropogenic stress; only after making these broad divisions were wetlands distinguished by more local characteristics. Agricultural and urban development variables were important correlates of wetland biological condition, generating optimal or surrogate splits at every split node of the MDS CART model. Our findings provide a means of using vegetation to evaluate a range of wetland condition across a broad and diverse geographic region.
... An important exception is an analysis of 62 marshes on the Canadian side of the Great Lakes by Lougheed and coworkers (2001), but that study focused on macrophyte beds with standing water above the soil surface, and did not consider herbaceous wet meadows, fens, or bogs. Our goal is to develop plant community metrics to evaluate the condition of U.S. Great Lakes coastal wetlands, using vegetation data that we collected at 90 wetlands for the Great Lakes Environmental Indicators (GLEI) project (Johnston et al. 2007, Niemi et al. 2007). Specific objectives are to: (1) define Great Lakes wetland plant communities based on multivariate analyses and (2) relate those plant assemblages to anthropogenic and physical environmental variables using CART analysis. ...
... Vegetation sampling was conducted from 2001 to 2003 and was restricted to the months of July and August to ensure that most of the vegetation could be identified and peak annual growth observed. Site characteristics and details of vegetation sampling methods are described by Johnston et al. (2007 Johnston et al. ( , 2008). ...
... Two wetland hydrogeomorphic classifications were used as categorical data (Table 1). The three GLEI hydrogeomorphic classes (protected wetlands, riverinfluenced wetlands, and open coast wetlands) were applied as in Johnston et al. (2007). We also applied 12 hydrogeomorphic classes defined by Albert and coworkers (2005) and mapped by the Great Lakes Coastal Wetlands Consortium (available online). ...
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The wetland complex is the functional ecological unit of the prairie pothole region (PPR) of central North America. Diverse complexes of wetlands contribute high spatial and temporal environmental heterogeneity, productivity, and biodiversity to these glaciated prairie landscapes. Climate- warming simulations using the new model WETLANDSCAPE (WLS) project major reductions in water volume, shortening of hydroperiods, and less-dynamic vegetation for prairie wetland complexes. The WLS model portrays the future PPR as a much less resilient ecosystem: The western PPR will be too dry and the eastern PPR will have too few functional wetlands and nesting habitat to support historic levels of waterfowl and other wetland-dependent species. Maintaining ecosystem goods and services at current levels in a warmer climate will be a major challenge for the conservation community.
... Our estimate of denitrification (DeNIT) rates (7-30 μg N g −1 d −1 or 2-300 mg N m −2 d −1 ) was more than two orders of magnitude greater than previous estimates in two backwater wetlands of the SLRE in May and August, one in Pokegama River ("bay") and the other near the head of the SLRE ("river") (b0.05 μg N g −1 d −1 ; Johnston et al., 2001). The shallow depths (b0.5 m) of sites within emergent vegetation beds and the low water column and sediment NO 3 − -concentrations (5-40 μg/L) may account for the discrepancy. ...
... Late summer declines in water column NO 3 − have been shown to supersede the positive effects of temperature on DeNIT rates (Holmes et al., 1996;Rysgaard et al., 1995;Strauss et al., 2006). Concentration of NO 3 − in the SLRE typically declines through the summer (Johnston et al., 2001), but this effect was overwhelmed by the 2012 June flood: NOx-Nconcentration in July 2012 was more than twice that of July 2011. Despite comparable water temperatures, greater NOx-N-concentration, higher NIT rates, and deeper water depths in July 2012 than in 2011, DeNIT rates in the bay and harbor were three to six times lower in July 2012, likely a consequence of the 2012 flood. ...
... The SLRE denitrifying community had a stronger response to NO 3 − -than to C-amendments (i.e., DeNIT N N DeNIT C ). When both amendments were added, potential rates (i.e., DEA) were two to two hundred times higher than the base rate, which is comparable to findings elsewhere (Johnston et al., 2001;Seitzinger, 1994). Denitrifying enzyme activity rates in the SLRE (0-8 mg N kg − 1 h − 1 or 500-1100 mg N m − 2 d − 1 ) were similar to DEA rates in the backwaters of the Upper Mississippi River (960-2800 mg N m − 2 d − 1 ; Richardson et al., 2004) and in upland, riparian, and wetland sediments (0-6 mg N kg − 1 h − 1 ; White and Reddy, 1999). ...
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Inorganic nitrogen (N) transformations and removal in aquatic sediments are microbially mediated, and rates influence N-transport. In this study we related physicochemical properties of a large Great Lakes embayment, the St. Louis River Estuary (SLRE) of western Lake Superior, to sediment N-transformation rates. We tested for associations among rates and N-inputs, vegetation biomass, and temperature. We measured rates of nitrification (NIT), unamended base denitrification (DeNIT), and potential denitrification [denitrifying enzyme activity (DEA)] in 2011 and 2012 across spatial and depth zones. In vegetated habitats, NIT and DeNIT rates were highest in deep (ca. 2 m) water (249 and 2111 mg N m− 2 d− 1, respectively) and in the upper and lower reaches of the SLRE (> 126 and 274 mg N m− 2 d− 1, respectively). Rates of DEA were similar among zones. In 2012, NIT, DeNIT, and DEA rates were highest in July, May, and June, respectively. System-wide, we observed highest NIT (223 and 287 mg N m− 2 d− 1) and DeNIT (77 and 64 mg N m− 2 d− 1) rates in the harbor and from deep water, respectively. Amendment with NO3− enhanced DeNIT rates more than carbon amendment; however, DeNIT and NIT rates were inversely related, suggesting the two processes are decoupled in sediments. Average proportion of N2O released during DEA (23–54%) was greater than from DeNIT (0–41%). Nitrogen cycling rates were spatially and temporally variable, but we modeled how alterations to water depth and N-inputs may impact DeNIT rates. A large flood occurred in 2012 which temporarily altered water chemistry and sediment nitrogen cycling.
... Wetland's ecotones are amongst the richest life supporting ecosystem and they are most threatened due to various biotic stresses (Singh, 2013). Vegetation refers to the great diversity of plant species which occur in assemblages over the face of the earth (Johnston et al., 2007). Floral assessment is an important criterion for the assessment of life forms and habitat for an area (Klosowski, 1993). ...
... Change in land and water use, water discharge, environmental condition and structure can all have profound effects on the functioning of a lake (Olubode et al., 2011). An understanding of individual plant species is the first step in developing indicators of the ecological condition of a lake (Johnston et al., 2007) because the indices based on plant assemblages rely on the cumulative behavior of individual species (Klosowski, 1993). The lakeshore affects in the littoral zone and lake ecosystems (Lu et al., 2016) which provides physical structure, alters water movements and hydrological processes and affects the transport of organic materials within the aquatic environment (Teneva et al., 2014). ...
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Land-water interfaces of lakes are highly dynamic and are responsible for the stability and maintenance of ecosystems. This study was carried out to understand the ecotone vegetation and the physico-chemical characteristics of waters of Begnas and Rara lakes of Nepal. For vegetation survey, line transects (perpendicular bi-sector to lake boundary), were used along the lake boundaries at an interval of 500 m; three quadrats of 1 m x 1 m size were laid on each line transect (off shore, boundary line, and on shore). All vegetation species in the sample quadrates were recorded. For probing water quality, lakes were divided into three blocks, then sampling was conducted on a consecutive day. Physico-chemical parameters-temperature, pH, electric conductivity (EC), dissolved oxygen (DO), total dissolved solid (TDS), ammonia, and nitrate-were measured. A total of 55 species under 38 families and 28 orders were recorded from ecotone of Begnas lake. In Rara lake, 56 species of 41 families and 22 orders were recorded. Poaceae was the dominant largest family in Begnas which was followed by Asteraceae. In Rara lake, Rosaceae was the dominant family which was followed by Pinaceae. Temperature, pH, and DO values decreased with depth, but EC and TDS e increased with depth, in both Begnas and Rara lakes. Ammonia and Nitrate were below the detectable limit of the instrument, indicating low nutrient contents of both lakes. The study established the baseline information about the diversity of ecotone vegetation; both the lakes show clear changes in physio-chemical parameters with lake depths.
... For site selection, land-based stress was quantified in a geographic information system (GIS) for 762 coastal segmentsheds that encompassed the entire U.S. basin; each segment-shed consisted of the land area that drained into a segment of coastline extending in either direction from 2nd-order or larger streams to one-half the distance to the adjacent stream. Since the original selection of the sites by Danz et al. (2005), and also described in detail by Johnston et al. (2007), more detailed watersheds were delineated specific to each sampled site (Hollenhorst et al. 2007). Sampled sites were represented within the GIS by polygons encompassing the sampling points for all GLEI indicator groups at a selected locale. ...
... A total of 14 Lake Huron wetlands were sampled for wetland vegetation. Sampling was done in 1 m × 1 m plots distributed along randomly placed transects (Bourdaghs et al., 2006; Johnston et al., 2007). Within each plot all vascular plant species were identified to the lowest taxonomic division possible, and percent cover was estimated visually for each taxon according to modified Braun- Blanquet cover class ranges: <1%, 1 to <5%, 5 to <25%, 25 to <50%, 50 to <75%, 75 to 100%. ...
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Our overall goal was to develop indicators that both estimate ecological condition and suggest plausible causes of ecosystem degradation across the U.S. Great Lakes coastal region. Here we summarize data gathered along the U.S. Lake Huron coastline for breeding bird, diatom, fish, invertebrate, and wetland plant communities. We sampled these biotic communities on 88 sites in Lake Huron coastal wetlands, uplands, estuaries/bays, and high-energy shorelines. The sites were selected as part of a larger, stratified random design for the entire U.S. Great Lakes coastal region using gradients of anthropogenic stress that incorporated over 200 stressor variables (e.g. agriculture, land cover, human populations, and point source pollution). The U.S. Lake Huron coastal region exemplified wide variation in human-related stress relative to the entire U.S. Great Lakes coast. In general, levels of stress decreased from south to north partly reflecting the change in climate and physiography, but also due to the greater human influences in the southern region as compared with the north. The primary stressors in the southern region are due to agriculture and human development, while the northern region has substantially less agriculture and less human population. The biotic communities sampled were strongly related to the environmental stress gradients, especially agriculture and urbanization. The following indicators were developed based on responses to stress: 1) an index of biological condition for breeding bird communities corresponding to land use, 2) a diatom-inferred total phosphorus indicator corresponding to water quality, 3) exotic fish (carp [Cyprinus carpio] and goldfish [Carassius auratus]) corresponding to agriculture, and 4) a multi-taxa index for wetland plants corresponding to a cumulative stress index. These communities can all serve as useful indicators of the ecological condition of the Lake Huron coast. The ecological indicators provide a baseline on selected conditions for the U.S. Lake Huron coastal region and a means to detect change over time.
... Satellite remote sensing has many advantages for mapping wetlands, including frequent acquisition, repeat coverage for monitoring changing conditions, and low image cost in comparison to high-altitude photography (Ozesmi and Bauer 2002). The ability to remotely identify dominant wetland plant species is desirable, because plant species are indicators of wetland condition (Johnston et al. 2007a). It would be particularly useful to identify the presence and spread of invasive plant species that displace native vegetation and degrade wetland habitat values (Madden 2004). ...
... Because we had minimal knowledge of the site prior to image classification, we opted to use unsupervised classification, which is recommended when not much is known about the data before classification (Leica Geosystems 2003). We performed an unsupervised classification (ISOJohnston et al. 2007a). The classification distinguished three monodominant genera (Phragmites australis, Typha spp., and Nelumbo lutea), three multi-genera plant communities (wet meadow, non persistent emergents, and woody vegetation), and two unvegetated cover types (water and soil). ...
Article
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QuickBird multispectral satellite images taken in September 2002 (peak biomass) and April 2003 (pre-growing season) were used to map emergent wetland vegetation communities, particularly invasive Phragmites australis and Typha spp., within a diked wetland at the western end of Lake Erie. An unsupervised classification was performed on a nine-layer image stack consisting of all four spectral bands from both dates plus a September Normalized Difference Vegetation Index image. The resulting eight cover classes distinguished three monodominant genera (Phragmites australis, Typha spp., Nelumbo lutea), three multigenera plant communities (wet meadow, other non persistent emergents, woody vegetation), and two unvegetated cover types (water, bare soil). Field validation at 196 data points yielded an overall classification accuracy of 62%, with producer’s accuracy for the eight individual classes ranging from 41 to 91% and user’s accuracy from 17 to 90%. Three-fourths of areas designated as Phragmites were correctly mapped, but 14% were found to be cattail (Typha) during field validation. Lotus (Nelumbo lutea) beds were accurately mapped on multiseason imagery (producer’s accuracy = 91%); these beds had not yet emerged above water in April, but were fully developed in September. Other types of non persistent vegetation were confused with managed areas in which vegetation had been cut and burned to control invasive Phragmites. Multiseason QuickBird imagery is promising for distinguishing certain wetland plant species, but should be used with caution in highly managed areas where vegetation changes may reflect human alterations rather than phenological change.
... Plant species distributions have a long history of use as ecological indicators. Johnston et al. (2007a) use wetland plant species as indicators of the physical environment of 90 wetlands in the U.S. Great Lakes coast. Forty common plant species out of 192 species were the most important in describing these wetland environments. ...
... Remote sensing and geographic information systems will be essential tools in future development of environmental indicators. Johnston et al. (2007b) show how past aerial photography can be used with contemporary satellite imagery to identify land use change over a 60-year period in a 100 km 2 area in the western end of Lake Erie. In contrast, Tulbure et al. (2007) track the invasion of Phragmites and non-native Typha over a 5-year period as water levels changed at Point au Sable, Green Bay, Wisconsin. ...
Article
The Great Lakes coastal region is a dynamic area at the interface between land and water. It is heavily influenced by the magnitude of the large lakes themselves, by natural abiotic and biotic processes in the watershed, and especially by human activity. This special issue contains a series of 21 papers that are organized into four major themes: 1) landscape characterization and coastal linkage, 2) integration, 3) indicator development, and 4) supporting information. The results of these papers emphasize that many environmental response signals are linked to their physiobiogeographic location in the basin and with human activity in coastal watersheds or in the immediate coastal margin. If lake levels continue to fluctuate and decline, if the climate continues to warm, if agricultural activity expands, if exotic species continue to invade, and if the human population density in the watershed increases, then environmental indicators of the Great Lakes coastal region reported here will point to further degradation of water quality and native amphibian, bird, diatom, fish, macroinvertebrate, and wetland plant communities. These environmental indicators are benchmarks for the current conditions of the Great Lakes coastal region and provide measurable endpoints to assess the success of future management, conservation, protection, and restoration of this important resource.
... Soil parameters that are exclusively significant to linear locations include texture and TOC. Texture is a soil property that can influence the composition of plant communities (Brady 1990) and therefore, a plant community such as a wetland plant communities can indicate soil type (Johnston et al. 2007). Distinct plant communities are also associated with the accumulated organic matter and high TOC of peatlands, with certain species found in this wetland type only (Mitsch and Gosselink 1993). ...
... Emergent vegetation was sampled in 26 Lake Superior coastal wetlands. Sampling was done by visual cover estimation in 1 × 1-m plots distributed along randomly placed transects, using a protocol described by Johnston et al. (2007Johnston et al. ( , 2008Johnston et al. ( , 2009b. A data matrix was constructed of taxa cover for each of the 26 sites; taxa found at a minimum of two sites were retained. ...
Article
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Biological indicators can be used both to estimate ecological condition and to suggest plausible causes of ecosystem degradation across the U.S. Great Lakes coastal region. Here we use data on breeding bird, diatom, fish, invertebrate, and wetland plant communities to develop robust indicators of ecological condition of the U.S. Lake Superior coastal zone. Sites were selected as part of a larger, stratified random design for the entire U.S. Great Lakes coastal region, covering gradients of anthropogenic stress defined by over 200 stressor variables (e.g. agriculture, altered land cover, human populations, and point source pollution). A total of 89 locations in Lake Superior were sampled between 2001 and 2004 including 31 sites for stable isotope analysis of benthic macroinvertebrates, 62 sites for birds, 35 for diatoms, 32 for fish and macroinvertebrates, and 26 for wetland vegetation. A relationship between watershed disturbance metrics and 15N levels in coastal macroinvertebrates confirmed that watershed-based stressor gradients are expressed across Lake Superior's coastal ecosystems, increasing confidence in ascribing causes of biological responses to some landscape activities. Several landscape metrics in particular—agriculture, urbanization, human population density, and road density—strongly influenced the responses of indicator species assemblages. Conditions were generally good in Lake Superior, but in some areas watershed stressors produced degraded conditions that were similar to those in the southern and eastern U.S. Great Lakes. The following indicators were developed based on biotic responses to stress in Lake Superior in the context of all the Great Lakes: (1) an index of ecological condition for breeding bird communities, (2) diatom-based nutrient and solids indicators, (3) fish and macroinvertebrate indicators for coastal wetlands, and (4) a non-metric multidimensional scaling for wetland plants corresponding to a cumulative stress index. These biotic measures serve as useful indicators of the ecological condition of the Lake Superior coast; collectively, they provide a baseline assessment of selected biological conditions for the U.S. Lake Superior coastal region and prescribe a means to detect change over time.
... Further, whereas species presence or probability of occurrence may serve well as indicators, assessment of physical habitat for wildlife might be less time-consuming than wildlife surveys. Most wetland habitat indicators (Thoma, 2006; Johnston et al., 2007) have measured the responses of habitat to anthropogenic stressors, and may not reflect the support of biota. The development of wetland habitat-wildlife relationships would help establish integrated wildlife assessments using habitat characteristics. ...
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Significant ecosystem services derive from the coastal wetlands of the Laurentian Great Lakes even though two-thirds of the original coastal wetlands have been lost since European settlement, and the remaining 126,000 ha of U.S. coastal wetlands and ≥70,000 ha of Canadian wetlands are affected by anthropogenic stressors. Published information indicates that wildlife habitat, fisheries support, and water quality improvement are significant ecosystem services provided by Great Lakes coastal wetlands that should be strongly considered during management decision making. 30 species of waterfowl, 155 breeding bird species, and 55 species of reptiles and amphibians are supported by coastal wetland habitats across the Basin. Nearly all sport and commercial Great Lakes fish species use coastal wetlands for life-cycle functions, and Great Lakes food webs are supported by wetland export of young sport and forage fish. Biological responses indicate declines in the wildlife and fishery services with increasing levels of anthropogenic disturbance. Extrapolation from a single well-studied system suggests that, Basin-wide, coastal wetlands may retain nearly 4000 tonnes P and 53,000 tonnes N per year, but additional studies are needed to support these estimates and determine stressor effects. Coastal wetlands appear to retain sediments over long time scales, but may either retain or release sediments during storm events. Extrapolation of carbon sequestration from other wetland types suggests that less than 90 g C yr might be retained across the Basin. Wild rice production provides a culturally important ecosystem service, and coastal protection may be locally significant where fringing wetland remain. To support management decisions, quantitative relationships between specific stressors or land use practices and the delivery of ecosystem services are needed, as are ecosystem service indicators to measure those responses.
... Costello (1936) also observed variation in C. stricta tussock diameter and attributed it to a range of possible factors, including the successional stage of the site, soil saturation, fire history, or rodent grazing. Tussock height at our reference sites in southern Wisconsin fell within the range of those observed by Peach and Zedler (2006), but were slightly shorter than the mean height of C. stricta tussocks (18.8 cm) that Johnston et al. (2007) observed in their survey of 90 Great Lakes coastal wetlands, as well as those measured by Crain and Bertness (2005) in a tidal wetland in Maine (~25 cm). Tussocks at Ref 4 were 63 % as tall as Refs 1-3, either younger age or partial burial by inflowing sediments could reduce height (Werner and Zedler 2002). ...
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Tussock-forming plants are globally widespread and enhance ecosystem services. We hypothesized that tussocks of Carex stricta store carbon (C) in addition to enhancing microtopography and biodiversity. We characterized tussock size, composition, and carbon pools associated with three undisturbed C. stricta-dominated tussock meadows in the Upper Midwest, USA. Remnant meadow tussocks were tall (17.2 cm), voluminous (4,113 cm3), and largely organic (95 %), indicating their ability to accumulate organic matter and store carbon. Tussocks were the second largest C pool (next to soil) in these ecosystems; they comprised 41–62 % of total biomass C. Using bomb 14C dating, we estimated that reference-site tussocks were over 50 years old. Their long-term persistence is consistent with lower leaf decomposition rates on tussocks (k = 0.26 years−1) than in tussock interspaces (k = 0.39 years−1). An urban tussock meadow had tussocks that were shorter than those of remnant sites, but less dense than a restored meadow. The restored meadow (≤15 years) had smaller, structurally distinct tussocks that stored less C. Among the five sites, C stocks were lowest in the urban and restored meadows, supporting the need to conserve existing C stores in remnant meadows and to restore tussock sedge for multiple ecosystem services.
... The North American Great Lakes (Lakes Superior, Michigan, Huron, Erie, and Ontario) have been subjected to elevated pollutions due to intensive human activities [1], [2]. Therefore, the United States Environmental Protection Agency (U.S. EPA) implemented the Integrated Atmospheric Deposition Network (IADN) program to monitor air pollution over the Great Lakes. ...
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The targeted compounds included Polychlorinated Biphenyls (PCBs), Pesticides (PESTs), Polycyclic Aromatic Hydrocarbons (PAHs) and so on in the Great Lakes Integrated Atmospheric Deposition Network (IADN), which is a platform based on the IoT (Internet of Things) technology to collect environmental pollutants data. While previous studies usually employed traditional statistical approaches to analyze the IADN results, we performed a complete modeling workflow of the total concentrations of PCBs, PESTs, and PAHs (which is referred to as $\sum $ PCBs, $\sum $ PEST s and $\sum $ PAHs orderly) in 1990–2016 samples by using a machine learning algorithm combined with data-driven research method, which lets the model fit the data, so as to change the model to achieve the effect. The main results of this article are as follows, 1) identifying the spatial and temporal trends of POPs (Persistent Organic Pollutants) in the air of the Great Lakes; 2) An appropriate data-driven intelligent model was constructed for the data at EH (Eagle Harbor) and STP(Sturgeon Point) sampling sites, via which we estimated their $\sum $ PCBs, $\sum $ PESTs, and $\sum $ PAHs in the following 4–5 years, showing the concentrations will continue declining with slight fluctuations; 3) The important role which IoT played in smart environmental protection was pointed out.
... Our WT sites still retain the natural WT variation in response to seasonal precipitation and evapotranspiration events that are common in northern peatlands. The lowered, raised, and intermediate sites are covered by a continuous moss mat of predominately Sphagnum angustifolium, S. capillifolium, and S. magellanicum and contain similar vegetation structure that is representative of a poor fen peatland in the Upper Great Lakes region [Crum and Planisek, 1988;Johnston et al., 2007]. Dominant tracheophyte species included the shrubs Chamaedaphne calyculata, Kalmia polifolia, Ledum groenlandicum, and Vaccinium oxycoccos; graminoids Carex oligosperma and Eriophorum vaginatum; and trees Larix laricina and Picea mariana [Hribljan, 2012]. ...
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Dissolved organic carbon (DOC) production, consumption, and quality displayed differences after long-term (~55 years) hydrological alterations in a poor fen peatland in northern Michigan. The construction of an earthen levee resulted in areas of a raised and lowered water table (WT) relative to an unaltered intermediate WT site. The lowered WT site had greater peat aeration and larger seasonal vertical WT fluctuations that likely elevated peat decomposition and subsidence with subsequent increases in bulk density, vertical hydraulic gradient, decreased hydraulic conductivity (Ksat), and a greater pore water residence time relative to the unaltered site. The raised WT site displayed a decreased Ksat combined with seasonal upwelling events that contributed to a longer residence time in comparison to the unaltered site. These differences are potentially contributing to elevated DOC concentrations at the lowered and raised WT site relative to the unaltered site. Additionally, spectrophotometric indices and chemical constituent assays indicated the lowered site DOC was more aromatic and contained elevated concentrations of phenolics compared to the intermediate site. The raised site DOC was less aromatic, more humified, and also had a greater phenolic content than the intermediate site. Furthermore, a microbial mineralization incubation showed DOC in the raised site contained the greatest labile carbon source. Based on our results, long-term WT alterations will likely impose significant effects on DOC dynamics in these peatlands; however, WT position alone was not a good predictor of DOC concentrations, though impoundment appears to produce a more labile DOC whereas drainage increases DOC aromaticity.
... The ISA must have higher values for the relative abundance and frequency in each category (Mc-Cune and Grace 2002), which was also satisfied in the case of our indicators. Practical, sensible indication of species for each zone or association linked with a particular set of environment can further be utilized for exploration of mines as well [67]. Unlike to our study, two species of Acacia viz.mangium and auriculiformis along with Cassia seamea and Dalbergia sissoo were found to be growing satisfactory in the Coal mine zones, India [68][69]. ...
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Introduction There has been limited research conducted on the identifications/methodological approaches of using plant species as indicators of the presence of economically, important mineral resources. Objectives This study set out to answer the following questions (1) Do specific plant species and species assemblages indicate the presence of mineral deposits? and (2) if yes, then what sort of ecological, experimental, and statistical procedures could be employed to identify such indicators? Methods Keeping in mind these questions, the vegetation of subtropical mineral mines sites in northern Pakistan were evaluated using Indicator Species Analysis (ISA), Canonical Correspondence Analysis (CCA) and Structural Equation Modeling (SEM). Results A total of 105 plant species belonging to 95 genera and 43 families were recorded from the three mining regions. CA and TWCA classified all the stations and plants into three major mining zones, corresponding to the presence of marble, coal, and chromite, based on Jaccard distance and Ward’s linkage methods. This comprehended the following indicator species: Ficus carica, Isodon rugosus and Ajuga parviflora (marble indicators); Olea ferruginea, Gymnosporia royleana and Dicliptera bupleuroides (coal indicators); and Acacia nilotica, Rhazya stricta and Aristida adscensionis (chromite indicators) based on calculated Indicator Values (IV). These indicators were reconfirmed by CCA and SEM analysis. Conclusion It was concluded that ISA is one of the best techniques for the identification/selection of plant indicator species, followed by reconfirmation via CCA and SEM analysis. In addition to establishing a robust approach to identifying plant indicator species, our results could have application in mineral prospecting and detection.
... Dabei haben verschiedene Arten verschiedene Toleranz- grenzen gegenüber einzelnen Schad-und Nähr- stoen, wobei genaue Kennzahlen selten bekannt sind ( Lenkenho & Rose, 2004). Da einzelne Arten innerhalb eines Biotops in Konkurrenz zueinan- der stehen, können sich schon durch geringfügige Zu-oder Abnahmen von Grundwasserinhaltsstof- fen Veränderungen der Biozönose ergeben (Seilheimer et al., 2009;Johnston et al., 2007;Lenkenho & Rose, 2004). Trotz dieser Komplexität las- sen sich ein paar generelle Prozesse aber absehen (s. ...
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Biodiversity and Climate Change - impact on the groundwater in Germany
... Trees are often scattered throughout the fen but are concentrated along the upland margin, and are often killed when Great Lakes water levels rise, especially in low areas and near the lake. (Above species lists were compiled from Voss 1972, 1985, Albert et al. 1989, Minc 1996, 1997a, 1997b, Minc and Albert 1998a, Albert 2001, 2003, Penskar et al. 2002, Johnston et al. 2007, Cohen 2009a, Cohen et al. 2009, NatureServe 2009, MNFI 2010 Plant species composition responds rapidly to changes in water levels. Among the species that appear in large numbers in coastal fens when the water level drops are butterwort, Kalm's St. John's-wort, low calamint, Kalm's lobelia, grass-of-Parnassus, Indian paintbrush, dwarf Canadian primrose, silverweed, and Houghton's goldenrod (Solidago houghtonii, federal/ state threatened) (Minc 1997b, Kost et al. 2007). ...
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Overview: Coastal fen is a sedge-and rush-dominated lacustrine wetland that occurs on calcareous substrates along Lake Huron and Lake Michigan north of the climatic tension zone. The community occurs on marl and organic soils in historic coastal embayments and on moderately alkaline, carbonate-rich fine-textured sands and clays lakeward. Vegetation is comprised primarily of calciphilic species capable of growing on wet alkaline substrates. Fluctuating Great Lakes water levels at multiple spatial and temporal scales and groundwater seepage are the primary natural processes that influence community structure, species composition, and succession.
... Plant species can also be used as indicators. Johnston et al. (2007) studied the relationship of plant species which were identified as indicators in the U.S Great Lakes coastal wetlands with their environmental preference in the habitat. According to Carrignan and Villard (2002), indicator species can be used for assessing ecosystem integrity. ...
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Sutomo, Darma IDP, Priyadi A, Iryadi R. 2018. Trees species diversity and indicator species in Bedugul forest ecosystem, Bali, Indonesia. Biodiversitas 19: 2213-2218. Bedugul area is an endorheic basin landscape with 3 lakes namely, Beratan, Buyan, Tamblingan, which is surrounded by Bukit Mangu, Tapak and Lesung. Topography of the area shows sloping to steep slopes with altitude on the lake surface ± 1,100 m asl and the highest peak of Bukit Mangu 2002 m asl. Ecological studies have not been optimal so identification of comprehensive ecological potential is carried out. Measurement of tree vegetation diversity was carried out by Centered Quarter Method and important value ratio analysis and location elevation class. The results of the inventory of tree species diversity in the Bedugul Bali forest area recorded 35 species and 13 indicator tree species. From the number of indicator tree species in the Mangu hill forest area there are 5 types of Ficus sp, Platea latifolia, Polyosma integrifolia, Lindera sp. and Syzygium sp., Bukit Tapak forest area consists of 4 species, Casuarina junghuhniana, Acronychia trifoliate, Astronia spectabilis and Homalanthus giganteus, the forest area of Bukit Lesung consists of 4 types of Lophopetalum javanicum, Syzygium racemosum, Dysoxylum nutans and Dendrocnide peltata.
... In addition to being among the least disturbed by human influences in all the Great Lakes Cvetkovic and Chow-Fraser 2011) and the most peat-dominated (Epstein et al. 1997;Minc and Albert 1998), they support among the highest levels of biodiversity (Brazner et al. 2000;Trebitz et al. 2009), including many rare species (Epstein et al. 1997) and some like wild rice (Zizania palustris) that used to be common but no longer are in most of the Great Lakes Basin (Meeker 1996). While much of the biodiversity characterization effort in Lake Superior coastal wetlands has focused on fish communities (e.g., Epstein et al. 1997;Brazner et al. 2001;Trebitz et al. 2011), stable isotope studies have provided insights about entire food webs (e.g., Keough et al. 1998;Sierszen et al. 2006Sierszen et al. , 2012a, and assemblages of birds (e.g., Howe et al. 2007), amphibians (e.g., Price et al. 2005), macroinvertebrates (Kang et al. 2007), vascular plants (e.g., Johnston et al. 2007), fish (e.g., Bhagat et al. 2007), and diatoms (Reavie 2007) have all been the focus of ecological indicator studies that included coastal wetlands in Lake Superior (also see Brazner et al. 2007;GLCWC 2008). The hydromorphic determinants of aquatic habitat variability (Trebitz et al. 2005), including nutrient availability and water quality (Morrice et al. 2009), that supports biodiversity in Lake Superior coastal wetlands have also been examined. ...
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There are more than two thousand coastal wetlands that encompass an area of about 215,000 ha in the Laurentian Great Lakes (LGL) of North America. Coastal wetlands in the LGL are distinguished hydrologically from nearby inland wetlands by a direct surface water connection with waters of an adjacent Great Lake. Daily, seasonal, annual and decadal lake level fluctuations exert important influences on the ecology of LGL coastal wetlands. Levels of human impacts in the LGL are generally greatest in the south, near the larger centers of population and most intense agriculture. Lake Superior is the largest (82,100 km2) and most northern of the LGL and coastal wetlands associated with Lake Superior are among the least disturbed by human influences. The distribution of coastal wetlands along the US shoreline of Lake Superior in Wisconsin and Michigan is skewed towards the southwestern end of the lake due to differential effects of isostatic adjustment following glaciation. The locations, geomorphic settings and basic characteristics of these south-shore wetlands are provided. Great Lakes coastal wetlands come in a variety of shapes and sizes. There is general agreement that there are three primary geomorphic types – lacustrine, riverine and barrier-protected with riverine and barrier-protected being most common along the US shoreline of Lake Superior. Coastal wetlands in Lake Superior are the most peat-dominated and support some of the highest levels of biodiversity among all LGL habitats. Process-oriented work indicates that Lake Superior coastal wetlands, 1) can export considerable numbers of young fish to adjacent bays and nearshore food webs, 2) have unique habitat fingerprints manifest in fish biochemical signatures that can be used to quantify wetland-nearshore interactions, and 3) structure, function, and response to anthropogenic stressors are all strongly influenced by hydrogeomorphic setting. Shoreline and watershed development, invasive species and climate change are among the most challenging factors affecting the integrity of Lake Superior and other Great Lakes coastal wetlands.
... While a small subset of metrics was common to all four IBIs (i.e., Nonnative species richness and % Richness of species particularly sensitive to environmental degradation), most metrics pertained uniquely to specific vegetation types. The identification of metrics that uniquely reflected the condition of different vegetation zones makes sense given that vegetation zonation in coastal wetlands is governed by broad-scale drivers such as hydrology (Keddy and Reznicek 1986;Lishawa et al. 2010), nutrient availability (Lougheed et al. 2001;Croft and Chow-Fraser 2007), wave exposure Johnston et al. 2007), and sediment characteristics . These drivers, along with physical habitat differences among the vegetation types themselves, all influence faunal community structure Uzarski et al. 2005;Cvetkovic et al. 2010). ...
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Biotic indicators are useful for assessing ecosystem health because the structure of resident communities generally reflects abiotic conditions integrated over time. We used fish data collected over 5 years for 470 Great Lakes coastal wetlands to develop multi-metric indices of biotic integrity (IBI). Sampling and IBI development were stratified by vegetation type within each wetland to account for differences in physical habitat. Metrics were evaluated against numerous indices of anthropogenic disturbance derived from water quality and surrounding land-cover variables. Separate datasets were used for IBI development and testing. IBIs were composed of 10–11 metrics for each of four vegetation types (bulrush, cattail, water lily, and submersed aquatic vegetation). Scores of all IBIs correlated well with disturbance indices using the development data, and the accuracy of our IBIs was validated using the testing data. Our fish IBIs can be used to prioritize wetland protection and restoration efforts across the Great Lakes basin. The IBIs will also be useful in monitoring programs mandated by the Agreement between Canada and the United States of America on Great Lakes Water Quality, such as for assessing Beneficial Use Impairments (BUIs) in Great Lakes Areas of Concern, and in other ecosystem management programs in Canada and the USA.
... In addition to being among the least disturbed by human influences in all the Great Lakes Cvetkovic and Chow-Fraser 2011) and the most peat-dominated (Epstein et al. 1997;Minc and Albert 1998), they support among the highest levels of biodiversity (Brazner et al. 2000;Trebitz et al. 2009), including many rare species (Epstein et al. 1997) and some like wild rice Zizania palustris that used to be common but no longer are in most of the Great Lakes Basin (Meeker 1996). While much of the biodiversity characterization effort in Lake Superior coastal wetlands has focused on fish communities (e.g., Epstein et al. 1997;Brazner et al. 2001;Trebitz et al. 2011), stable isotope studies have provided insights about entire food webs (e.g., Keough et al. 1998;Sierszen et al. 2006Sierszen et al. , 2012a, and assemblages of birds (e.g., Howe et al. 2007), amphibians (e.g., Price et al. 2005), macroinvertebrates (Kang et al. 2007), vascular plants (e.g., Johnston et al. 2007), fish (e.g., Bhagat et al. 2007), and diatoms (Reavie 2007) have all been the focus of ecological indicator studies that included coastal wetlands in Lake Superior (also see Brazner et al. 2007;GLCWC 2008). The hydromorphic determinants of aquatic habitat variability (Trebitz et al. 2005), including nutrient availability and water quality (Morrice et al. 2009), that supports biodiversity in Lake Superior coastal wetlands have also been examined. ...
Article
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Tussock formation is a global phenomenon that enhances microtopography and increases biodiversity by adding structure to ecological communities, but little is known about tussock development in relation to environmental factors. To further efforts to restore wetland microtopography and associated functions, we investigated Carex stricta tussock size in relation to elevation (a proxy for water depth) at a range of sites in southern Wisconsin, USA, and tested the effect of five hydroperiods and N+P addition (15 g N/m2 + 0.37 g P/m2) on tussock formation during a three-year mesocosm experiment. Wet meadows dominated by C. stricta averaged 4.9 tussocks/m2, with a mean volume of 1160 cm3 and height of 15 cm. Within sites, taller tussocks occurred at lower elevations, suggesting a structural adaptation to anoxic conditions. In our mesocosm experiment, C. stricta accelerated tussock formation when inundated, and it increased overall productivity with N + P addition. Within two growing seasons, continuous inundation (+18 cm) in the mesocosms led to tussocks that were nearly as tall as in our field survey (mean height in mesocosms, 10 +/- 1.3 cm; maximum, 17 cm). Plants grown with constant low water (-18 cm) only formed short mounds (mean height = 2 +/- 0.4 cm). After three growing seasons, the volume of the largest tussocks (3274 +/- 376 cm3, grown with +18 cm water depth and N + P addition) was 12 times that of the smallest (275 +/- 38 cm3, grown with -18 cm water depth and no N + P). Though tussock composition varied among hydroperiods, tussocks were predominantly organic (74-94% of dry mass) and composed of leaf bases (46-59%), fine roots (10-31%), and duff (5-13%). Only the plants subjected to high water levels produced the vertically oriented rhizomes and ascending shoot bases that were prevalent in field-collected tussocks. Under continuous or periodic inundation, tussocks achieved similar heights and accumulated similar levels of organic matter (range: 163-394 g C/m2), and we conclude that these hydroperiods can accelerate tussock formation. Thus, C. stricta has high utility for restoring wetland microtopography and associated functions, including carbon accumulation.
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Wetlands of the Great Lakes region are increasingly dominated by invasive cattails (Typha angustifolia andTypha Xglauca) which form dense stands of live and dead biomass that may reduce plant diversity. We hypothesized that differences in plant litter accumulation explain cattail dominance under certain hydrologic regimes related to wetland hydrogeologic setting. We investigated cattail abundance, litter accumulation, and species density in three bayside wetlands hydrologically connected and three protected wetlands hydrologically isolated from Lake Ontario. Mean litter biomass was higher in bayside wetlands (1.7–2.6 vs. 0.4–1.2 kg/m2) and negatively related to species density (p = 0.004) in both settings. A litter addition experiment demonstrated that fallen litter negatively influenced seedling survival (p = 0.061) and species density (p = 0.024). Decomposition rates accounted only partially for higher overall litter accumulation in bayside wetlands. Growing season water levels in bayside wetlands tracked Lake Ontario levels and showed less variation than protected wetlands. More stable water levels and higher density of standing dead stems in bayside wetlands may limit litter fragmentation, resulting in greater litter accumulation. Thus, anthropogenic and natural factors affecting cattail litter production, fragmentation, and decomposition could influence species diversity in coastal wetlands.
Chapter
It is often difficult to know what to measure when conducting a wetland assessment. There are a wide variety of variables to consider across the three main parameters—water, vegetation, and soils. To complicate things even further, the aspect of time and space must be considered if you wish to be able to make sense of your assessment. We present a discussion of water, vegetation, and soils and then give our best judgment of which variables to measure for each, and why some might be more useful than others. The merits and problems with gathering data from single visits versus multiple visits are discussed, as well as the level of expertise needed in some instances for certain variables to be useful. We do not discuss assessment and inventory methods as these will follow once you chose your assessment variables most relevant to your goals.
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The invasion and expansion of the non-native Phragmites australis in Great Lakes coastal wetlands is of increasing concern, but quantitative studies of the extent, rate, and causes of invasion have been lacking. Here we revisited 307 plots in 14 wetlands along the Great Lakes coast in 2005 that had previously been sampled for vegetation in 2001–2003. During the 2–4years between sample events, Phragmites occurred in 101 plots. Genetic analysis revealed that none of the Phragmites samples collected at the 14 wetlands belonged to the native genotype. Decreases in water depth and bare soil area were associated with the greatest increases in Phragmites cover. Phragmites invasion was greater on Lakes Michigan, Huron, and Erie than it was on Lake Ontario, and occurred predominantly on sandy substrates. Soil water concentrations of NO3-N, NH3-N, and soluble reactive P did not differ significantly between plots with and without Phragmites. Monitoring coastal wetlands where water level has dropped and controlling Phragmites at early stages of invasion are essential for maintaining healthy Great Lakes coastal wetlands of high species diversity and wildlife habitat. This becomes important as water levels in the Great Lakes have reached extreme lows and are expected to decline with future climate change. KeywordsExotic species-Invasion-Invasive species-Nutrients-Soil-Water level
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Carbon takes a variety of forms in beaver ponds and beaver meadows, including live plant biomass, standing dead biomass, soil organic matter, soil carbonates, dissolved organic carbon, and trace gases. The pools of carbon in these storage compartments and the fluxes between them are discussed. The slow decomposition rate of beaver meadow plant litter under anaerobic conditions promotes the accumulation of organic (O) soil horizons, which have a calculated mean residence time of 69 years. The carbon per unit area in soils that were formerly impounded by beavers (15.1 ± 6.8 km C m−2) was nearly twice that of adjacent never-impounded forest soils (8.2 ± 2.9 km C m−2). Beaver meadow sedge peat mineralization was compared with that of bog peat in long-term (80-week) laboratory incubations. Beaver meadow sedge peat had significantly higher carbon mineralization rates under all incubation conditions except aerobic incubation at 15 °C (other treatments were anaerobic incubation at 15 and 30 °C and aerobic incubation at 30 °C). Field measurement of trace gas fluxes showed that beaver ponds and beaver meadows with water table at or above the soil surface emitted methane, but beaver meadows with water tables below the soil surface did not.
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Chapter
Effectively sampling and analyzingwetland vegetation is an important part ofwetland science, as an indicator of wetland health and quality, and jurisdictional and mitigation success determinations. This chapter explains spatiotemporal vegetation sampling considerations by addressing key questions, such as which wetlands should be sampled and when and at what scale sampling should occur. It also plainly discusses the advantages and disadvantages of basic sampling techniques, such as different types of plot-based, plotless, and releve’ systems. Methods of assessing different vegetation and environmental attributes, such as cover and functional groups are discussed in detail. The chapter then describes methods of analyzing wetland vegetation, including simple summary analyses and more complex multivariate methods, such as classification, ordination, and floristic quality indices. Explanations of different types of these analyses and their advantages and disadvantages are provided. Finally, both field and laboratory-based exercises in sampling and analysis are provided for faculty and students studying wetland vegetation.
Book
Wetlands serve many important functions and provide numerous ecological services such as clean water, wildlife habitat, nutrient reduction, and flood control. Wetland science is a relatively young discipline but is a rapidly growing field due to an enhanced understanding of the importance of wetlands and the numerous laws and policies that have been developed to protect these areas. This growth is demonstrated by the creation and growth of the Society of Wetland Scientists which was formed in 1980 and now has a membership of 3,500 people. It is also illustrated by the existence of 2 journals (Wetlands and Wetlands Ecology and Management) devoted entirely to wetlands. To date there has been no practical, comprehensive techniques book centered on wetlands, and written for wetland researchers, students, and managers. This techniques book aims to fill that gap. It is designed to provide an overview of the various methods that have been used or developed by researchers and practitioners to study, monitor, manage, or create wetlands. Including many methods usually found only in the peer-reviewed or gray literature, this 3-volume set fills a major niche for all professionals dealing with wetlands.
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Ecological restoration typically aims to re‐establish dominant plant species and their native associates, despite the lack of guidance on which associates to introduce initially. Analysis of naturally occurring plant communities can provide criteria to shorten the list of species that are associated with dominants, in order to focus revegetation efforts on species likely to establish. Using the example of sedge meadows, we evaluated wetland vegetation data from Laurentian Great Lakes wetlands to identify “preferential associates,” that is, species that co‐occur more frequently than expected based on their overall abundance. A total of 176 taxa occurred within the two hundred and thirty‐nine 1 × 1 m2 plots in 48 wetlands that contained Carex stricta, a widespread tussock‐forming sedge. Of 58 species that co‐occurred with C. stricta where it was dominant (≥50% plot cover), we identified 26 associates using Bray–Curtis similarities and we determined that 12 of the 26 were preferential using an electivity index. The electivity index identified preferential associates even when they occurred infrequently or had low mean cover per plot. We provide guidance on how to initiate restoration with preferential associates.
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The evaluation index system of swamp degradation is one of the key scientific issues in the frontier field of international wetland science research. On the basis of long-term swamp field reconnaissance, and according to the fixed position ecological investigation of plant communities and the analysis of soil samples in 20 swamp plots in three belt transects of swamp degradation research under the stress of drainage in 2009, the swamps in the Zoige Plateau of Sichuan were classified into three groups with seven swamp communities, i. e., undisturbed (A type), disturbed by long-term and weak drainage (B-D type), and disturbed by short-term and strong drainage (E-G type), according to the species importance value and by Two-Way Indicator Species Analysis (TWINSPAN). The degradation degree of the swamps was graded by the method of Principal Components Analysis (PCA), and the swamp vegetation evaluation index (SVEI) and soil evaluation index (SSEI) were developed. Based on the SVEI, the swamps were classified as pristine swamp, lightly degraded swamp, moderately degraded swamp, and severely degraded swamp. Based on the SSEI, the swamps in Hongyuan County were divided into three grades, i. e. pristine swamp, lightly degraded swamp, and severely degraded swamp, while those in Ruoergai County were divided into lightly degraded swamp, moderately degraded swamp, and severely degraded swamp. The similarity of TWINSPAN classification results and SVEI/SSEI evaluation results was above 70%, indicating that both SVEI and SSEI were effective for the swamp degradation grading, and different classification methods should be combined to comprehensively evaluate the swamps in the Plateau.
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This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the 'sampled patch size,' i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and Satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
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The species-area curve has been used to link the biological with the geographical. Larger areas of land would seem to contain more species as a result of both the effect of sampling (i.e. more samples are taken to represent larger areas) and ecological processes (i.e. island biogeography theory and hypotheses relating to habitat diversity, successional development, species-energy, target-area, incidence function, small island habitat and disturbance). Unfortunately, the species-area curve is usually interpreted as though it was due entirely to ecological processes when it could be due largely to sampling. Modelled and real data (for forests in Ghana) demonstrated that while the effect of both ecological processes alone and sampling alone increased species number with area, only ecological processes could be expected to increase the number of species per unit area. These results suggest that before a species-area curve could be used as an indicator of ecological processes the effect of sampling on the species-area curve must first be removed.
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21 at Fond du Lac, 44 m gL 21 at Pokegama) Sedimentation rates vary among geomorphic land- that were orders of magnitude higher than elsewhere in the wetlands. forms in riverine wetlands (reviewed by Johnston et Summer denitrification potential was high in the levees (∪ 6n mol N 2O
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This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the "sampled patch size," i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
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Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for apopulation of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.
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Dominant species play key roles in shaping community structure, but their behavior is far from uniform. We speculated that recognition of different behaviors (determined objectively) would be an indicator of the condition of plant communities. We developed a species dominance index (SDI) to identify dominant species and compare their behavior across multiple spatial scales. The SDI is based on three attributes (mean cover, mean species suppression, and tendency toward high cover), and it identifies up to 38 dominants within 74 Great Lakes coastal wetlands. Dichotomizing each of the attributes in a 2 × 2 × 2 matrix produced seven dominant behaviors, or forms, all of which occurred in Great Lakes wetlands. Species sho wed different dominant forms among locations and aggregation scales. Showing predominantly “monotype” form, invasive Typha was the taxon that was most often dominant in the samples. By quantitatively measuring dominance and describing dominance form, SDI can add insight into community change and is a useful addition to indicators of community condition.
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Soils were examined at 35 locations and described in detail at 22 locations to determine the stratigraphy and distribution of materials in a lakeside wetland in Wisconsin. Histic and mineral soil samples were analyzed for organic P, inorganic P, ammonium, nitrate, and organic N. Particle size distributions were determined for the mineral soils. It was found that soils formed in the wetland are young, not well developed, and derived from a variety of parent materials: glacial till, glacio-fluvial deposits, lacustrine deposits, histic materials, colluvium, and alluvium. Major soils in the wetland include Borosaprists, Haplaquents and Fluvaquents. Phosphorus concentrations are highest in silt loam alluvium and histic deposits, and lowest in glacio-fluvial deposits, marl, and sandy alluvium.
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Despite the documented importance of hydrodynamics in influencing the structure and function of Great Lakes coastal wetlands, systematic assessments of coastal wetland hydrology are lacking. This paper addresses this gap by describing patterns in lake and tributary inputs, water residence times, and mixing regimes for a suite of western Lake Superior wetlands that differ in the amount of tributary and seiche flow they receive. We show that variability in tributary flows among wetlands and over time is far greater than variability in seiche-driven water movements, and that the amount of tributary flow strongly influences wetland hydrology via effects on water mixing and residence times, seiche size, mouth closures, and relative amounts of main and off-channel areas. Wetland seiche amplitudes were reduced in systems with small mouth openings and wetland mouth size was correlated with tributary flow. All wetlands experienced seiche-driven water level oscillations, but there was lake water intrusion only into those wetlands where tributary outflow was small relative to the seiche-driven inflow. Wetlands in settings exposed to long-shore sediment transport exhibited periodic mouth closures when stream flows were low. The absolute and relative size of lake and tributary inputs must be explicitly considered in addition to wetland morphology and landscape setting in studies seeking to understand determinants of coastal wetland structure, function, and response to anthropogenic stressors.
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Time series measurements of water transparency were made at stations located in the passages on either side of Chambers Island from May through October, 1989. These data were combined with the current measurements of Miller and Saylor (1993) to determine the sediment transport into and out of southern Green Bay. The data show that the sediment flux past Chambers Island is driven primarily by the non-tidal circulation in the two channels; both tidal and storm effects are of secondary importance. The cumulative sediment flux is southward through the western channel and northward in the eastern channel with a small net transport of sediment into the southern bay. Since the sediment load from tributaries to the bay is much greater than the transport in the channels, this excess sediment must be stored in the southern bay.
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Consecutive Landsat images of a red clay turbidity plume due to runoff from Nemadji River, Wisconsin, are used in computation of the horizontal eddy diffusivity for Lake Superior. Dispersion of turbid areas ranging from 2.5-5.4 km in diameter and having average velocities of 0.4 cm/sec-6.1 cm/sec are investigated. The coefficient for horizontal eddy diffusivity ranges from 0.6-1.5 m2/sec.
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Canonical Correspondence Analysis (CCA) is quickly becoming the most widely used gradient analysis technique in ecology. The CCA algorithm is based upon Correspondence Analysis (CA), an indirect gradient analysis (ordination) technique. CA and a related ordination technique, Detrended Correspondence Analysis, have been criticized for a number of reasons. To test whether CCA suffers from the same defects, I simulated data sets with properties that usually cause problems for DCA. Results indicate that CCA performs quite well with skewed species distributions, with quantitative noise in species abundance data, with samples taken from unusual sampling designs, with highly intercorrelated environmental variables, and with situations where not all of the factors determining species composition are known. CCA is immune to most of the problems of DCA.
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Tested whether diffuse competition is correlated with standing crop and organic-matter content in the soil of a lakeshore plant community. Diffuse competition was correlated significantly and positively with both of these factors. Standing crop was correlated positively with organic-matter content in the soil, suggesting that a general measure of habitat productivity may be indirectly related to the intensity of diffuse competition.-from Authors
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Coastal erosion/accretion rates measured from aerial photos taken in the 1930s and 1960s-1970s were compared with lithologic and geomorphic properties of the northern and southern coasts of western Lake Superior. The coasts were divided into four lithologic types based on Quaternary geology: bedrock, clay, sandy till, and water-laid sand and gravel. Average erosion of the southern coast was significantly higher than that of the northern coast for clay (0.78 vs. 0.14 m/yr), and for water-laid sand and gravel (1.89 vs. 0.16 m/yr). Sandy till on the southern coast eroded an average of 0.12 m/yr; till units were negligible along the northern coast. Bedrock constitutes 57% of the northern coast and has eroded at an average rate of 0.08 m/yr; bedrock exposures are rare along the southern coast. Clay coasts facing north or northwest eroded significantly faster than those facing south, and water-laid sand and gravel coasts facing north eroded significantly faster than those facing southeast. This is probably because major storm winds and waves come from the northeast, with a greater impact on the north- and northeast-facing shores. Offshore slope and bluff slope were not significantly related to erosion rates.
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Great Lakes coastal wetlands are subject to water level fluctuations that promote the maintenance of coastal wetlands. Point au Sauble, a Green Bay coastal wetland, was an open water lagoon as of 1999, but became entirely vegetated as Lake Michigan experienced a prolonged period of below-average water levels. Repeat visits in 2001 and 2004 documented a dramatic change in emergent wetland vegetation communities. In 2001 non-native Phragmites and Typha were present but their cover was sparse; in 2004 half of the transect was covered by a 3 m tall, invasive Phragmites and non-native Typha community. Percent similarity between plant species present in 2001 versus 2004 was approximately 19% (Jaccard's coefficient), indicating dramatic changes in species composition that took place in only 3 years. The height of the dominant herbaceous plants and coverage by invasive species were significantly higher in 2004 than they were in 2001. However, floristic quality index and coefficient of conservatism were greater in 2004 than 2001. Cover by plant litter did not differ between 2001 and 2004. The prolonged period of below-average water levels between 1999 and early 2004 exposed unvegetated lagoon bottoms as mud flats, which provided substrate for new plant colonization and created conditions conducive to colonization by invasive taxa. PCR/RFLP analysis revealed that Phragmites from Point au Sauble belongs to the more aggressive, introduced genotype. It displaces native vegetation and is tolerant of a wide range of water depth. Therefore it may disrupt the natural cycles of vegetation replacement that occur under native plant communities in healthy Great Lakes coastal wetlands.
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Invertebrate communities from different coastal marsh-plant communities were compared along wave-exposure gradients using data from 1994, 1998 and 1999. Data were subjected to correspondence analyses to search for patterns in invertebrate communities in relation to plant-community structure and wave exposure. In 1994, quantitative plant- and sediment-invertebrate samples were taken from nine habitats: four from inland, subsurface-connected marshes and five from littoral, emergent marshes. In 1998, sweep-net samples were taken from 13 plant communities: six on the exposed and seven on the protected side of an island. In 1999, 2–3 plant communities/sites were sampled with sweep nets from four sites around the Bay so that intersite differences between inner, less-exposed and outer, more-exposed habitats could be examined. In all three studies, correspondence analyses separated inland, protected or inner sites from littoral, exposed or outer sites, suggesting differences in invertebrate-community structure. For example, Hydracarina and Asellidae occurred in large numbers in inland sites, but were less common or absent from exposed, littoral sites. Littoral marshes also separated along an exposure gradient with Tanytarsini and Orthocladiinae collectors of organic particles occurring in very high numbers in outer, exposed areas where organic particles from the pelagic zone entered the marsh. Certain plant-community types clustered together (e.g. wet meadow and Scirpus) while others, such as Typha, stands clustered according to exposure to waves suggesting the importance of both plant-community structure and wave exposure in determining invertebrate-community structure. We present a conceptual model that suggests that invertebrates in Great Lakes' marshes are distributed along gradients of decreased mixing of pelagic water and increases in sediment organic matter from outer to inner marsh and between littoral and adjacent inland marshes. Some invertebrates do best on one end of these gradients, while the majority are generalists found across habitat types.
Article
We evaluated variability in cover estimation data obtained by (1) two sampling teams who double sampled plots and (2) one team that used two methods (line intercepts and visual estimation of cover classes) to characterize vegetation of herbaceous wetlands. Species richness and cover estimates were similar among teams and among methods, but one sampling team scored cover higher than the other. The line intercept technique yielded higher cover estimates but lower species richness estimates than the cover class method. Cluster analyses of plots revealed that 36% and 11% of plots sampled consecutively by two teams or using two methods, respectively, were similar enough in species composition and abundance to be paired together in the resulting clustering tree. Simplifying cover estimate data to presence/absence increased the similarity among both teams and methods at the plot scale. Teams were very similar in their overall characterization of sites when cover estimation data were used, as assessed by cluster analysis, but methods agreed best on their overall characterization of sites when only presence/absence data were considered. Differences in abundance estimates as well as pseudoturnover contribute to variability. For double sampled plots, pseudoturnover was 19.1%, but 57.7% of pseudo-turnover cases involved taxa with ≤ 0.5% cover while only 3.4% involved taxa with > 8% cover. We suggest that vegetation scientists incorporate quality control, calibrate observers and publish their results.
Article
Reference wetlands play an important role in efforts to protect wetlands and assess wetland condition. Because wetland vegetation integrates the influence of many ecological factors, a useful reference system would identify natural vegetation types and include models relating vegetation to important regional geomorphic, hydrologic, and geochemical properties. Across the U.S. Atlantic Coastal Plain, depression wetlands are a major hydrogeomorphic class with diverse characteristics. For 57 functional depression wetlands in the Upper Coastal Plain of South Carolina, we characterized the principal vegetation types and used a landscape framework to assess how local (wetland-level) factors and regional landscape settings potentially influence vegetation composition and dynamics. Wetland sites were stratified across three Upper Coastal Plain landscape settings that differ in soils, surface geology, topography, and land use. We sampled plant composition, measured relevant local variables, and analyzed historical transitions in vegetative cover types. Cluster analysis identified six vegetation types, ranging from open-water ponds and emergent marshes to closed forests. Significant vegetation-environment relationships suggested environmental “templates” for plant community development. Of all local factors examined, wetland hydrologic regime was most strongly correlated with vegetation type, but depression size, soil textural type, and disturbance history were also significant. Because hydrogeologic settings influence wetland features, local factors important to vegetation were partly predictable from landscape setting, and thus wetland types were distributed non-randomly across landscape settings. Analysis of long-term vegetation change indicated relative stability in some wetlands and succession in others. We developed a landscape-contingent model for vegetation dynamics, with hydroperiod and fire as major driving variables. The wetland classification, environmental templates, and dynamics model provide a reference framework to guide conservation priorities and suggest possible outcomes of restoration or management. Key WordsCarolina bay-depressional wetlands-environmental gradients-hydrogeologic setting-hydroperiod-landscape-reference wetlands-wetland management-restoration-vegetation types
Article
The Floristic Quality Index (FQI) has been proposed as a tool that can be used to identify areas of high conservation value, monitor sites over time, assess the anthropogenic impacts affecting an area, and measure the ecological condition of an area. FQI is based on the Coefficient of Conservatism (C), which is a numerical score assigned to each plant species in a local flora, primarily from best professional judgment, that reflects the likelihood that a species is found in natural habitats. FQI is computed by multiplying the mean Coefficient of Conservatism (C) by the square root of species richness for an observational unit. Great Lakes coastal wetlands were used to assess the properties and performance of various species richness, Coefficient of Conservatism, and Floristic Quality indices, as well as compare C-value assignments from two U.S. states (Wisconsin and Michigan). FQI and species richness increased with sampling area according to a power function, but C more or less remained constant. Sampling schemes should therefore focus on controlling sampling area and minimally sampling each community type at a site. In some cases, Wisconsin and Michigan assigned different values of C to the same species, highlighting possible effects due to the somewhat subjective nature of C-value assignment. Coefficient of Conservatism and Floristic Quality indices were better at discriminating differences between sites, independent of a condition gradient, than species richness alone, but neither index type outperformed the other. Both types of indices were also found to be acceptable ecological indicators of condition, although Floristic Quality indices consistently outperformed Coefficient of Conservatism indices in this capacity. Regardless of the subjectivity involved with the assignment of C-values and that ‘floristic quality’ is a human concept and not a true ecosystem property, both Coefficient of Conservatism and Floristic Quality indices seem to be effective indicators of condition in Great Lakes coastal wetland
Article
Sedimentation rate and nutrient concentrations were assessed in 1989 at four sites of differing stream morphometry in the Kakagon Sloughs, a Lake Superior coastal wetland in northern Wisconsin dominated by northern wild-rice (Zizania palustris). Pre-weighed sediment traps were placed at each site along deep-to-shallow water zones. Accrued sediment was collected during five time periods corresponding to differing stages of growth in wild-rice stands. There were higher sedimentation rates at the river sites (straight sections and inside and outside curves) when compared to the backwater site. Differences were also observed among depths and at the different time periods, demonstrating the influence of vegetation on the sedimentation process in this wetland complex. Higher sedimentation rates took place closest to the vegetation-open water interface (deep zones). However, in shallow zones, a significant proportion of the annual sedimentation took place during the submersed and floating leaf stages, showing the importance of these time periods for providing an annual input of sediment to large areas of riverine habitat. Of nutrients tested, both TKN and NO3-N had lower concentrations in the period following wild-rice stem elongation. These data suggest that the early growth habit of wild-rice (submersed and floating stages) promotes pulses of nutrient-rich sediment, which are necessary for the later nutrient-demanding stages of stem elongation and grain formation.
Article
Coastal wetlands of Lake Erie fall into three categories, depending on the type of protection available to the wetland vegetation: (1) coastal lagoons behind barrier beaches, (2) managed marshes protected by earthern and rip-rap dikes, and (3) estuarine tributary mouths. At one time the most important protection was that afforded by barrier bars or other natural shoreline features which formed quiet lagoons and embayments. Very few natural wetlands of this type still exist in Lake Erie. Most of the lagoon-type coastal marshes, if they have not been drained or filled or engulfed by the lake, have been replaced by the second type: managed-waterfowl marshes which are now protected by earthen rip-rap dikes. The third type of protection is the natural isolation from lake storms provided by the estuaries of virtually all of the tributaries entering Lake Erie, particularly at the western end. Large wetlands have developed along most of the estuaries where disturbance has been minimal. Estuarine coastal marshes currently form the majority of the naturally protected wetlands bordering western Lake Erie.
Article
In the United States, wetlands are often created (as compared with restored) as mitigation for damage done to natural wetlands by development or other activities. There is increasing concern that these created sites do not function as do natural wetlands, even after a period of years. Monitoring of these created wetlands often consists of an assessment of the percent herbaceous plant cover as some indicator of the functional success of the wetland. However, it is not at all clear that assessment of herbaceous cover translates into an accurate indicator of wetland function. In this paper I review several functions commonly ascribed to wetlands and assess the reported relationship of percent herbaceous cover to those functions (if any). Of six functions reviewed, only one has a probable (though indirect) positive relationship with the percent herbaceous plant cover on a site. More useful assessments of wetland function might be made with other structural indicators, such as basin morphometry, tree density, or basal area.
Article
Developing effective indicators of ecological condition requires calibration to determine the geographic range and ecosystem type appropriate for each indicator. Here, we demonstrate an approach for evaluating the relative influence of geography, geomorphology and human disturbance on patterns of variation in biotic indicators derived from multiple assemblages for ecosystems that span broad spatial scales. To accomplish this, we collected abundance information on six biotic assemblages (birds, fish, amphibians, aquatic macroinvertebrates, wetland vegetation, and diatoms) from over 450 locations along U.S. shorelines throughout each of the Great Lakes during 2002–2004. Sixty-six candidate taxon- and function-based indicators analyzed using hierarchical variance partitioning revealed that geographic (lake) rather than geomorphic factors (wetland type) had the greatest influence on the proportion of variance explained across all indicators, and that a significant portion of the variance was also related to response to human disturbance. Wetland vegetation, fish and bird indicators were the most, and macroinvertebrates the least, responsive to human disturbance. Proportion of rock bass, Carex lasiocarpa, and stephanodiscoid diatoms, as well as the presence of spring peepers and the number of insectivorous birds were among the indicators that responded most strongly to a human disturbance index, suggesting they have good potential as indicators of Great Lakes coastal wetland condition. Ecoprovince, wetland type, and indicator type (taxa vs function based) explained relatively little variance. Variance patterns for macroinvertebrates and birds were least concordant with those of other assemblages, while diatoms and amphibians, and fish and wetland vegetation were the most concordant assemblage pairs. Our results strongly suggest it will not be possible to develop effective indicators of Great Lakes coastal wetland condition without accounting for differences among lakes and their important interactions. This is one of the first attempts to show how ecological indicators of human disturbance vary over a broad spatial scale in wetlands.