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A unifying approach for evaluating the condition of wetland plant communities and identifying related stressors

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A unifying approach for evaluating the condition of wetland plant communities and identifying related stressors

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Abstract

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.

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... En el caso del estado ecológico de los humedales de ambientes semiáridos, es evidente que indicadores basados en las características fisico-químicas o bióticas de la lámina de agua no serían de gran utilidad de manera generalizada. Por el contrario, la vegetación puede reflejar bien las condiciones ambientales de estos sistemas Caçador et al, 2013) así como el efecto de posibles perturbaciones (Cronk and Fennessy, 2001;Mitsch and Gosselink, 2007), razón por la que se han desarrollado algunos indicadores de este tipo (véase por ejemplo Miller et al 2006;Johnston et al 2009). No obstante, no se cuenta con indicadores semejantes para el caso de humedales salinos de ambientes mediterráneos. ...
... A lo anterior se une la dificultad de discriminar la vegetación de los humedales a nivel de especie, dado que su identificación puede ser complicada o conllevar mucho tiempo, lo que puede conducir a errores taxonómicos o a costes desproporcionados. En este sentido, las comunidades vegetales contienen más información ecológica que las especies aisladas y son más fáciles de cartografiar utilizando sensores remotos (O'Connell, 2003;Johnston et al, 2009), lo cual puede ser una vía para solventar esta dificultad y así definir el estado ecológico de los humedales utilizando indicadores basados en las comunidades vegetales en lugar de taxones individuales. ...
... Although several indices based on plant species and communities have previously been used as a tool for wetland condition assessment in the U.S.A. (Johnston et al, 2009;López and Fennessy, 2002;Miller et al, 2006), such indices are lacking for semiarid Mediterranean saline wetlands and are needed in order to fulfill the European Water Framework. In the context of a proposal for monitoring semiarid Mediterranean saline wetlands, the main aim of this study was to investigate plant taxa as an ecosystem attribute that reflects long-term changes in wetland hydrological conditions. ...
... This analysis utilized three datasets that we and others collected for the Great Lakes Environmental Indicators project (USEPA, 2006) (1) a vegetation dataset collected at 90 coastal wetlands by botanists (Johnston et al., 2009b), (2) a water chemistry dataset collected at 100 coastal wetlands by scientists studying fish and diatoms (Reavie et al., 2006;Trebitz et al., 2007;Morrice et al., 2008), and (3) GIS-derived data summarized for the entire U.S. Great Lakes basin (Danz et al., 2007;Johnston et al., 2009a). We added no new data, but performed new statistical analyses to link the vegetation data with the water chemistry data at the 48 sites that were visited in common by the two field groups. ...
... The forty-eight wetlands ("sites") in which both vegetation data and water chemistry data were collected are well-distributed across the region (Fig. 1). Sampling details are provided by the parent studies (Reavie et al., 2006;Danz et al., 2007;Trebitz et al., 2007;Morrice et al., 2008;Johnston et al., 2009b), but are summarized below. ...
... Twenty-four environmental variables derived from existing geospatial data sources were summarized for each site, all computed for our prior publications (see Table 1 in Johnston et al., 2009b). These included several integrated measures of watershed anthropogenic stress, derived by principal components analysis of multiple stressors of a common anthropogenic origin (Danz et al., 2007): agriculture (PC1 AG), human population and development (PC1 URB), atmospheric deposition (PC1 ATDEP), point source pollution (PC1 NPDES), and the cumulative stress index (CSI), which was a generalized stress gradient derived from the preceding four principal components and land cover. ...
Article
U.S. coastal wetlands of the Laurentian Great Lakes span a north-to-south gradient (latitude 47–41° N) of increasing human population and agricultural intensity that alters their water chemistry and vegetation. We related field-measured water chemistry to vegetation condition and composition using data from 48 freshwater coastal wetlands along this sub-continental gradient, building upon previous findings that GIS-derived landscape descriptors could adequately predict vegetation condition in Great Lakes coastal wetlands. Our aim was to determine (1) whether plant communities could be differentiated by their surface water chemistry, and (2) if water chemistry could better predict wetland vegetation condition than GIS-derived variables. Seven distinct plant communities were identified by agglomerative hierarchical clustering and non-metric multidimensional scaling of vegetation cover data: Sphagnum-carpeted poor fens, Sparganium eurycarpum marshes, Calamagrostis canadensis wetlands, Schoenoplectus pungens marshes, Phragmites australis marshes, and two floristically distinct Typha-dominated marshes. There were significant differences (ANOVA) among the seven plant assemblages identified for most water chemistry metrics (Cl−, chlorophyll a, conductivity, NO3-N, pH, total N, total P, total suspended solids), but dissolved oxygen, dissolved organic carbon, and NH4-N did not vary significantly across the assemblages. The two different Typha-dominated plant communities were chemically distinct from each other in chlorophyll a, conductivity, NO3-N, pH and total suspended solids concentrations, and we recommend that they be separated into distinct associations: Typha spp. – Thelypteris palustris – Hydrocharis morsus-ranae and Typha spp. – C. canadensis – Leersia oryzoides. Plant communities tended to be geographically clustered, but wetlands that were geographic outliers of their floristic type were chemically similar to other wetlands in their plant community grouping despite being on different lakes. When offered both GIS-derived and field-measured potential predictor variables, a regression tree model of wetland condition chose only GIS-derived variables. However, a classification tree model derived solely from field-measured water chemistry variables correctly classified 79% of the sites into four plant community groupings based on total N, conductivity, and pH. Grouping wetlands by plant communities could provide a scientifically-defensible basis for stricter water quality standards to protect sensitive wetland types.
... Cumulative loss of coastal wetlands has been significant, although the region contains both large areas of relatively undisturbed wetlands as well as highly disturbed and managed wetlands (Smith et al., 1991). Therefore, protection, documentation, and understanding of the biological resources present in coastal wetlands of the Laurentian Great Lakes have been a common goal for decades Herdendorf, 1990;Johnston et al., 2009;Minc, 1997a;Smith et al., 1991). Studying the vegetation of coastal wetlands along the shorelines of the Laurentian Great Lakes is crucial to understanding both the natural diversity and the impacts of anthropogenic stressors on these wetlands (Herdendorf et al., 1981;Johnston et al., 2009;Johnston and Brown, 2013;Minc, 1997a;Stuckey, 1975). ...
... Therefore, protection, documentation, and understanding of the biological resources present in coastal wetlands of the Laurentian Great Lakes have been a common goal for decades Herdendorf, 1990;Johnston et al., 2009;Minc, 1997a;Smith et al., 1991). Studying the vegetation of coastal wetlands along the shorelines of the Laurentian Great Lakes is crucial to understanding both the natural diversity and the impacts of anthropogenic stressors on these wetlands (Herdendorf et al., 1981;Johnston et al., 2009;Johnston and Brown, 2013;Minc, 1997a;Stuckey, 1975). ...
... and Phragmites australis (Frieswyk and Zedler, 2007;Hudon, 1997;Tulbure et al., 2007). More recently, Johnston et al. (2009) used cluster analysis and non-metric multidimensional scaling to categorize and evaluate distributions of vegetation communities along environmental gradients. Our study expands upon their work by increasing the detail of the vegetation species composition and characterization as well as identifying community types in both meadow and emergent zones of observed wetland sites. ...
Article
Between 2011 and 2013, more than 300 coastal wetland sites were surveyed throughout the Laurentian Great Lakes as part of a coastal wetland monitoring project. Twenty-one wetland vegetation communities were identified through cluster analysis and indicator species analysis. Non-metric multidimensional scaling was used to ordinate sites based on species composition, and measured and calculated environmental parameters were used to evaluate environmental correlation with groups of sites (vegetation communities). Latitude, agricultural intensity, substrate, geomorphology, and water depth were found to account for the majority of the three-axis solution in the non-metric multidimensional scaling. Comparison with earlier studies indicates major increases in extent for several community types dominated by the common invasive species Phragmites australis, Typha angustifolia and T. × glauca. These invasive plants often formed similar species assemblages in both the meadow and emergent zones. Similarities in species composition between meadow and emergent communities indicate that species assemblages may be responding to fluctuations in water levels. This paper presents a unique classification of Great Lakes coastal wetlands with greater geographic range and increased detail in the meadow and emergent zones based on vegetation species composition. The classification is useful as a comparison to past and future ecological and restoration studies.
... Agricultural disturbance has been shown to be a major determinant of wetland plant communities (Johnston et al. 2009). The vegetation is related to soil nematode community composition, and less diversified vegetation implies less rich nematodes (Kardol et al. 2005). ...
... The plants at the edge of the wetland appear to grow higher and denser but are not richer in species than the central part of the wetland, possibly due to fertilizer and pesticide from the crop fields coming from runoff or wind. Agricultural disturbance has been shown to result mainly in reduced plant species richness and cover in wetlands embedded in the cropland landscape (Johnston et al. 2009;O'Connell et al. 2012). ...
Article
Full-text available
Cultivation for agricultural production often poses threats to nearby wetlands ecosystems in fertile landscapes. In this study, nematode ecological indexes were assessed through the main soil properties of the wetlands, farmlands, and edges of wetlands and farmlands in Jinchuan Wetland by the random sampling. Behavior and reproduction in Caenorhabditis elegans (C. elegans) exposed to the sampled waters were also examined. Stress proteins Hsp70 and Hsp90 were measured both in the living field samples of C. elegans and the lab-tested C. elegans. Our results suggested that disturbance to wetland ecosystems by nitrogen and phosphorus reduced nematode richness and proportions of bacterivore nematodes. Bacterivore nematode diversity and plant-parasitic ecological index were proven to be sensitive indicators of the ecological health of wetlands. Nematode Hsp70 were useful biosensors to monitor and assess the levels of nitrogen and phosphorus pollutions in wetlands. Furthermore, multi-level soil faunal assessments by canonical correspondence analysis showed that Jinchuan Wetland is threatened with non-point source pollution from nearby farmlands.
... Despite their importance, Great Lakes coastal wetlands (GLCWs) face many challenges from anthro-pogenic activities, as over 50% of GLCW area has been lost to filling, dredging, and diking, and remaining wetlands continue to be at risk of degradation (Maynard and Wilcox, 1997). Anthropogenic activities have been associated with increased concentrations of contaminants and altered water chemistry (Danz et al., 2007;Morrice et al., 2008;Robertson and Saad, 2011), along with changes in fish (Danz et al., 2007;Schock et al., 2014), macroinvertebrate (Schock et al., 2014), bird (Danz et al., 2007), and macrophyte communities (Johnston et al., 2009;Lougheed et al., 2001). ...
... For example, invasive cattail (Typha spp.) in GLCWs can alter light penetration, water chemistry, and nutrient cycling (Lishawa et al., 2014), which may impact phytoplankton. GLCWs also differ in surrounding land use (Johnston et al., 2009;Keough et al., 1999;Schock et al., 2014), which can influence phytoplankton biomass by altering physiochemical conditions within a wetland, including water nutrient concentrations (Cooper et al., 2016). ...
... Despite their importance, Great Lakes coastal wetlands (GLCWs) face many challenges from anthro-pogenic activities, as over 50% of GLCW area has been lost to filling, dredging, and diking, and remaining wetlands continue to be at risk of degradation (Maynard and Wilcox, 1997). Anthropogenic activities have been associated with increased concentrations of contaminants and altered water chemistry (Danz et al., 2007;Morrice et al., 2008;Robertson and Saad, 2011), along with changes in fish (Danz et al., 2007;Schock et al., 2014), macroinvertebrate (Schock et al., 2014), bird (Danz et al., 2007), and macrophyte communities (Johnston et al., 2009;Lougheed et al., 2001). ...
... For example, invasive cattail (Typha spp.) in GLCWs can alter light penetration, water chemistry, and nutrient cycling (Lishawa et al., 2014), which may impact phytoplankton. GLCWs also differ in surrounding land use (Johnston et al., 2009;Keough et al., 1999;Schock et al., 2014), which can influence phytoplankton biomass by altering physiochemical conditions within a wetland, including water nutrient concentrations (Cooper et al., 2016). ...
Article
Coastal wetlands of the Laurentian Great Lakes are diverse and productive ecosystems that provide many ecosystem services, but are threatened by anthropogenic factors, including nutrient input, land-use change, invasive species, and climate change. In this study, we examined one component of wetland ecosystem structure – phytoplankton biomass – using the proxy metric of water column chlorophyll-a measured in 514 coastal wetlands across all five Great Lakes as part of the Great Lakes Coastal Wetland Monitoring Program. Mean chlorophyll-a concentrations increased from north-to-south from Lake Superior to Lake Erie, but concentrations varied among sites within lakes. To predict chlorophyll-a concentrations, we developed two random forest models for each lake – one using variables that may directly relate to phytoplankton biomass (“proximate” variables; e.g., dissolved nutrients, temperature, pH) and another using variables with potentially indirect effects on phytoplankton growth (“distal” variables; e.g., land use, fetch). Proximate and distal variable models explained 16–43% and 19–48% of variation in chlorophyll-a, respectively, with models developed for lakes Erie and Michigan having the highest amount of explanatory power and models developed for lakes Ontario, Superior, and Huron having the lowest. Land-use variables were important distal predictors of chlorophyll-a concentrations across all lakes. We found multiple proximate predictors of chlorophyll-a, but there was little consistency among lakes, suggesting that, while chlorophyll-a may be broadly influenced by distal factors such as land use, individual lakes and wetlands have unique characteristics that affect chlorophyll-a concentrations. Our results highlight the importance of responsible land-use planning and watershed-level management for protecting coastal wetlands.
... Although several indices based on plant species and communities have previously been used as a tool for wetland condition assessment in the USA (Johnston et al., 2009;López and Fennessy, 2002;Miller et al., 2006), such indices are lacking for semiarid Mediterranean saline wetlands and are needed in order to fulfill the European Water Framework. In the context of a proposal for monitoring semiarid Mediterranean saline wetlands, the main aim of this study was to investigate plant taxa as an ecosystem attribute that reflects long-term changes in wetland hydrological conditions. ...
Article
Full-text available
During last decades semiarid Mediterranean saline wetlands have undergone several hydrological and biological changes as a consequence of increased water inputs from agricultural areas. Specific indices are needed in order to assess the condition of these unique ecosystems in relation to major hydrological disturbances at watershed level. Through the long-term study of selected plant taxa in a set of representative wetlands in Murcia province (SE Spain), together with the characterization of their watershed agricultural land uses, plant indicators of wetland condition were sought and then combined into a wetland condition index. Percentages of land cover classes of interest were weighted taking into account land cover arrangement and receiving wetland size. Characteristic perennial plant taxa were sampled in 1989 and 2008 and significant taxa frequency changes at each wetland site were determined. Regression analysis was used to relate wetland plant taxa frequency and watershed condition during the study period. Limonium spp., Arthrocnemum glaucum, Phragmites australis, Tamarix canariensis and Atriplex halimus showed significant relationships with watershed condition. Indicator taxa were thus identified and their frequencies were combined into an integrated index of wetland condition, which showed a robust relationship with watershed hydrological condition.
... While native upland species are assigned higher C values than non-native upland species, species endemic to wetland habitats are given the highest C values, making this a useful classification attribute for assessing wetland plant diversity [25,26]. FQAI is a widely used diversity metric in studies of wetland plant communities [27][28][29], as its emphasis on "quality" of plant species makes it a useful indicator of the desirability of plant species composition in wetland ecosystems [30]. We calculated FQAI scores for quadrats following the methods of Ohio EPA [19], which define FQAI as: ...
Conference Paper
Background/Question/Methods Understanding the effects of management practices on shifting relationships between structure and function over the course of ecosystem development should be a central goal of ecosystem restoration. Yet many of these relationships, such as those between plant biodiversity, spatial pattern of vegetation and community metabolism, remain poorly understood. In a decade-long experiment, we investigated the impact of different initial planting treatments and of nutrient enrichment on relationships among plant biodiversity, plant spatial pattern, and ecosystem function in restored wetland ecosystems. In 2003, six identical and hydrologically-isolated 0.18 ha experimental wetland “cells” were constructed in marginal farmland in northeast Ohio. Cells were subjected to one of three initial planting and management treatments, which were later simplified into two treatment groups. In 2010 and 2011, nitrogen and phosphorus fertilizers were applied to one cell from each of the three treatments to simulate agricultural run-off. Changes and differences in ecosystem function were assessed by measuring aquatic community metabolism, aboveground biomass, soil organic matter, and nutrient concentrations. Structure was characterized through annual plant biodiversity inventories and aerial photographs of plant cover that were analyzed to quantify vegetation spatial patterns. Results/Conclusions We found significant relationships among plant biodiversity, plant spatial pattern, and planting treatments. We observed significant and sustained differences in plant biodiversity, resulting from both planting treatment and habitat attributes of cells. Relationships between ecosystem function and both biodiversity and spatial pattern were more ambiguous. We found no direct relationships between biodiversity or spatial metrics and any measures of ecosystem function. These findings support the importance of initial wetland structure in achieving plant biodiversity in restored wetlands, but provide little additional evidence that species diversity has a major effect on nutrient retention, primary productivity, or soil organic matter in restored wetland systems. Over multiple years, biodiversity metrics correlated positively with spatial metrics, including mean patch shape complexity and contagion. This suggests that restored wetland landscapes comprised of patches with complex shapes (high edge-to-area ratios) that are highly clumped are home to a more diverse array of plant species. Links between biodiversity and spatial pattern suggest that aerial imagery may provide wetland managers with a robust tool for assessing plant biodiversity.
... There has been an increasing emphasis on using ecological-trait analyses to determine which stressors are influencing the functioning of aquatic communities (Schäfer et al. 2011). Multi-taxa responses to human stressors (Johnston et al. 2008;Johnston et al. 2009) are required to assess the likely functional consequences of species loss. Future research may also reveal functional genes associated with suites of taxa, and thus directly assess ecosystem-functional consequences using molecular analysis of biomonitoring data. ...
Article
Full-text available
Aquatic ecosystems are under threat from multiple stressors, which vary in distribution and intensity across temporal and spatial scales. Monitoring and assessment of these ecosystems have historically focussed on collection of physical and chemical information and increasingly include associated observations on biological condition. However, ecosystem assessment is often lacking because the scale and quality of biological observations frequently fail to match those available from physical and chemical measurements. The advent of high-performance computing, coupled with new earth observation platforms, has accelerated the adoption of molecular and remote sensing tools in ecosystem assessment. To assess how emerging science and tools can be applied to study multiple stressors on a large (ecosystem) scale and to facilitate greater integration of approaches among different scientific disciplines, a workshop was held on 10–12 September 2014 at the Sydney Institute of Marine Sciences, Australia. Here we introduce a conceptual framework for assessing multiple stressors across ecosystems using emerging sources of big data and critique a range of available big-data types that could support models for multiple stressors. We define big data as any set or series of data, which is either so large or complex, it becomes difficult to analyse using traditional data analysis methods.
... While intensive assessments are important for calibration and provide the most complete look at wetland condition, they are, by definition, time consuming and may require specialized knowledge to deploy, thus limiting their utility for routine activities of statewide programs (Fennessy et al., 2007). Increasingly, states are favoring the use of rapid assessment methods that provide a similar level of sensitivity, yet require less of a commitment in time and resources (Fennessy et al., 2007; Johnston et al., 2009; Stein et al., 2009). ...
Article
Floristic Quality Assessment is a proven technique for evaluating the condition of a variety of habitats including wetlands. Its utility in state monitoring and assessment programs, however, has been curtailed by the additional effort and expertise needed for deployment. In this study, we tested the validity of two prerequisites of floristic quality assessment: the need for a comprehensive species list and the requirement that all taxa be identified to species. The mean coefficient of conservatism (mean C) was shown to be the most sensitive variable of the index and was used to test its efficacy in a rapid context. Mean C demonstrated a lack of significant response when graminoid taxa were selectively removed and also when scores were calculated based on dominant taxa only (C¯dom). The muted response observed is likely due to redundancy in the species list (many plants with the same C value) and the averaging of C values. Site ranks did shift when based on C¯dom, however, and this result may have implications on how individual sites are prioritized for restoration and protection. Ultimately, resource managers must determine if the decreased level of accuracy obtained from abridged plant lists is an acceptable trade-off for increased savings in time and effort.
... While native upland species are assigned higher C values than non-native upland species, species endemic to wetland habitats are given the highest C values, making this a useful classification attribute for assessing wetland plant diversity [25,26]. FQAI is a widely used diversity metric in studies of wetland plant communities [27][28][29], as its emphasis on "quality" of plant species makes it a useful indicator of the desirability of plant species composition in wetland ecosystems [30]. We calculated FQAI scores for quadrats following the methods of Ohio EPA [19], which define FQAI as: ...
Article
Full-text available
The diversity of plant species and their distribution in space are both thought to have important effects on the function of wetland ecosystems. However, knowledge of the relationships between plant species and spatial diversity remains incomplete. In this study, we investigated relationships between spatial pattern and plant species diversity over a five year period following the initial restoration of experimental wetland ecosystems. In 2003, six identical and hydrologically-isolated 0.18 ha wetland "cells" were constructed in former farmland in northeast Ohio. The systems were subjected to planting treatments that resulted in different levels of vascular plant species diversity among cells. Plant species diversity was assessed through annual inventories. Plant spatial pattern was assessed by digitizing low-altitude aerial photographs taken at the same time as the inventories. Diversity metrics derived from the inventories were significantly related to certain spatial metrics derived from the photographs, including cover type diversity and contagion. We found that wetlands with high cover type diversity harbor higher plant species diversity than wetlands with fewer types of patches. We also found significant relationships between plant species diversity and spatial patterning of patch types, but the direction of the effect differed depending on the diversity metric used. Links between diversity and spatial pattern observed in this study suggest that high-resolution aerial imagery may provide wetland scientists with a useful tool for assessing plant diversity.
... Previous studies in similar wetlands have focused on individual taxa rather than on plant communities (Álvarez-Rogel et al., 2007b;. However, plant communities contain more information than single species and are easier to map by means of remote sensors (O'Connell, 2003;Johnston et al., 2009). ...
Article
Full-text available
Semiarid Mediterranean saline wetlands are unique ecosystems sheltering high biodiversity. In the last decades, the expansion of irrigated lands has led to hydrological imbalances in Mediterranean catchments, causing wetland degradation. Vegetation composition assessment is considered an important tool for evaluating wetland ecological condition and can be mapped using remote sensing. This study aims to develop a condition index based on plant community composition suitable for semiarid Mediterranean saline wetlands, as well as to test the applicability of airborne multispectral remote sensors for discriminating plant communities. Characteristic plant communities of 12 wetlands were identified by means of ordination and classification analysis of plant taxa cover percentages obtained through fieldwork sampling. An index for assessing wetland ecological condition was developed based on the relationship between wetland plant community composition and watershed hydrological condition. Selected wetland plant communities were then mapped by means of remote sensing techniques using random forest algorithm for supervised classification of airborne images. Following this methodology, remote sensing served as a tool for wetland condition assessment at a regional scale.
... FQAI is a widely used biodiversity metric in studies of wetland plant communities (DeBerry, 2006;Matthews, 2003;Mushet et al., 2002). The emphasis on quality of plant species leads many researchers to conclude that FQAI provides a useful indicator of the desirability of plant species composition in wetland ecosystems (e.g., Bourdaghs et al., 2006;Chamberlain and Ingram, 2012;Johnston et al., 2009) We calculated FQAI scores for quadrats and cells following the methods of Ohio EPA (Andreas et al., 2004), which define FQAI as: ...
... Biological community metrics and indicator species have become very popular for classifying/estimating wetland quality. Among the many taxa proposed, vegetation may be the most widely used for wetland quality assessments and selecting reference sites (Rader et al. 2001; [U.S. EPA] U.S. Environmental Protection Agency 2002; Johnston et al. 2008Johnston et al. , 2009. ...
Article
Reference criteria are needed for wetland monitoring and assessment programs. We used field-collected vege-tation data from non-forested wetland sites in the south-central United States to establish preliminary criteria for identifying reference-quality wetlands in future surveys. Our analysis included three parts: (1) preliminary reference verification and metric ranking using boxplots and standardized effect size, (2) updating the putative reference sample and metric selection using Test Site Analysis, and (3) establishing refer-ence criteria from best-metric confidence intervals and indicator species combinations. The Floristic Quality Assessment Index most clearly distinguished the reference wetlands; an index value of at least 20 is recommended for future reference designations in the study region. Other potential reference criteria include a maximum of 3–5 % bare ground in the 100 m buffer, a moderately sensitive species assemblage (mean conservatism>5.0), a small percentage (<10 %) of tolerant species (coefficient of conservatism≤2), and high native richness (>22 species). Five single species, four pairs, and one triplet combination were extracted as potential indi-cators of reference sites from 70,375 combinations of 75 candidate species, offering an efficient alternative to sampling entire vegetation communities. The analysis framework in this case study could be useful for similar projects in other regions.
... (3) Does the method perform similarly among different community types? These questions have been explored in other regions (Bourdaghs et al. 2006, Cohen et al. 2004, Johnston et al. 2009, Matthews et al. 2005, Miller and Wardrop 2006, Nichols et al. 2006, Taft et al. 2006) and should be addressed for the Northeast. In the meantime, the Northeast has the basic ingredient to facilitate floristic quality assessment, a potentially valuable tool for restoration monitoring, site prioritization efforts, and identification of high quality natural areas. ...
Article
Full-text available
The floristic quality index is a widely used method for ecological condition assessments in the United States. The foundation of the index is the conservatism concept, which estimates a species' ecological sensitivity or propensity to occur in areas least altered by humans. Plant species are assigned coefficients of conservatism (CoC) where ruderal and exotic species receive the lowest scores, competitors and matrix species intermediate scores, and remnant-dependent species the highest scores. The method has spread to over half of the United States, but New York and New England still lack CoC coverage. With funding from the Environmental Protection Agency and using nine of the region's most experienced botanists, an effort was undertaken to select CoC for the complete vascular flora of each New England state and New York State. Frequency distributions and rank correlations of CoC varied widely among states, except that each flora contained a large proportion of exotic species. Few taxa were scored with low confidence, although CoC at the extreme ends of the scale tended to be scored with higher confidence than more intermediate CoC. Differences in mean CoC and other summary measures for two botanists working independently on the same state indicate estimator bias in the ranking process, and calls for additional expert opinions, more careful instruction, and calibration of botanists, or the use of objective scoring methods.
... These findings indicate the utility of adult Odonata as a meaningful and robust indicator of freshwater wetland condition. In addition to developing the CoC and testing the OIWI in other regions, future studies should compare the OIWI with the related floristic quality indices Taft et al., 2006), and with multi-metric or multi-taxa indices (e.g., Brazner et al., 2007;Johnston et al., 2009) to evaluate how wetland assessments involving only adult odonates perform in relation to approaches requiring more taxa and expertise. ...
... We used an area-proportional, random sampling methodology similar to the those of Sluis (2002) and Johnston et al. (2009) to give equal opportunity to capture each of the four patchy vegetation zones; our method differed in the length of the segments used to divide the baseline and transects and the minimum number of quadrats sampled per site (Fig. 2). At each site, a baseline was drawn across the longest portion of the adjusted perimeter in ArcMap (version 10.1, Environmental Systems Research Institute, Redlands, Site order was determined using a random number generator. ...
Article
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Prairie fens are globally vulnerable wetlands that are considered a conservation priority due to threats to their high biodiversity and hydrological functions. Establishing a thorough and repeatable plant sampling protocol is critical to evaluating conservation and management initiatives. Our goal was to evaluate a sample methodology designed to assess prairie fen plant diversity and determine if it produced results (1) representative of site diversity, (2) comparable among fens, and (3) efficient to collect. Nineteen fens between 8.5 and 28.4 ha were surveyed twice within one growing season during 2012 and 2013 field seasons using an area-proportional, random design. The turnover in species between spring and summer sampling periods within a site ranged from 8 to 50 %. Sample coverage of total estimated plant species richness ranged from 84.8 to 95.0 % with a mean of 90.1 %. We compared results from our area-proportional, random design to simulated random samples of 10, 15, 20, 25, 30, 35 and 40 quadrats per site. No significant difference was found in sample coverage per fen when using sampling rates of 25, 30, or 35 quadrats per site versus the area-proportional design. Shannon’s diversity index and floristic quality index differed by sample period and number of quadrats sampled per fen. Our sample design produced acceptable levels of coverage and facilitated comparisons across fens. Our methodology could be applied to future research, restoration monitoring, and conservation planning efforts in Midwestern prairie fens.
... Recent multi-step approaches towards addressing such concerns (e.g. Smith et al., 2001;Johnston et al., 2009) do not address propagation of uncertainty from one step to another, thereby resulting in inference that is less reliable than that from an integrated statistical methodology. Chiu & Guttorp (2006) proposed the SHIPSL approach, a statistically enhanced multimetric index construction scheme that improves various quantitative aspects of conventional indices (Dobbie & Dail, to appear), although it and others share unresolved issues such as non-transferability in space or time, and the need for follow-up analyses to determine its relationship with non-faunal (abiotic) variables in method evaluation or policy-making contexts. ...
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The ability to quantitatively assess the health of an ecosystem is often of great interest to those tasked with monitoring and conserving ecosystems. For decades, research in this area has relied upon multimetric indices of various forms. Although indices may be numbers, many are constructed based on procedures that are highly qualitative in nature, thus limiting the quantitative rigour of the practical interpretations made from these indices. The statistical modelling approach to construct the latent health factor index (LHFI) was recently developed to express ecological data, collected to construct conventional multimetric health indices, in a rigorous quantitative model that integrates qualitative features of ecosystem health and preconceived ecological relationships among such features. This hierarchical modelling approach allows (a) statistical inference of health for observed sites and (b) prediction of health for unobserved sites, all accompanied by formal uncertainty statements. Thus far, the LHFI approach has been demonstrated and validated on freshwater ecosystems. The goal of this paper is to adapt this approach to modelling estuarine ecosystem health, particularly that of the previously unassessed system in Richibucto in New Brunswick, Canada. Field data correspond to biotic health metrics that constitute the AZTI marine biotic index (AMBI) and abiotic predictors preconceived to influence biota. We also briefly discuss related LHFI research involving additional metrics that form the infaunal trophic index (ITI). Our paper is the first to construct a scientifically sensible model to rigorously identify the collective explanatory capacity of salinity, distance downstream, channel depth, and silt-clay content --- all regarded a priori as qualitatively important abiotic drivers --- towards site health in the Richibucto ecosystem.
... Thus, understanding gradients of NDVI variation and the factors that influence NDVI is critical for sustainable ecosystem management. Recent research is mostly focused on regional NDVI changes in response to rainfall during scattered years (Wang et al. 2010;Johnston et al. 2009;Gómez-Mendoza et al. 2008). Decadal trends in regional NDVI and changes in the factors that influence NDVI (such as hydro-climatological variables) are poorly understood. ...
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In this paper, correlations between vegetation dynamics (represented by the normalized difference vegetation index (NDVI)) and hydro-climatological factors were systematically studied in Lake Baiyangdian during the period from April 1998 to July 2008. Six hydro-climatological variables including lake volume, water level, air temperature, precipitation, evaporation, and sunshine duration were used, as well as extracted NDVI series data representing vegetation dynamics. Mann-Kendall tests were used to detect trends in NDVI and hydro-climatological variation, and a Bayesian information criterion method was used to detect their abrupt changes. A redundancy analysis (RDA) was used to determine the major hydro-climatological factors contributing to NDVI variation at monthly, seasonal, and yearly scales. The results were as follows: (1) the trend analysis revealed that only sunshine duration significantly increased over the study period, with an inter-annual increase of 3.6 h/year (p < 0.01), whereas inter-annual NDVI trends were negligible; (2) the abrupt change detection showed that a major hydro-climatological change occurred in 2004, when abrupt changes occurred in lake volume, water level, and sunlight duration; and (3) the RDA showed that evaporation and temperature were highly correlated with monthly changes in NDVI. At larger time scales, however, water level and lake volume gradually became more important than evaporation and precipitation in terms of their influence on NDVI. These results suggest that water availability is the most important factor in vegetation restoration. In this paper, we recommend a practical strategy for lake ecosystem restoration that takes into account changes in NDVI.
... As such, Site 16 and other alleged pine barrens vernal ponds can show floristic overlap with sedge meadows and shrub swamps and may lack diagnostic species (Bried and Edinger, 2009), making qualitative categorization difficult. Although the descriptions from Edinger et al. (2002) represent best available information, proper assessment and classification of these enigmatic wetlands may require a multi-scale, multivariate approach (e.g., Johnston et al., 2009). Other caveats to our analysis include inherently low replication (<10) in select categories, some difficulty with determination of connected wetland size, and large annual variation in hydrology. ...
... Thus, understanding gradients of NDVI variation and the factors that influence NDVI is critical for sustainable ecosystem management. Recent research is mostly focused on regional NDVI changes in response to rainfall during scattered years (Wang et al. 2010;Johnston et al. 2009;Gómez-Mendoza et al. 2008). Decadal trends in regional NDVI and changes in the factors that influence NDVI (such as hydro-climatological variables) are poorly understood. ...
... Plant environmental stressors include physical, chemical, and biological such as cold, heat, drought, waterlogging, salinity, alkalinity, (Xue et al., 2016). pollution, diseases, insects, and weeds (Johnston et al., 2009;Tamaoki et al., 2004) requiring defense mechanisms protecting against environmental stressors (Tamaoki et al., 2004;Pagano et al., 2021). These include regulation of plant's growth and development, metabolic regulation, production of free radical scavengers and other membrane-protection substances to maintain free-radical balance as shown through as A 14 C-labeled formaldehyde test (Giese et al., 1994a). ...
Article
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The wide use of hazardous formaldehyde (CH2O) in disinfections, adhesives and wood-based furniture leads to undesirable emissions to indoor environments. This is highly problematic as formaldehyde is a highly hazardous and toxic compound present in both liquid and gaseous form. The majority of gaseous and atmospheric formaldehyde derive from microbial and plant decomposition. However, plants also reversibly absorb formaldehyde released from for example indoor structural materials in such as furniture, thus offering beneficial phytoremediation properties. Here we provide the first comprehensive review of plant formaldehyde metabolism, physiology and remediation focusing on release and absorption including species-specific differences for maintaining indoor environmental air quality standards. Phytoremediation depends on rhizosphere, temperature, humidity and season and future indoor formaldehyde remediation therefore need to take these biological factors into account including the balance between emission and phytoremediation. This would pave the road for remediation of formaldehyde air pollution and improve planetary health through several of the the UN Sustainable Development Goals.
... Consequently, rigorous evaluation of index reliability and other quantitative aspects is difficult with conventional indices: for example, detecting relationships between health and environmental or impact-related covariates such as water depth or urbanization; and formally assessing the uncertainty in these estimates of health. Recent multistep approaches towards addressing such concerns (e.g., [11,14]) do not address propagation of uncertainty from one step to another, thereby resulting in inference that is less reliable than that from an integrated statistical methodology. Chiu and Guttorp [8] proposed the SHIPSL approach, a statistically enhanced method to construct multimetric indices. ...
Article
Full-text available
The ability to quantitatively assess ecological health is of great interest to those tasked with monitoring and conserving ecosystems. For decades, biomonitoring research and policies have relied on multimetric health indices of various forms. Although indices are numbers, many are constructed based on qualitative procedures, thus limiting the quantitative rigor of the practical interpretations of such indices. The statistical modeling approach to construct the latent health factor index (LHFI) was recently developed. With ecological data that otherwise are used to construct conventional multimetric indices, the LHFI framework expresses such data in a rigorous quantitative model, integrating qualitative features of ecosystem health and preconceived ecological relationships among such features. This hierarchical modeling approach allows unified statistical inference of health for observed sites (along with prediction of health for partially observed sites, if desired) and of the relevance of ecological drivers, all accompanied by formal uncertainty statements from a single, integrated analysis. Thus far, the LHFI approach has been demonstrated and validated in a freshwater context. We adapt this approach to modeling estuarine health, and illustrate it on the previously unassessed system in Richibucto in New Brunswick, Canada, where active oyster farming is a potential stressor through its effects on sediment properties. Field data correspond to health metrics that constitute the popular AZTI marine biotic index and the infaunal trophic index, as well as abiotic predictors preconceived to influence biota. Our paper is the first to construct a scientifically sensible model that rigorously identifies the collective explanatory capacity of salinity, distance downstream, channel depth, and silt-clay content-all regarded a priori as qualitatively important abiotic drivers-towards site health in the Richibucto ecosystem. This suggests the potential effectiveness of the LHFI approach for assessing not only freshwater systems but aquatic ecosystems in general.
... The resulting segments are then automatically reclassified into a fewer number of HFTs at a similarity level of 25% to obtain classes that are substantially different from each other [82], irrespective of their adjacency. For this, we used hierarchical clustering and Euclidean distance based on the mean and variance of the nine original biophysical variables, scaled prior to analysis. ...
Article
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Protected areas (PAs) need to be assessed systematically according to biodiversity values and threats in order to support decision-making processes. For this, PAs can be characterized according to their species, ecosystems and threats, but such information is often difficult to access and usually not comparable across regions. There are currently over 200,000 PAs in the world, and assessing these systematically according to their ecological values remains a huge challenge. However, linking remote sensing with ecological modelling can help to overcome some limitations of conservation studies, such as the sampling bias of biodiversity inventories. The aim of this paper is to introduce eHabitat+, a habitat modelling service supporting the European Commission's Digital Observatory for Protected Areas, and specifically to discuss a component that systematically stratifies PAs into different habitat functional types based on remote sensing data. eHabitat+ uses an optimized procedure of automatic image segmentation based on several environmental variables to identify the main biophysical gradients in each PA. This allows a systematic production of key indicators on PAs that can be compared globally. Results from a few case studies are illustrated to show the benefits and limitations of this open-source tool.
... Vascular plant species represent diverse adaptations, ecological tolerances, and life history strategies, and they integrate environmental factors, species interactions, and disturbance. Many disturbances are reflected in shifts in the presence or abundance of particular plant species (Magee and Kentula 2005;Johnston et al. 2008), plant functional or trait groups (Lopez and Fennessy 2002;Quétier et al. 2007), plant assemblages (Galatowitsch et al. 1999;Magee et al. 1999;DeKeyser et al. 2009;Johnston et al. 2009), or vegetation structural elements (Mack 2007), making vegetation a powerful indicator of wetland condition (Mack and Kentula 2010). Existing VMMIs or VIBIs have proven useful for monitoring condition and prioritizing conservation or management actions for specific wetland types at local or regional scales within the United States and elsewhere (e.g., DeKeyser et al. 2003;Reiss 2006;Mack 2007;Hargiss et al. 2008;Rothrock et al. 2008;Lemly and Rocchio 2009;Mack 2009;Veselka et al. 2010;Euliss and Mushet 2011;Genet 2012;Rooney and Bayley 2012;Deimeke et al. 2013;Wilson et al. 2013;Hernandez et al. 2015;Savage et al. 2015;Jones et al. 2016;Miller et al. 2016). ...
Article
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In 2011, the US Environmental Protection Agency and its partners conducted the first National Wetland Condition Assessment at the continental-scale of the conterminous United States. A probability design for site selection was used to allow an unbiased assessment of wetland condition. We developed a vegetation multimetric index (VMMI) as a parsimonious biological indicator of ecological condition applicable to diverse wetland types at national and regional scales. Vegetation data (species presence and cover) were collected from 1138 sites that represented seven broad estuarine intertidal and inland wetland types. Using field collected data and plant species trait information, we developed 405 candidate metrics with potential for distinguishing least disturbed (reference) from most disturbed sites. Thirty-five of the metrics passed range, repeatability, and responsiveness screens and were considered as potential component metrics for the VMMI. A permutation approach was used to calculate thousands of randomly constructed potential national-scale VMMIs with 4, 6, 8, or 10 metrics. The best performing VMMI was identified based on limited redundancy among constituent metrics, sensitivity, repeatability, and precision. This final VMMI had four broadly applicable metrics (floristic quality index, relative importance of native species, richness of disturbance-tolerant species, and relative cover of native monocots). VMMI values and weights from the survey design for probability sites (n = 967) were used to estimate wetland area in good, fair, and poor condition, nationally and for each of 10 ecoregion by wetland type reporting groups. Strengths and limitations of the national VMMI for describing ecological condition are highlighted.
... COCs range from zero to ten and indicate a plant's level of habitat-type fidelity and ecological tolerance. The subjectivity associated with assignment of COC values has led to skepticism from wetland scientists and managers ( Bourdaghs et al. 2006, Johnston et al. 2009). More objective plant assessments can also be utilized for the same purpose, which focus on specific plant physiology and chemistry (Newman et al. ...
Thesis
Wetlands are some of the most important ecosystems on the planet, and are often referred to as "kidneys of the landscape" because of their remarkable ability to filter contaminants, especially those introduced by human activity. Some of the most important cleaning tools in wetlands are the plants that inhabit them. In this series of studies, wetland plant response to human impact in the Lake George watershed of the Adirondack Mountains was investigated. Measured differences in plant morphology and tissue chemistry indicated the importance of using such measures to assess short-term responses to human impact within wetland ecosystems. Additionally, a case-study depicting ecosystem establishment pre- and post- planting in a constructed stormwater treatment wetland was described. Results from these studies prompted specific phytoremediation experiments using the small duckweed, Lemna minor. Throughout these studies, it was determined that L. minor can acclimate morphologically and physiologically to human-related nutrient availability, which subsequently affects nutrient uptake potential. Attempts were made to induce this same natural acclimation response under laboratory conditions.
... They provide natural and semi-natural habitats for rare fauna and flora and act as a refuge for wildlife diversity (Denny, 1994). However, human land use leads to habitat degradation (Johnston et al., 2009 ;Malekmohammadi & Jahanishakib, 2017), such as invasion by exotic or eutrophic indigenous species, disturbances due to intensive agriculture or development of late-successional vegetation stages due to land abandonment (Andrew & Ustin, 2009). Detecting and monitoring habitat degradation in its early stages is of major importance for land and biodiversity management (Walker & Smith, 1997). ...
Thesis
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La technologie drone est une nouvelle source de données de télédétection qui offre de nouvelles perspectives aux sciences de l'observation de la Terre. Elle permet un nouveau régime d'observation flexible et à très haute résolution spatiale qui apparaît comme complémentaire à celui des systèmes satellitaires et favorise l'application du changement d'échelle. Cette thèse a pour objectif d'évaluer l'apport des complémentarités entre drone et satellite pour le suivi des prairies humides - des milieux à fort enjeux écologiques et économiques. Pour cela, les principales synergies entre les données drone et satellite ont été identifiées dans la littérature scientifique. Un jeu de données multi-sources et multi-échelles alliant observations drone, satellitaires et in-situ a été constitué sur le site de la réserve régionale du marais de Sougéal, France. Ainsi, deux synergies adaptées au changement d'échelle - la "calibration de modèle" et la "fusion de données" - ont été appliquées à la cartographie de la structure des prairies humides - la distribution des communautés végétales et les dynamiques d'inondation. Les résultats montrent que le drone apporte une information sur la structure spatiale fine qui est utile pour dépasser les effets de pixels mixtes présents dans les données satellitaires. Par ailleurs, ces synergies facilitent la réalisation de représentations cartographiques qui intègrent la nature graduelle des milieux de prairies humides.
... Wetland ecologists also continue to explore the geography of wetland ecosystem functions within and among different landscape settings. There is a deep awareness that no two wetlands (fields) are the same and that variation in ecosystem function reflects the combination of constraints imposed by the hydrogeologic setting (Winter, 1999), topographic position (e.g., Brinson, 1993;Rosgen, 1994), and the extent of hydrologic alteration (Johnston et al., 2009;Mason et al. 2016). Similar paradigms likely apply to agricultural systems (Borch et al., 2010;Clague et al., 2019). ...
Technical Report
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Improving soil health has gained traction within the farming community because of its importance to long-term crop production and watershed health. To date, management focuses on in-field crop management practices such as reducing tillage, following 4R nutrient stewardship guidelines, and maximizing vegetative cover throughout the year. Guidelines do not address agricultural water management, despite that soil moisture primarily drives underlying soil health processes. In January 2020, STAC partnered with the Foundation for Food and Agriculture Research, West Virginia University’s Institute of Water Security and Science, The Nature Conservancy, and the Transforming Drainage partnership and convened experts to explore the importance of agricultural water management to achieving soil and watershed restoration goals.
... Increased frequency of extreme weather events will affect the safety offishers; damage homes, services and infrastructure, and many coastal ecosystems particularly in coastal areas . Johnston et al. (2009) states that the effects of climate change on fisheries will harm the least equipped to cope hence the need to device strategies to mitigate them. Brugere (2015) notes that not only will livelihoods and national economies need to cope with immediate changes and trade-offs imposed by climate change, but they will also need to evolve in a way that allows them to develop positive adaptation mechanisms. ...
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The effects of climate change on the incidence and severity of diseases on some agricultural crops in Nigeria between 2010 and 2014 were studied. The objective of the study was to assess the climatic dynamics on the incidence and severity of plant diseases for climate prediction purposes in Nigeria. Climatic data were collected from Nigerian Meteorological Agency, Ilorin and literatures were perused to assess the incidence and severity of pathogens of agricultural crops. The results showed that in 2010 through 2014, average temperature varied from 16.6–7.7 °C; average cloud ranged from 4.0–7.1 okta; average relative humidity ranged from 48–90%; average rainfall ranged from 0.0–511.7 mm and average sunlight intensity ranged from 2.99–8.73 h. The results of the incidence and severity of crop disease pathogenic organisms revealed that in 2010, nematode prevalence ranged between 1.02–6.07% (yam tuber gall); 21.73–82.53% (root gall nematode) in 2012; 8.4% (tuber gall), 25.68% (dry rot) in 2014. The incidence and severity of fungi diseases ranged from 15.7–30.0% (powdery mildew) in 2010; 7.35% (leaf rot) in 2011; 37.33–48.0% (anthracnose) in 2012; 1.7–26.7% (anthracnose) in 2013. The incidence and severity of bacteria diseases ranged from 10.0–45.58% (bacteria disease on potato) in 2010; 16.7–31.3% (leaf spot on okra); 10.0–33.3% (leaf spot on Eggplant); 21.3% (bacteria wilt on okra) in 2013. The incidence and severity of virus disease ranged from 10.0–44.5% (potato virus) in 2010; 43.0–79.0% (virus disease) in 2011; 40–100% (maize streak) in 2013; 16.0–97.0% (virus disease) in 2014. Favorable climate conditions enhanced disease development, resulting to higher disease incidence and severity; and vice versa.
... The VIBI-FQ scoring system is more accurate than the traditional VIBIs (Gara 2016). Additionally, because the FQAI weighs species by assigning higher values to rare and specialist species, it is a useful indicator of the specificity of the plant community (Johnston et al. 2009;Brandt 2013). Vegetation species, cover, and biomass data were put into the automated spreadsheet to calculate VIBI-E and VIBI-FQ scores. ...
Article
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Wetland restorations have become an important tool in ecosystem management and have contributed to stabilizing hydrology and nutrient cycles, increasing native plant cover, and improving water quality. Long-term monitoring is essential for evaluating the success of a wetland restoration. However, wetland restorations are often monitored for short time periods compared to the timescale on which some abiotic factors change. Vegetative and avian assessments were conducted for a partially restored wetland on a reclaimed mine site, located at The Wilds® in Cumberland, Ohio. These assessments were performed from June through August 2018, 7 years after the initial restoration, using the unrestored portion as a comparison to evaluate restoration effectiveness. The restored wetland is characterized by open water with emergent vegetation, whereas the unrestored portion is largely a dense cattail (Typhus spp.) stand with low levels of standing water. The vegetative surveys used the Ohio EPA's Vegetation Index of Biotic Integrity for Emergent Vegetation (VIBI-E) and the bird surveys used a modified point count method. VIBI-E data are available for the study wetland from 1 year before restoration until summer 2018, while the avian study represents the first bird point count survey in the 2 wetland categories. The year 7 VIBI-E score of the restored section was the highest it has been since the restoration occurred and indicated "good" quality based on Ohio EPA scoring. The year 7 VIBI-E of the unrestored section has not changed since monitoring started and indicated "restorable" quality. The bird surveys showed higher richness associated with the restored wetland areas. These results demonstrate both the ecological value of wetland restoration and the ability for wetland restoration to maintain the ecological benefits over several years.
... Free-floating, floating-leaved, emergent, and submergednonvascular and vascular macroscopic plants (Richardson and Vymazal 2001) were surveyed once during each study period (Johnston et al. 2009;Kaeser and Kirkman 2009). Five parallel transects, extending from shoreline to shoreline, were established at equidistant locations. ...
Article
Landscape alterations can alter fish occurrence and abundance in wetlands. By increasing turbidity in wetland ponds, fishes can induce a shift from a clear- to a turbid-water state, resulting in reduced plant and amphibian abundance. In 2012, a drought reduced water levels and eliminated fishes from many wetlands of the prairie-pothole region (PPR) in the Midwestern United States. Our study objective was to evaluate if fish eliminations were associated with changes in wetland condition. A one-way ANOVA was used to compare the magnitude of change in parameters indicative of wetland condition (turbidity, plant cover and taxon richness, and tiger-salamander (Ambystoma tigrinum) biomass and numerical abundance) from 29 Iowa PPR wetlands between 2010 and 2011 (pre-drought) and 2014–2015 (post-drought) among wetlands where 1) all fishes were eliminated 2) large-bodied fishes were eliminated, 3) small-bodied fishes were eliminated, 4) fishes were retained, and 5) fishes were never detected. Turbidity decreased and plant cover increased more where large-bodied fishes were eliminated compared to the other groups. Changes in tiger-salamander biomass and abundance and plant-taxon richness were not different among groups. Results indicate that wetlands can shift from a turbid- to a clear-water state following drought and elimination of large-bodied fishes.
... They provide natural and seminatural habitats for rare fauna and flora and act as a refuge for wildlife diversity (Denny, 1994). However, human land use leads to habitat degradation (Johnston et al., 2009;Malekmohammadi and Jahanishakib, 2017), such as invasion by exotic or eutrophic indigenous species, disturbances due to intensive agriculture or development of late-successional vegetation stages due to land abandonment (Andrew and Ustin, 2009). Detecting and monitoring habitat degradation in its early stages is of major importance for land and biodiversity https://doi.org/10.1016/j.rse.2020.111780 ...
... It is now widely recommended that the interpretation of ecological condition using FQA metrics (such as mean C or C-W mean C) be assessed within relatively similar ecological community types (Bourdaghs 2012, Ervin et al. 2006, Johnston et al. 2009) because types differ in the degree to which generalist native species are part of the characteristic species combination. For example, because floodplain forests and salt marshes regularly experience flooding, they tend to have more generalist species even under natural disturbance regimes, and thus, high-quality examples of floodplain forests have lower mean C-values than bogs and fens (Bourdaghs 2012). ...
... Studies on wetland vegetation of the Great Lakes show that invasive species like European frogbit have made it difficult to distinguish individual plant communities from one another due to their broad distribution (Johnston et al. 2009). A study performed in a wetland reported introduced species including H. morsus-ranae would have a significant negative effect on the native plant community when they became dominant in the plant community (Houlahan and Findlay 2004). ...
Article
Aims European frogbit (Hydrocharis morsus-ranae L.) is an aquatic plant originating from Europe that has emerged as an invasive species, spreading in the USA and Canada since it was first brought to North America in 1932. It can now be found in many water bodies, from small ponds and long rivers to large lakes such as Lake Ontario and Lake Erie. The continuous spread of this species indicates its success as an invasive species despite legislative attempts to limit its distribution. Catling et al. (Catling PM, Miltrow G, Haber E, et al. (2003) The biology of Canadian weeds. 124. Hydrocharis morsus-ranae L. Can J Plant Sci 83:1001-16) wrote a thorough review about this invasive species in North America. Our review aims for a compilation of the most recent available data and recent studies on H. morsus-ranae L. and focuses primarily on its environmental uses, ecological impacts and management. The purpose of this review is to offer an organized and updated report on European frogbit that can be used towards future studies with the goal of eradicating this invasive species and providing insights on management of other invasive plants. Important Findings Our findings reveal that European forgbit's ecological effects on other species and the invaded environment were shown to be less harmful than previously feared. European frogbit had negative impacts on native plants and reduced dissolved oxygen concentration. However, water chemistry, phytoplankton and zooplankton communities were actually not affected by European frogbit. For fungi, bacteria and macroinvertebrates, studies have showed complex and sometimes conflicting results. We also specifically discussed the new method to control this species using shading and the more recent studies on biological control. Shading with a shade cloth has been shown to effectively remove European frogbit and had minor environmental effects. However, using biological control to combat the spread of the invasive frogbit seems not as successful as we wished. © The Author(s) 2018. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. All rights reserved.
... Free-floating, floating leaved, emergent, and submerged nonvascular and vascular macroscopic plants (Richardson and Vymazal 2001) were surveyed once annually (Johnston et al. 2009;Kaeser and Kirkman 2009). Five parallel transects, extending from shoreline to shoreline, were established at equidistant locations, each transect was divided into five sections of equal length, and a 1.0 m 2 sampling plot was randomly selected from each section. ...
Article
In the North American Prairie Pothole Region (PPR), agricultural and developed land uses may affect wetland condition by influencing contaminant inputs and invasions by fishes. To improve understanding of human impacts on wetlands, we quantified relationships between land use, physical attributes (herbicides, chloride, turbidity, wetland size), and biological attributes (tiger salamander [Ambystoma tigrinum] abundance; fish, plant, and invertebrate assemblages) of 45 permanently-ponded Iowa wetlands. Wetland area and water-column chloride concentration increased as cropped and developed land-covers increased in the watershed. However, we did not find strong relationships between land-cover type and biological attributes, with the exception of plant cover, which declined as water-column herbicide concentration increased. Fish abundance was an especially important determinant of wetland condition. As fish abundance increased, turbidity increased, and plant cover declined. Tiger salamander abundance and macroinvertebrate taxon richness also declined as fish abundance increased. Our findings suggest that in Iowa PPR wetlands, chloride concentration is an indicator of land-use intensity, and plant abundance can be predicted to some extent by herbicide concentrations. However, wetlands with low macroinvertebrate diversity, plant abundance, and salamander abundance tend to be those with high fish abundance.
... Vascular plant species represent diverse adaptations, ecological tolerances, and life history strategies, and they integrate environmental factors, species interactions, and disturbance. Many disturbances are reflected in shifts in the presence or abundance of particular plant species, plant functional or trait groups, plant assemblages, or vegetation structural elements making vegetation a powerful indicator of wetland condition (Johnston et al. 2009, Mack and Kentula 2010). In the NWCA, vegetation condition was assessed using a vegetation multimetric index or VMMI . ...
Article
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We analyzed data from 967 randomly selected wetland sites across the conterminous United States (US) as part of the 2011 National Wetland Condition Assessment (NWCA) to investigate the relative and attributable risk of various stressors on wetland vegetation condition. Indicators of stress included six physical stressors (damming, ditching, filling/erosion, hardening, vegetation removal, and vegetation replacement) and two chemical stressors (soil phosphorus and heavy metals) that represent a wide range of human activities. Risk was evaluated nationally and within four aggregate ecoregions and four aggregate wetland types. Nationally, all of the stressors except soil heavy metals and phosphorus had a significant relative risk but values were always < 2 (a relative risk of two indicates that it’s twice as likely to have poor vegetation condition when the stressor is present relative to when it is absent). Among the different ecoregions or wetland types, no one stressor was consistently riskier; all of the stressors were associated with poor vegetation condition in one or another of the subpopulations. Overall, hardening had the highest attributable and relative risks in the most different subpopulations. Attributable risks above 25% were observed for vegetation removal in the Coastal Plain, hardening and ditching in the West, and hardening in Estuarine Woody wetlands. Relative risks above 3 were noted for heavy metals and soil phosphorus in the Interior Plains, and vegetation removal, vegetation replacement, and damming in Estuarine Woody wetlands. Relative and attributable risk were added to the data analyses tools used in the NWCA to improve the ability of survey results to assist managers and policy makers in setting priorities based on conditions observed on the ground. These analyses provide useful information to both individual site managers and regional-national policy makers.
... The stabilized diatom data were clustered by hierarchical cluster analysis (HCA, Group-average linkage method) to classify the diatom communities into groups using Bray-Curtis similarity (Bray and Curtis, 1957). In order to examine diatom distribution patterns with relation to the habitat classification, non-metric multidimensional scaling (NMDS), an ordination technique for constructing sample maps whose inter-point distances have the same rank order as the corresponding dissimilarities between samples (Johnston et al., 2009), was applied with Bray-Curtis similarity to ordinate sites, using 25 restarts and a minimum stress of 0.01. Furthermore, analysis of similarities (ANOSIM) was used to determine the diatom composition of the four groups to test differences among habitats (Clarke, 1993). ...
Article
Benthic diatoms are useful indicators of the ecological state of river systems. To understand the factors determining benthic diatom metacommunity composition in urban rivers, we studied in situ surface sediment diatom communities from 23 rivers in Shanghai City. Based on our study results on the metacommunity structure of benthic diatoms and hierarchical cluster analysis (HCA), we found substantial differences between restored (G1) and unrestored rivers (G2-G4) in taxa richness, relative abundances, and dominant and indicator taxa of benthic diatoms. The epiphytic diatoms Cocconeis placentula and Amphora libyca var. baltica were representative of the restored rivers (G1), where aquatic macrophytes were more abundant and the water was clearer. The motile epipelic diatoms Navicula recens and Navicula germainii dominated the moderately polluted rivers (G2). The eutrophic taxa Cyclotella meneghiniana, Aulacoseira granulata, and Cyclostephanos tholiformis dominated in G3, which comprised relatively heavily polluted rivers with low organic matter sediment and high disturbance. The polysaprobic taxon itzschia palea and the halophilous taxon Fallacia pygmaea represented relatively heavily polluted rivers with a comparatively higher sedimentary salinity (SSal) (G4). Redundancy analysis (RDA) revealed that total phosphorus (TP), dissolved organic carbon (DOC), silicon dioxide (SiO2), dissolved oxygen (DO), Secchi depth (SD), SSal, and the ratio of carbon to nitrogen (C/N) in the sediment were important environmental factors explaining variation among benthic diatom metacommunity composition. Partial RDA (pRDA) implied that the relative importance of environmental factors in structuring benthic diatom metacommunity was much higher than spatial factors. Classification and regression trees (CART) further indicated that DOC, the sediment C/N ratio, and SSal were the key local environmental factors affecting grouping patterns of benthic diatom metacommunities. Our study proposes that benthic diatom metacommunities respond to the complex characteristics of local environment in urban rivers and provides useful knowledge for consideration in the ecological monitoring of urban river systems.
Article
Louisiana contains nearly 40% of estuarine herbaceous wetlands in the contiguous United States, supporting valuable ecosystem services and providing significant economic benefits to the state and the entire U.S.A. However, coastal Louisiana is a hotspot for rapid land loss from factors including hurricanes, land use change, and high subsidence rates contributing to high relative sea-level rise. The Coastal Protection and Restoration Authority (CPRA) was established after major hurricanes in 2005 to coordinate coastal restoration in Louisiana and develop the Louisiana Coastal Master Plan. The LA Coastal Master Plan uses numerical modeling of multiple scenarios to select a suite of restoration projects based on maximum land area created and flood reduction (as proxies for ecosystem value). Using potential value to aquatic, terrestrial, and social resources our work compared habitat value of shallow open water areas to emergent wetland. While potential resource benefits varied by emergent wetland salinity type and emergent wetland versus water, they were similar, suggesting that restoration planning based primarily on wetland land area may not achieve the maximum possible ecosystem benefits. After nearly 20 years of integrated restoration planning in coastal Louisiana, a reassessment of restoration planning decision drivers may be beneficial to ensure maximum benefits from coastal restoration. As a result of the Deepwater Horizon oil spill, settlement funds will be a major support to coastal restoration in Louisiana for many years. Assessing potential habitat value to multiple natural and social resources in Louisiana has potential to maximize synergy with large northern Gulf of Mexico restoration programs. This article is protected by copyright. All rights reserved.
Chapter
Wetland landscapes and wetland watersheds are both general, flexible terms that are often used interchangeably; however, the boundaries of landscapes are less discrete than those of watersheds, which have specific drainage areas. In expansive flat topography, as in Florida and the US Upper Midwestern prairie pothole region, it is difficult to locate watershed boundaries, so the term landscape is more appropriate. Elsewhere, wetland catchments are easily defined, and it is useful to refer to watersheds whenever emphasizing the inseparable interactions between the water that flows downslope and collects to form wetlands. Here, we consider watersheds to be parts of larger landscapes, which we also call regions to emphasize their large spatial scale. Most of our examples are drawn from the USA, where we have the greatest experience. © Springer Science+Business Media B.V., part of Springer Nature 2018. All rights reserved.
Article
Depth-to-water-level (DTWL) measurements in shallow groundwater piezometers are commonly used to develop predictive relationships between wetland plant composition and the water regime. These analyses, however, implicitly use DTWL as a surrogate for the soil water regime within the root zone. We collected bi-weekly field measurements of DTWL and surface effective saturation (SES) at a riparian wetland (3–4 years after restoration) in southwestern Wisconsin during the 2009 and 2010 growing seasons. Plant species composition was also sampled at the same locations (N = 62). Nonmetric multidimensional scaling (NMS) and nonparametric multiplicative regression (NPMR) were used to compare how effectively the two hydrological metrics explain the overall plant community ordination space (NMS) and predict the probability of presence of certain dominant species (NPMR). In addition, we performed each statistical method on each year's data separately in order to estimate the robustness of the metrics to predict species composition. Both SES and DTWL metrics were significantly correlated with one NMS axis for both years, although correlations were higher and more significant (p < 0·001) with the SES metrics. NPMR-generated models were created for six representative species using the SES and DTWL metrics as predictor variables. Models created using the SES metrics had consistently higher evaluation metrics for both years as compared with the DTWL metrics. While the metrics that consistently led to models with the highest evaluation metric (logβ > 2·2) for each of the species were mean and minimum SES, models that used mean SES were more temporally consistent and, therefore, more generally applicable. Copyright © 2011 John Wiley & Sons, Ltd.
Article
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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Hydrologic changes have facilitated increased fish abundance in wetlands of the North American prairie pothole region (PPR). Declines in PPR wetland condition have been attributed to fish-generated changes in trophic state, and reduced abundance and diversity of plants, invertebrates, and non-fish vertebrates. We sought to gain insight into mechanisms for fish impacts on wetland condition by evaluating their direct and indirect effects on invertebrates and salamanders. We quantified relationships among trophic state variables (chlorophyll a, nitrogen, phosphorus, total suspended solids, turbidity); fish and larval tiger salamander biomass; plant cover and taxon richness; and invertebrate density, biomass, and taxon richness in 34 continuously-flooded wetlands in Iowa. Path analysis results supported hypotheses that fish indirectly caused declines in invertebrate taxon richness by increasing turbidity, which in turn reduced plant cover. Path analysis results also supported the hypothesis that fish directly reduced salamander biomass by predation. Fish biomass increased with increasing water depth. Therefore, deeper wetlands were generally in poorer condition than relatively shallow ecosystems. Our findings support conclusions of previous investigators that regardless of other management strategies, actions limiting fish biomass in PPR wetlands (e.g., eliminating surface-water connections to other aquatic systems) are essential to restore health and functions of these ecosystems.
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The integration of rapid assessment methods with probability-based regional survey designs provides a cost-effective means for making unbiased assessments of wetland condition over a relatively large area within a short period time. We demonstrated this synergy through a statewide probability-based survey of the condition of perennially tidal saline estuarine wetlands (salt marshes) in California using the California Rapid Assessment Method (CRAM). An estimated 85% of the State’s salt marshes scored within the top 50% of possible CRAM index scores. Among the four CRAM attributes for salt marshes, Buffer and Landscape Context had the highest scores. Physical Structure was the attribute for which California’s salt marshes scored the lowest. CRAM index and attribute scores showed a general decrease from northern to southern California. The presence of dikes, levees, and other water control structures that restrict tidal exchange was a severe stressor that is responsible for low physical structure scores. Urbanization of surrounding land uses was significantly correlated to poor wetland health statewide. Information on landscape and local stressors gathered via the CRAM assessment suggest possible management actions that could be used to improve wetland health. This study demonstrates how incorporation of a rapid assessment method into a regional, probability-based survey can be used as context for evaluating the condition of wetland restoration projects.
Chapter
Rural people living in coastal zones of developing countries depend on climate-sensitive occupations. Changes in climate have affected most human and natural activities, fisheries inclusive. The fisherfolk have therefore become more vulnerable to the effects of climate change. This paper examined the factors that predispose fishermen to vulnerability and assesses the various adaptive strategies used by fisheries-based livelihoods to cope with the impact of climate variability and change in Lagos State, Nigeria. The two stage stratified sampling method was used to select 247 fishers located in the three Agricultural Development Programme zones in the state. Copies of a questionnaire were used for data collection at household level. These were analysed using descriptive statistics. Fishermen encountered several forms of vulnerability due to climate change, such as seasonality in fishing, loss of fishing inputs and family members to natural disasters/accidents. Others include hostility by members of host communities to migrants, injury and breakdown of health as well as susceptibility to STDs and HIV/AIDS. Decision to migrate as a result of climate change was made by 74.5% of the fishermen and 64.8% did not want the climate to keep on changing because it was not considered favourable. Some of the preferred adaptive strategies were timely access to information on climate change, alternative businesses, and saving for the future.
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We determined the influence of habitat, landscape, geographic, and climate variables on Sedge Wren (Cistothorus platensis) and Marsh Wren (C. palustris) occurrence in 840 coastal wetland survey points throughout the Great Lakes. Variables included surrounding land use and configuration out to 2000 m; latitude; longitude; temperature; precipitation; and vegetation characteristics within 100 m. Classification trees predicted Sedge Wren occurrence at points in the western Great Lakes with < 11 km of roads within 1000 m. Emergent herbaceous wetland within 500 m, woody wetland within various distances, and sedge within 100 m were also positively associated with Sedge Wren occurrence. Marsh Wren occurrence was predicted at points in the southern Great Lakes with < 42% developed land within 500 m. Emergent herbaceous wetland within 500 m, cropland within various distances, and cattail within 100 m were also positively associated with Marsh Wren occurrence. Our results suggest limiting development around wetlands is important for conserving these bird species throughout Great Lakes coastal wetlands. Landscape-scale land cover variables are easily obtainable and significantly increase our ability to predict occurrence of these species across a broad geographic scale.
Chapter
Wetland landscapes and wetland watersheds are both general, flexible terms that are often used interchangeably; however, the boundaries of landscapes are less discrete than those of watersheds, which have specific drainage areas. In expansive flat topography, as in Florida and the US Upper Midwestern prairie pothole region, it is difficult to locate watershed boundaries, so the term landscape is more appropriate. Elsewhere, wetland catchments are easily defined, and it is useful to refer to watersheds whenever emphasizing the inseparable interactions between the water that flows downslope and collects to form wetlands. Here, we consider watersheds to be parts of larger landscapes, which we also call regions to emphasize their large spatial scale. Most of our examples are drawn from USA, where we have the greatest experience.
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Soil nematode community composition could change following the conversion of wetlands to agricultural fields. In Jinchuan Wetland of Changbai Mountain area, China, we investigated the soil nematode community in different types of wetland-farmland interaction. Our results suggest that the Shannnon–Weaver diversity index in OW, R30, R1, KN, KP and PF are 2.48, 1.65, 1.70, 1.68, 1.39, 1.98, respectively, which means the native wetland had great biodiversity abundance. The genus of nematodes initially increased upon recovery from farmland, and nematode densities decreased in the tillage and cropping wetlands. Wilsonem and Prismatolaimus were sensitive to tillage. The bacterial-feeder nematodes increased after the first tillage treatment, while the nematode community was in a relatively stable state after a return to wetland following 30 years of agriculture. Plant parasite index (PPI) had about tenfold reduced in paddy farmland in comparison to the original wetland, and the values were positively associated with the change extent of recovery to reclamation of wetland. The study showed that agricultural activities disturbed the diversity of soil nematodes in Jinchuan Wetland. Certain kinds of genus and trophic diversity of the nematode community could indicate the effects of paddy cultivation on the wetland soil ecosystem.
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In light of extensive human impact on wetlands it is necessary that we develop an effective way to monitor the effects of impact in order to prevent further destruction. One method is plant community assessment, specifically Floristic Quality Assessment (FQA), which is common, but can be subjective. In this case study, we implement FQA, as well as specific morphological and chemical assessment measures over a two-year period in order to compare two wetlands in the Lake George watershed in the Adirondack mountains and their response to human impact. While the wetlands studied demonstrated very different water chemistry profiles makeups, FQA did not reveal substantial differences between plant communities. However, more specific analyses of plant morphology and tissue chemistry did reveal significant differences that reflected the level of impact at these two sites. Namely, the simple plant Lemna minor had consistently shorter roots and Nuphar lutea contained higher amounts of nitrogen in above ground tissues when growing in an anthropogenically impacted wetland. We suggest that FQA and specific plant morphology and tissue chemistry measurements be performed concurrently to provide indication of both long- and short-term effects of human impact in wetland ecosystems.
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ABSTRACT: Metric (eigenanalysis) and nonmetric multidimensional scaling strategies for ecological ordination were compared. The result, based on simulated coenoplane data showing varying degrees of species turnover on two independent environmental axes, suggested some strong differences between metric and nonmetric scaling methods in their ability to recover underlying nonlinear data structures. Prior data standardization had important effects on the results of both metric and nonmetric scaling, though the effect varied with the ordination method used. Nonmetric multidimensional scaling based on Euclidean distance following stand norm standardization proved to be the best strategy for recovering simulated coenoplane data. Of the metric strategies compared, correspondence analysis and the detrended form were the most successful. While detrending improved ordination configurations in some cases, in others it led to a distortion of results. It is suggested that none of the currently available ordination strategies is appropriate under all circumstances, and that future research in ordination methodology should emphasize a statistical rather than empirical approach.
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Classification and regression trees are ideally suited for the analysis of complex ecological data. For such data, we require flexible and robust analytical methods, which can deal with nonlinear relationships, high-order interactions, and missing values. Despite such difficulties, the methods should be simple to understand and give easily interpretable results. Trees explain variation of a single response variable by repeatedly splitting the data into more homogeneous groups, using combinations of explanatory variables that may be categorical and/or numeric. Each group is characterized by a typical value of the response variable, the number of observations in the group, and the values of the explanatory variables that define it. The tree is represented graphically, and this aids exploration and understanding. Trees can be used for interactive exploration and for description and prediction of patterns and processes. Advantages of trees include: (1) the flexibility to handle a broad range of response types, including numeric, categorical, ratings, and survival data; (2) invariance to monotonic transformations of the explanatory variables; (3) ease and robustness of construction; (4) case of interpretation; and (5) the ability to handle missing values in both response and explanatory variables. Thus, trees complement or represent an alternative to many traditional statistical techniques, including multiple regression, analysis of variance, logistic regression, log-linear models, linear discriminant analysis, and survival models. We use classification and regression trees to analyze survey data from the Australian central Great Barrier Reef, comprising abundances of soft coral taxa (Cnidaria: Octocorallia) and physical and spatial environmental information. Regression tree analyses showed that dense aggregations, typically formed by three taxa, were restricted to distinct habitat types, each of which was defined by combinations of 3-4 environmental variables. The habitat definitions were consistent with known experimental findings on the nutrition of these taxa. When used separately, physical and spatial variables were similarly strong predictors of abundances and lost little in comparison with their joint use. The spatial variables are thus effective surrogates for the physical variables in this extensive reef complex, where information on the physical environment is often not available. Finally, we compare the use of regression trees and linear models for the analysis of these data and show how linear models fail to find patterns uncovered by the trees.
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We collected water quality, land use, and aquatic macrophyte information from 62 coastal and inland wetlands in the Great Lakes basin and found that species richness and community structure of macrophytes were a function of geographic location and water quality. For inland wetlands, the primary source of water quality degradation was inputs of nutrients and sediment associated with altered land use, whereas for coastal wetlands, water quality was also influenced by exposure and mixing with the respective Great Lakes. Wetlands within the subbasins of the less developed, more exposed upper Great Lakes had unique physical and ecological characteristics compared with the more developed, less sheltered wetlands of the lower Great Lakes and those located inland. Turbid, nutrient-rich wetlands were characterized by a fringe of emergent vegetation, with a few sparsely distributed submergent plant species. High-quality wetlands had clearer water and lower nutrient levels and contained a mix of emergent and floating-leaf taxa with a diverse and dense submergent plant community. Certain macrophyte taxa were identified as intolerant of turbid, nutrient-rich conditions (e.g., Pontederia cordata, Najas flaxilis), while others were tolerant of a wide range of conditions (e.g., Typha spp., Potamogeton pectinatus) occurring in both degraded and pristine wetlands.
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In this paper we explore the potential for developing plant-based indicators for key dimensions of wetland stress, including 1) hydrologic flow modification (through water-level regulation and diking), 2) water quality degradation (through nutrient loading and sedimentation), and 3) ecological structural breakdown or physical degradation. Based on a review of the literature, we identify species or species groups that potentially function as indicators of individual dimensions of anthropogenic stress and propose floristic metrics for monitoring wetland health. We then examine the utility of these metrics for evaluating wetland disturbance at both regional and local scales, utilizing a database of wetland sites spanning the entire U.S. Great Lakes shoreline. We conclude that multiple dimensions of wetland disturbance can be measured based on coverage values of key aquatic plants.
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Aquatic plants were sampled in five coastal wetlands of northern Lake Huron during July 1996, 1997, and 1998. Mean annual water levels of Lake Huron changed during this period from 176.37 m (below the long-term average) in January 1996 to above average water levels of 176.83 m in July 1996 to 177.19 m in July 1997 and then declined to 176.88 m by July 1998. Boundaries of plant zones as indicated by distribution of the 1–3 dominant species along permanently established transect points across the wetland did not shift spatially over this 3-year period. Instead, relative abundance (percent of total stems per three 0.25 m2 quadrats per plot) and presence/absence of plant species responded individually to water level changes within major zones. In 1996, the first season sampled, the wet meadow had recently been inundated by rising water level. In 1997, after more than a year of above average and rising water levels, emergent stem densities were reduced in the Carex/Calamagrostis (sedge/blue-joint) dominated wet meadow and mixed transition sedge, narrow-leafed cattail, and hardstem bulrush (Carex, Typha angustifolia, and Schoenoplectus acutus) dominated zones compared to stem densities in 1996. Stem densities remained low in 1998, even though water levels dropped 31 cm from 1997 levels. The relative dominance (% of stems/3 quadrats/plot) and presence/absence of some plant species changed rapidly in the wet meadow zone in response to increases in water levels in 1997 and to decreases in water levels in 1998. In contrast, changes in emergent species were minimal in the deeper emergent zone dominated by hardstem bulrush. We conclude that temporary flooding and drying in response to water level changes are critical to maintaining a diverse arrray of plant species in the wet meadow zones of these marshes. Furthermore, short-term water level changes do not affect the relative spatial position of major plant zones within the marsh nor the relative abundance of emergent species in the deepest zone.
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Compensatory mitigation for damages to wetlands in the United States occurs largely without explicit analysis and replacement of wetland functions. We offer an approach to standardize such analyses and strengthen the connection between ecological principles and policies for wetland resources. By establishing standards from reference wetlands chosen for their high level of sustainable functioning, gains and losses of functions can be quantified for wetlands used in compensatory mitigation. Advantages of a reference wetland approach include (1) making explicit the goals of compensatory mitigation through identification of reference standards from data that typify sustainable conditions in a region, (2) providing templates to which restored and created wetlands can be designed, and (3) establishing a framework whereby a decline in functions resulting from adverse impacts or a recovery of functions following restoration can be estimated both for a single project and over a larger area accumulated over time. To establish reference standards, conditions inherent to highly functioning sites must be identified for classes of wetlands that share similar geomorphic settings. Ecological functions are then identified, and variables used to model the functions are employed in developing reference standards. Variables range from the highest levels of sustainable functioning to the complete absence of functions when a wetland ecosystem is displaced. An example given for wet pine flats in the North Carolina coastal plain illustrates how to determine the loss of a given function for an impacted wetland, how to calculate recovery (gains) in function through compensatory mitigation, and how to use the relationships between the two (loss vs. gain in function) to set minimum replacement ratios of restored to impacted area. In all cases, data from reference wetlands provide the benchmarks for making these estimates and for directing restoration or creation of wetlands toward the standards established for the wetland class. Programs to implement the use of reference wetlands require regional efforts that build upon the knowledge base of existing wetlands and their functioning.
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A hydrogeomorphic classification scheme for Great Lakes coastal wetlands is presented. The classification is hierarchical and first divides the wetlands into three broad hydrogeomorphic systems, lacustrine, riverine, and barrier-protected, each with unique hydrologic flow characteristics and residence time. These systems are further subdivided into finer geomorphic types based on physical features and shoreline processes. Each hydrogeomorphic wetland type has associated plant and animal communities and specific physical attributes related to sediment type, wave energy, water quality, and hydrology.
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We describe a method for using spatially referenced regressions of contaminant transport on watershed attributes (SPARROW) in regional water-quality assessment. The method is designed to reduce the problems of data interpretation caused by sparse sampling, network bias, and basin heterogeneity. The regression equation relates measured transport rates in streams to spatially referenced descriptors of pollution sources and land-surface and stream-channel characteristics. Regression models of total phosphorus (TP) and total nitrogen (TN) transport are constructed for a region defined as the nontidal conterminous United States. Observed TN and TP transport rates are derived from water-quality records for 414 stations in the National Stream Quality Accounting Network. Nutrient sources identified in the equations include point sources, applied fertilizer, livestock waste, nonagricultural land, and atmospheric deposition (TN only). Surface characteristics found to be significant predictors of land-water delivery include soil permeability, stream density, and temperature (TN only). Estimated instream decay coefficients for the two contaminants decrease monotonically with increasing stream size. TP transport is found to be significantly reduced by reservoir retention. Spatial referencing of basin attributes in relation to the stream channel network greatly increases their statistical significance and model accuracy. The method is used to estimate the proportion of watersheds in the conterminous United States (i.e., hydrologic cataloging units) with outflow TP concentrations less than the criterion of 0.1 mg/L, and to classify cataloging units according to local TN yield (kg/km 2 /yr).
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In tidal freshwater marshes of the Hudson River, coverage byPhragmites australis andLythrum salicaria has increased greatly over the past twenty years, althoughTypha angustifolia is still the predominant vegetation. Prior to any attempts at marsh restoration via removal of exotic/invasive plant species, we wanted to describe the current relationship between these plants and sediment nutrient pools. Extant stands (n=3 of each) ofT. angustifolia, L. salicaria, andP. australis were sampled with porewater equilibrators in the spring and summer of 1995 and summer 1996 to measure porewater ammonium, nitrate, and phosphate. Porewater pools of phosphate were significantly lower (p<0.05) in stands ofL. salicaria in summer, with concentrations only half those measured in stands ofP. australis andT. angustifolia. Porewater ammonium did not differ among plant communities, and nitrate was undetectable in sediments associated with all three communities. Sequestration of nutrients in above-ground biomass differed significantly among plant species, indicating differential demand on sediment nutrient pools. There were significant decreases in porewater ammonium from spring to summer. Growing season estimates of nitrogen incorporation into above-ground plant tissue are more than adequate to explain the removal of ammonium from porewater for all plant communities. Similarly, plant uptake of porewater phosphate was several times greater than springtime standing stocks of dissolved inorganic P. Concentrations of porewater phosphate remained high in the summer, indicating rapid replenishment from other sediment phosphorus pools. Depletion of porewater ammonium in the summer and low N:P in plant tissues suggest N limitation of these marsh plants. Our data suggest that marsh management practices intended to shift the relative vegetation coverage towards native and non-invasive species should consider the subtle but ecologically significant effects on nutrient cycling.
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A general understanding of how aquatic vegetation responds to water-level fluctuations is needed to guide restoration of Great Lakes coastal wetlands because inter-annual and seasonal variations often confound effects of costly remedial actions. In 1997, common carp (Cyprinus carpio) was removed from Cootes Paradise Marsh (L. Ontario) to reduce sediment resuspension and bioturbation, and thus regenerate marsh plants that had declined dramatically since the 1930s. Data from 1934 to 1993 were re-assembled from the literature to relate percentage cover of emergent vegetation to mean summer water level. A non-linear regression equation explained close to 90% of the variation compared with 80% for a non-linear equation, and this trend was confirmed for the dominant species, Typha latifolia. A modest recovery of emergent vegetation in 1999 following carp exclusion could have been predicted from declining water level alone, without invoking any effects of the biomanipulation. An unusually cool spring in 1997 delayed the migration of spawning planktivores into the marsh. This resulted in a grazer-mediated clear-water phase that coincided with a resurgence of the submersed aquatic vegetation (SAV) community in 1997, which declined again in 1999 when low water levels occurred. Even though decrease in water level was significantly related to increased suspended solids and greater light attenuation, light conditions appeared to have been adequate in marsh embayments to support SAV growth, according to a published relationship between maximum depth of SAV colonization and light extinction coefficient. I suggest that wave disturbance and propagule burial associated with shallow water depths may have been the main reasons for the decline of the SAV in 1999 and 2000.
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The coastal prairie ecoregion is located along the northwestern coastal plain of the Gulf of Mexico in North America. Because of agricultural and urban development, less than 1% of the original 3.4 million ha of this ecosystem type remains in native condition, making it one of the most endangered ecosystems in North America. The objective of this study was to characterize the vegetation and environmental relationships in a relatively pristine example of lowland coastal prairie in order to provide information for use in conservation and restoration. The study area was a small, isolated prairie located near the southern boundary of the coastal prairie region. Samples were taken along three parallel transects that spanned the prairie. Parameters measured included species composition, elevation, soil characteristics, indications of recent disturbance, above-ground biomass, and light penetration through the plant canopy. Fifty-four species were found in the 107 0.25-m2 plots and a total of 96 species were found at the site. Only two non-native species occurred in sample plots, both of which were uncommon. Cluster analysis was used to identify six vegetation groups, which were primarily dominated by members of the Poaceae or Asteraceae. A conspicuous, natural edaphic feature of the prairie was the presence of `mima' mounds, which are raised areas approximately 0.5 to 1m high and 5 to 10m across. Indicator species analysis revealed a significant number of species that were largely restricted to mounds and these were predominately upland and colonizing species. Ordination was performed using nonmetric, multidimensional scaling. The dominant environmental influence on species composition was found to be elevation and a host of correlated factors including those associated with soil organic content. A secondary group of factors, consisting primarily of soil cations, was found to explain additional variance among plots. Overall, this prairie was found to contain plant associations that are now rare in the surrounding landscape. Within the prairie, plant groups were largely separated by a suite of environmental conditions associated with topography. These results suggest that conservation and restoration efforts will need to carefully consider local topographic influences in order to be successful.
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Historical changes (1961-2002) in the distribution of herbaceous wetland plant associations were inferred from the hydrological regime of Lake Saint-Pierre, a 312 km2 broadening of the St. Lawrence River (Quebec, Canada), to assess the cumulative effects of human interventions and climatic variability. Relative abundance index (height × percent cover) of wetland plants in 630 field quadrats sampled at 13 sites (1999-2002) were used to derive a model predicting the occurrence of nine herbaceous plant classes with a 71% (24-84%) accuracy. Wetland types included seasonally dry (meadows), mudflats and wet (low marshes and submerged) assemblages. Over the 1961-2002 period, the total surface area of Lake Saint-Pierre herbaceous wetlands ranged between 11 (in 1972) and 128 (in 2001) km2 and was negatively correlated (Spearman r = -0.86, p < 0.0001) to average water level during the current growing season. Within-season variability and level conditions over the previous season defined 5 marsh assemblages characterized by different species composition, relative abundance and diversity. Significant hydrological variables included quadrat elevation, water depth, number of days flooded and depth variability experienced over the current and/or previous growth seasons. The hydrological model suggests that for a given level, wetland plant assemblages differed markedly whether the multi-year sequence of water levels was rising or falling. Lake Saint-Pierre alternated between three broad-scale wetland configurations, dominated by meadows and open marsh with floating-leaved vegetation (in the 1960s), scattered tall Scirpus marshes (in the 1970s and early 1980s) and closed marsh with aggressive emergents (since 1996). The strong response of Lake Saint-Pierre wetlands to hydrological conditions in the current and previous growth seasons underlines their vulnerability to future water level variations resulting from regulation and climate variability.
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Pattern and zonation of peatland vegetation are regulated by environmental gradients, as well as by effects of biomass and competitive exclusion on distribution of species richness. The interplay of these factors has not been closely examined in calcareous prairie fens, which are isolated, species rich, calcareous peatlands in the Prairie Peninsula region of North America. We used multivariate analyses to classify vegetation and to quantify species richness in relation to substrate conditions and vegetation structure in a 23-ha calcareous prairie fen in northeast Illinois, USA. Plant assemblages formed a floristic continuum across sedge meadow, graminoid fen, calcareous seep, marl flat, and spring run vegetation, with complete dissimilarity between spring run and sedge meadow. These vegetation zones corresponded to gradients of decreasing organic content and cation exchange capacity, and increasing pH, Na, Mg, and total Ca concentrations, which reach extremes in spring run and marl flats. Species richness was unimodal across the fen gradient, fitting an expected model of low richness in vegetation either with large biomass (as shown by low light penetration in tall sedge meadow) or with environmentally harsh conditions and low biomass (shown by high light penetration in short marl flat and spring run vegetation). These biotic and abiotic factors, as well as hydrology, mediate vegetation pattern across the fen.
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In the Upper Midwestern region of the US, three ecosystem services (flood abatement, water quality improvement, and biodiversity support) declined when about 60% of the region's historical wetland area was drained, mostly for agriculture. Some of the lost services could potentially be regained through wetland restoration measures authorized in the 2002 Farm Bill. Because no single wetland can provide all ecosystem services indefinitely, ecologists can help to identify combinations of projects that will best restore ecosystem services within watersheds. “Strategic” restoration would use an adaptive management approach, targeting former wetlands with marginal crop production, and prioritizing the location, size, and type of wetland needed for a watershed to provide optimal levels of all three services. Given that the Farm Bill includes over $1 billion per year to conserve natural resources on agricultural lands, we are in an excellent position to increase the effectiveness of wetland restoration.
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In the Upper Midwestern region of the US, three ecosystem services (flood abatement, water quality improvement, and biodiversity support) declined when about 60% of the region's historical wetland area was drained, mostly for agriculture. Some of the lost services could potentially be regained through wetland restoration measures authorized in the 2002 Farm Bill. Because no single wetland can provide all ecosystem services indefinitely, ecologists can help to identify combinations of projects that will best restore ecosystem services within watersheds. "Strategic" restoration would use an adaptive management approach, targeting former wetlands with marginal crop production, and prioritizing the location, size, and type of wetland needed for a watershed to provide optimal levels of all three services. Given that the Farm Bill includes over $1 billion per year to conserve natural resources on agricultural lands, we are in an excellent position to increase the effectiveness of wetland restoration.
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Using a comparative approach, we tested the prediction that relative competitive performance of plant species is correlated with distribution along natural gradients of fertility and standing crop. The mean position of 40 species of herbaceous plants along standing crop, phosphorus, nitrate, magnesium, potassium pH, and percent organic content gradients was calculated based on data from 217 quadrats from lake and river shorelines in Nova Scotia, Quebec, and Ontario. Competitive performance was measured in an outdoor experiments in which species were grown together with a common phytometer, Lythrum salicaria (n = 5 replicated per species). The relative ability of each species to suppress the growth of the phytometer was used as a measure of relative competitive performance. This measure of competitive performance was significantly correlated with the mean position of species on the standing crop (r = 0.081; P < 0.0001), percent organic content (r = 0.71; P < 0.0001); phosphorous (r = 0.70; P < 0.0001), nitrate (r = 0.67; P< 0.0001), magnesium (r = 0.66; P < 0.0001), and potassium gradients (r = 0.61; P < 0.0001). When monocotyledons and dicotyledons were considered separately, the relationship between distribution along the macronutrient gradients and competitive performance was much stronger for monocotyledons. It is suggested that this may reflect a differential influence of disturbance on distribution.
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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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Many current definitions of wetlands arise out of the regulatory need for rapid and accurate wetland delineation. These definitions focus on quickly observable characteristics that often lead to the perception that these are static environments that can be understood or re-created through attempts to reproduce these observable characteristics, rather than the processes responsible for them.
Article
Biological indicators of ecosystem integrity are increasingly being sought for use in ecosystem assessment and goal-setting for restoration projects. We tested the effectiveness of a plant community-based bioassessment tool, the floristic quality assessment index (FQAI) in 20 depressional wetlands in Ohio, USA. A priori, the 20 depressional wetlands were classified by type and ranked to form a disturbance gradient according to the local landscape condition. Ranks were based on surrounding land cover characteristics, vegetated buffer characteristics, and the extent of human-induced hydrologic alteration at the wetland site. The index was negatively correlated with the disturbance rank of a wetland and with the distance to neighboring wetlands (P = 0.01). Index values were lower for wetlands surrounded by agricultural or urban land use, wetlands with less vegetation on the wetland perimeter, and wetlands with more hydrologic modification, and at sites with greater distances to other wetlands. The wetlands with lower FQAI values tended to be dominated by plants that are typical of heavily cultivated landscapes or urban regions. Thus, the index is interpreted as a measure of environmental factors that maintain and control plant communities. The index was not correlated with differences in wetland surface water chemistry (alpha = 0.05) but was positively correlated with soil total organic carbon (P = 0.01), phosphorus (P = 0.05), and calcium (P = 0.05). Repeated wetland sampling in the summer and autumn revealed that the floristic quality assessment index could be useful for the assessment and monitoring of wetland ecosystems and for tracking wetland restoration projects over time.
Article
Habitat destruction and fragmentation have been identified as possible causes of large-scale amphibian declines. Here, we examine the effects of adjacent land use and water quality on wetland amphibian species richness, abundance, and community composition in 74 Ontario wetlands. Species richness was positively correlated with wetland area, forest cover, and the amount of wetlands on adjacent lands and negatively correlated with road density and nitrogen levels. The land-use effects peak at 2000-3000 m. Amphibian abundance was positively correlated with forest cover, distance to wetlands >20 ha, and amount of marsh habitat and negatively correlated with road density. The effects of adjacent land use were strongest at around 200 m. Land-use and water quality effects varied widely across species, although most species are positively correlated with forest cover and amount of wetlands on adjacent lands and negatively correlated with road density and water quality. These results suggest that the effects of adjacent land use on amphibian communities can extend over comparatively large distances. As such, effective wetland conservation will not be achieved merely through the creation of narrow buffer zones between wetlands and intensive land uses, but rather will require maintaining a heterogeneous regional landscape containing relatively large areas of natural forest and wetlands.
Article
Riparian wetlands are under heavy pressure from hydrological changes produced by dam construction and water diversion projects. There has been ample documentation of the relationship between the extent of flooding and the composition of shoreline plant communities, yet we have few models that allow us to predict the impact of altered flooding regimes on riparian wetlands. In the humid temperate zone, river regulation commonly affects the distribution of two major vegetation types: wooded wetland and herbaceous wetland. The practice of reducing peak floods and augmenting minimum river flows is often followed by the succession of herbaceous to wooded wetland. We used logistic regression models to describe the distribution of wooded wetland as a function of all possible combinations of seven hydrological variables. The variables were chosen to reflect the depth, duration, and time of flooding and were calculated for four different time intervals (3, 7, 12, and 18 growing seasons). Our best model was a combination of two variables: the last day of the first flood and the time of the second flood. For three of the four time intervals, the vegetation type was correctly identified as herbaceous or wooded for > 80% of the sample points. Our results suggest that models based on a few key environmental variables can be valuable tools in the conservation management of the vegetation of temperate and boreal zone wetlands.
Article
Natural disturbance related to fluctuating water levels governs the structure and composition of Saginaw Bay coastal wet meadow vegetation. European settlement introduced anthropogenic disturbance to the Saginaw Bay coastal zone, but the impact of anthropogenic disturbance on the vegetation is not known. We compared vegetation and abiotic data from six reference and six disturbed sites to examine anthropogenic impacts on Saginaw Bay coastal wet meadow vegetation. Reference sites were the least disturbed wet meadows available, whereas disturbed sites had suffered various anthropogenic impacts 10–30 years before the study started. We observed no significant difference in mean aboveground plot biomass, stem density, litter depth, hummock height and elevation, or mean site species richness, Shannon-Wiener diversity, coefficient of conservatism, and floristic quality between reference and disturbed sites. The importance values of only two of 15 major species differed significantly between reference and disturbed sites. Native wet meadow species re-vegetated previously disturbed sites, suggesting that Saginaw Bay coastal wet meadow vegetation is resilient once released from at least some forms of anthropogenic disturbance. Purple loosestrife (Lythrum salicaria L.) and several agricultural weeds occurred only in disturbed sites, suggesting a potentially useful metric for monitoring the health of Great Lakes coastal wet meadow vegetation. Additional studies are needed to gain insight into the probable revegetation trajectories of recently disturbed coastal wet meadows and to determine the form and utility of a “weedy plants” metric for classifying the condition of these wetlands.
Article
We compared the standing vegetation, seed banks, and substrate conditions in seven pairs of diked and undiked wetlands near the shores of Lake Michigan and Lake Huron, North America. Our analysis tested the null hypothesis that construction of artificial dikes has no effect on the vulnerability of Great Lakes coastal wetlands to non-native and native invasive species. Both the standing vegetation and seed banks in diked wetlands contained significantly more species and individuals of invasive plants. In addition, diked wetlands exhibited significantly higher levels of organic matter and nutrient levels, and significantly higher average pH. Two pervasive non-native invasive species in the Great Lakes region, Lythrum salicaria (purple loosestrife) and Phalaris arundinacea (reed canary grass) were significantly more abundant in diked wetlands. Typha spp. (cattail) also formed a much higher percent vegetation cover in the diked wetlands. Our results support the view that diking of shoreline wetlands modifies natural hydrologic regimes, leading to nutrient-rich aquatic environments that are vulnerable to invasion. The shallower, more variable water levels in non-diked wetlands, on the other hand, appear to favor another undesirable invasive species, Phragmites australis (common reed grass).
Article
Substantial effort in recent years has been invested in developing monitoring protocols and indicators for assessing the health of coastal wetlands of the Great Lakes. Most efforts have collected data exclusively in Great Lakes coastal wetlands and have not evaluated coastal wetland indicator development in the context of other wetland types in the state, province, or region. “Inland” freshwater wetlands are also subject to multiple hydrologic cycles of differing time scales and in some landscape contexts may be as hydrologically variable as Great Lakes coastal wetlands. The Ohio Environmental Protection Agency developed a Vegetation Index of Biotic Integrity (VIBI) for wetlands based on vascular plants as the indicator taxa group. The extension of the VIBI to Lake Erie coastal marshes was evaluated. Least-impacted Lake Erie marshes did not have significantly lower (or higher) scores (p < 0.001) although the upper 75th percentile of coastal wetland scores was not as high as the upper 75th percentile of inland wetland VIBI scores. Significant correlations (p < 0.01) were observed with two different human disturbance gradients in a combined data set of inland and coastal wetlands. Simultaneous metric evaluation using Principal Components Analysis showed some separation in metric performance between inland and coastal wetlands but also clear overlap, especially between reference-quality inland and coastal systems. Ordination of species presence and abundance data revealed similar patterns with some separation between inland and coastal wetlands but considerable overlap in species composition. Lake Erie coastal marshes represent another type of emergent marsh system. With minor modifications, the VIBI, developed with inland wetland data sets, worked well for assessing Lake Erie coastal wetlands in Ohio. The analysis of data from Ohio coastal wetlands with a larger inland reference data set shows the advantages of treating Great Lakes coastal wetlands as a type of freshwater wetland and working toward indicator development in the context of an overall state or provincial wetland classification and assessment program.
Article
Quantitative geomorphic methods developed within the past few years provide means of measuring size and form properties of drainage basins. Two general classes of descriptive numbers are (1) linear scale measurements, whereby geometrically analogous units of topography can be compared as to size; and (2) dimensionless numbers, usually angles or ratios of length measures, whereby the shapes of analogous units can be compared irrespective of scale. Linear scale measurements include length of stream channels of given order, drainage density, constant of channel maintenance, basin perimeter, and relief. Surface and crosssectional areas of basins are length products. If two drainage basins are geometrically similar, all corresponding length dimensions will be in a fixed ratio. Dimensionless properties include stream order numbers, stream length and bifurcation ratios, junction angles, maximum valley-side slopes, mean slopes of watershed surfaces, channel gradients, relief ratios, and hypsometric curve properties and integrals. If geometrical similarity exists in two drainage basins, all corresponding dimensionless numbers will be identical, even though a vast size difference may exist. Dimensionless properties can be correlated with hydrologic and sediment-yield data stated as mass or volume rates of flow per unit area, independent of total area of watershed.