Article

Rapid Invasion of a Great Lakes Coastal Wetland by Non-native Phragmites australis and Typha

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Abstract

Great Lakes coastal wetlands are subject to water level fluctuations that promote the maintenance of coastal wetlands. Point au Sauble, a Green Bay coastal wetland, was an open water lagoon as of 1999, but became entirely vegetated as Lake Michigan experienced a prolonged period of below-average water levels. Repeat visits in 2001 and 2004 documented a dramatic change in emergent wetland vegetation communities. In 2001 non-native Phragmites and Typha were present but their cover was sparse; in 2004 half of the transect was covered by a 3 m tall, invasive Phragmites and non-native Typha community. Percent similarity between plant species present in 2001 versus 2004 was approximately 19% (Jaccard's coefficient), indicating dramatic changes in species composition that took place in only 3 years. The height of the dominant herbaceous plants and coverage by invasive species were significantly higher in 2004 than they were in 2001. However, floristic quality index and coefficient of conservatism were greater in 2004 than 2001. Cover by plant litter did not differ between 2001 and 2004. The prolonged period of below-average water levels between 1999 and early 2004 exposed unvegetated lagoon bottoms as mud flats, which provided substrate for new plant colonization and created conditions conducive to colonization by invasive taxa. PCR/RFLP analysis revealed that Phragmites from Point au Sauble belongs to the more aggressive, introduced genotype. It displaces native vegetation and is tolerant of a wide range of water depth. Therefore it may disrupt the natural cycles of vegetation replacement that occur under native plant communities in healthy Great Lakes coastal wetlands.

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... Throughout North America, the invasive lineage of Phragmites australis (hereafter P. australis) is increasing in abundance and distribution (Catling and Mitrow, 2011). For example, in Lake Erie coastal marsh, P. australis took advantage of historically low lake levels during the 1990s (Tulbure et al., 2007;Tulbure and Johnston, 2010) and increased nutrient loading in the watershed (Croft and Chow-Fraser, 2007) to rapidly expand, primarily replacing cattail marsh (dominated by Typha spp.) and rare "Graminoid Coastal Meadow Marsh" (Imperiled [S2]; Ministry of Natural Resources Forestry, 2018; dominated by Calamagrostis canadensis) (Wilcox et al., 2003). These resident plant communities are naturally stratified by water depth with cattail marsh in deeper water (11-52 cm) and meadow marsh in shallower water (0-27 cm; Supplementary Materials 1), indicating the relatively broader niche of invasive P. australis. ...
... Phragmites australis forms dense monocultures that replace resident plant communities (Keller, 2000;Mal and Narine, 2004;Tulbure et al., 2007) and can negatively affect wetland birds (Robichaud and Rooney, 2017), amphibians (Greenberg and Green, 2013), and turtles (Bolton and Brooks, 2010;. The stem density of P. australis typically increases with age (Rooth et al., 2003), and while these negative effects on wildlife are reported from dense, established P. australis stands (e.g., 100 live stems m −2 ), some research suggests that at lower densities P. australis can provide habitat value (Meyer et al., 2010;Kiviat, 2013). ...
... We caution that, as suggested by Alldred et al. (2016), invasion by P. australis triggers a variety of opposing changes in wetland ecosystem services that reflect trade-offs among service types. A net assessment of the effects of P. australis invasion must also account for the resulting loss of plant biodiversity (Keller, 2000;Tulbure et al., 2007) and associated degradation of bird (Robichaud and Rooney, 2017) and turtle habitat . In economic terms, replacing biodiverse and rare meadow marsh habitat with P. australis-invaded marsh could increase carbon stocks by 3.87 T ha −1 and under future carbon pricing could reflect about $550 USD ha −1 in carbon savings. ...
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Invasive species are a threat to biodiversity and can cause ecological degradation, however, well-established invasive species may serve valuable ecological functions. For example, in the Laurentian Great Lakes, where nutrient pollution is a major issue, highly productive Phragmites australis (European Common Reed) may provide a nutrient retention service. Yet there is a lack of research comparing carbon and macronutrient stocks in P. australis with resident plant communities, such as cattail and meadow marsh. We quantified the effect of P. australis invasion on carbon and macronutrient standing stocks in a freshwater coastal marsh by comparing the above- and belowground biomass, tissue nutrient concentrations, and annual nutrient standing stocks in marsh invaded by P. australis with cattail marsh (dominated by Typha spp.) and meadow marsh (dominated by Calamagrostis canadensis), which are being displaced by P. australis in Lake Erie coastal marsh. We conclude that the effect of P. australis invasion on carbon and macronutrient standing stocks is dependent on the plant community being replaced. The annual standing stock of carbon, nitrogen, phosphorus, and potassium are consistent between cattail marsh and P. australis-invaded marsh, though cattail marsh contains more magnesium (112% mean increase) and calcium (364% mean increase). In contrast, when P. australis replaces meadow marsh, the standing stocks of all measured nutrients and carbon increase significantly (103–188% mean increase). Our study highlights that plant invasions may create trade-offs between ecosystem services. In our case, the increase in nutrient standing stocks when P. australis invades meadow marsh should be weighed against the documented reductions in biodiversity and habitat value.
... In the Laurentian Great Lakes region of Canada and the United States, coastal wetlands are subject to substantial physical, chemical, and anthropogenic stressors that frequently cause shifts in vegetation communities (Albert and Minc, 2004;Brazner et al., 2007;Danz et al., 2007;Frieswyk and Zedler, 2007;Hudon, 1997;Jean and Bouchard, 1993;Johnston and Brown, 2013;Tulbure et al., 2007;Wilcox and Nichols, 2008). 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). ...
... Naturally fluctuating water levels have historically maintained a rich diversity of plant species, but research has demonstrated that the stabilization of water levels through regulatory controls has increased the susceptibility of coastal wetlands to invasion by exotic species such as Typha spp. 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. ...
... Instead, we observe a homogenization of coastal wetland communities that results from replacement of native-dominated plant communities by invasive or colonizer plants such as P. australis and Typha spp. Recent studies recognize that P. australis, Typha spp., and P. arundinacea are effective invaders because of several factors, including production of abundant seed, ability to rapidly utilize nutrients such as nitrogen and phosphorus, taller stature than most natives, ability to colonize and persist through changes in water levels, and rapid expansion through rhizomes and/or stolons (Frieswyk and Zedler, 2007;Lishawa et al., 2010;Tulbure et al., 2007;Wilcox and Nichols, 2008). ...
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.
... Changes in lake levels and corresponding changes in the juxtaposition of vegetation and open water (water-vegetation interspersion) significantly influence the biota of coastal wetlands (Chin et al., 2014;Desgranges et al., 2006;Epstein et al., 2002;Frieswyk and Zedler, 2007;Rehm and Baldassarre, 2007). During years of high lake levels, for example, wetlands contain extensive areas of open water and submergent vegetation; whereas during low lake levels, submergent vegetation is often replaced by patches or continuous stands of emergent vegetation (Chin et al., 2014;Frieswyk and Zedler, 2007;Tulbure et al., 2007;Wilcox, 2004). Increasing lake levels may also increase plant diversity by inundating monocultures of wetland dominants like the invasive form of the common reed (Phragmites australis australis [Cav.] ...
... Trin. ex Steud.; Frieswyk and Zedler, 2007), which prefers shallow wetlands or wetland edges with periodically exposed substrates (Tulbure et al., 2007). The importance of water-level fluctuations for Laurentian Great Lakes coastal wetland ecology is well established. ...
... Great Lakes coastal wetlands selected for this study followed the selection criteria of the CWMP: 1) connected to and influenced by a Great Lake or connecting channel (e.g., through direct flow or wind-driven seiche), 2) at least 4 ha in size, and 3) dominated by herbaceous (nonwoody) vegetation (Gnass Giese et al., 2018;Uzarski et al., 2017). Depending on lake levels, dominant plants in these dynamic coastal wetlands typically include a mix of cattails (e.g., Typha spp.), bulrushes (e.g., Schoenoplectus spp.), grasses (e.g., Calamagrostis spp.), sedges (e.g., Carex spp.), and submergent plants (Chin et al., 2014;Tulbure et al., 2007;Wilcox, 2004). Recently, many of these wetlands have been invaded by aggressive exotic species, such as common reed, hybrid cattail (Typha  glauca Godr.), and reed canary grass (Phalaris arundinacea L.; Chin et al., 2014;Tulbure et al., 2007;Wilcox, 2004). ...
Article
Coastal wetlands in the Laurentian Great Lakes undergo frequent, sometimes dramatic, physical changes at varying spatial and temporal scales. Changes in lake levels and the juxtaposition of vegetation and open water greatly influence biota that use coastal wetlands. Several regional studies have shown that changes in vegetation and lake levels lead to predictable changes in the composition of coastal wetland bird communities. We report new findings of wetland bird community changes at a broader scale, covering the entire Great Lakes basin. Our results indicate that water extent and interspersion increased in coastal wetlands across the Great Lakes between low (2013) and high (2018) lake-level years, although variation in the magnitude of change occurred within and among lakes. Increases in water extent and interspersion resulted in a general increase in marsh-obligate and marsh-facultative bird species richness. Species like American bittern (Botaurus lentiginosus), common gallinule (Gallinula galeata), American coot (Fulica americana), sora (Porzana carolina), Virginia rail (Rallus limicola), and pied-billed grebe (Podilymbus podiceps) were significantly more abundant during high water years. Lakes Huron and Michigan showed the greatest increase in water extent and interspersion among the five Great Lakes while Lake Michigan showed the greatest increase in marsh-obligate bird species richness. These results reinforce the idea that effective management, restoration, and assessment of wetlands must account for fluctuations in lake levels. Although high lake levels generally provide the most favorable conditions for wetland bird species, variation in lake levels and bird species assemblages create ecosystems that are both spatially and temporally dynamic.
... High biomass (5093 g m À2 ) was recorded in 22 cm of water in the temperate Zhalong wetland, China (Zhang et al. 2013), and the tallest reported reeds (see V) grew in 10-cm-deep water in central Australia (mean water level within the stand was À4Á3 cm, 95% CI 17Á9-9Á2; Packer et al. 2017a). New populations typically establish on bare, unvegetated moist soils after water levels recede as deeper water (≥5 cm) is unsuitable for seed germination and seedling establishment (Tulbure, Johnston & Auger 2007;Whyte et al. 2008) but supports clonal growth (Alvarez, Tron & Mauchamp 2005). Phragmites australis is capable of persisting for many years in sites which have ceased to be wetlands , and rhizomes growing in floodplains can survive for approximately 10 years without flooding (Roberts 2000). ...
... 2-4 years) and brackish habitats (Pallis 1961;Haslam 1972). Stolons can be the primary mechanism of expansion by existing stands (Tulbure, Johnston & Auger 2007). ...
... Curtis (1959) found that annual rhizome lateral spread averaged 40 cm in Wisconsin, USA, but Farnsworth & Meyerson (1999) reported that in Connecticut, USA, P. australis spread through the recruitment of a dense phalanx of stems behind the advancing front rather than via exploratory runners. Legehalme can also contribute to rapid population expansion (Haslam 1972;Tulbure, Johnston & Auger 2007). Rudescu, Niculescu & Chivu (1965) suggest that clones might persist for up to 1000 years. ...
Article
This account presents comprehensive information on the biology of Phragmites australis (Cav.) Trin. ex Steud. (P. communis Trin.; common reed) that is relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors and to the abiotic environment, plant structure and physiology, phenology, floral and seed characters, herbivores and diseases, as well as history including invasive spread in other regions, and conservation. 2.Phragmites australis is a cosmopolitan species native to the British flora and widespread in lowland habitats throughout, from the Shetland archipelago to southern England. It is widespread throughout Ireland and is native in the Channel Islands. Native populations occur naturally in temperate zones and on every continent except Antarctica. Some populations in Australia and North America have been introduced from elsewhere and have become naturalized, and in North America some of these are known to be invasive where they compete with native local populations of P. australis. Typical habitats in Britain range from shallow still water along waterbody edges to marshlands, salt marshes and drier habitat on slopes up to 470 m above sea level. Additional habitats outside Britain are springs in arid areas (-5 m above sea level) and groundwater seepage points up to 3600 m above sea level. Although it occurs on a wide range of substrates and can tolerate pH from 2.5 to 9.8, in Britain it prefers pH >4.5 and elsewhere it thrives in mildly acidic to mildly basic conditions (pH 5.5–7.5). The species plays a pivotal role in the successional transition from open water to woodland. 3.Phragmites australis is a tall, helophytic, wind-pollinated grass with annual shoots up to 5 m above ground level from an extensive system of rhizomes and stolons. A single silky inflorescence develops at the end of each fertile stem and produces 500–2000 seeds. The plant is highly variable genetically and morphologically. 4.Expansion of established populations is mainly through clonal growth of the horizontal rhizome system and ground-surface stolons, while new populations can establish from rhizomes, stem fragments and seeds. Shoots generally emerge in spring, with timing determined primarily by physiology that is mediated by external conditions (e.g. local climate including frost). 5.Many populations in the British Isles have experienced some decline over the past two decades and there is concern that there might be further losses along the east coast as sea level rises. There has recently also been localized expansions, especially in highly modified habitats: where P. australis reedbeds have been planted as wildlife habitat, rehabilitated mineral- and gravel-beds, and bioremediation filter beds for industrial and transport infrastructure. Native populations outside Britain also demonstrate both types of trends: they are declining in many parts of Western Europe and North America, yet also colonise many disturbed, ruderal habitats (e.g. the edges of agricultural fields and motorways) throughout its native and non-native range and can form ‘weedy’ monodominant populations (e.g. in Australia and China). This article is protected by copyright. All rights reserved.
... The fluctuating water levels of the Great Lakes create pulse stable vegetation communities, maintaining diversity and habitat value not only for wetland plants but for fish, amphibians, reptiles and birds (Harris, 1988;Mitsch & Gosselink, 2000;. However, these fluctuations may also aid in the establishment of non-indigenous species such as Phragmites, that outcompete native vegetation during low-water levels or recovery periods Tulbure et al., 2007;Tulbure & Johnston, 2010;D. A. Wilcox, 2012;. ...
... A. Wilcox, 2012;. Suggested to colonize during periods of low water levels (Tulbure et al., 2007;D. A. Wilcox, 2012), Phragmites returns year after year with annual shoots and perennial rhizomes forming stands that become increasingly monotypic, dense and expand further into surrounding habitats Lemein et al., 2017;. ...
Thesis
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Invasive Phragmites australis ssp. australis (herein “Phragmites”) has established and rapidly spread throughout many coastal areas of the Great Lakes. Known to displace native vegetation communities as it forms large, monotypic stands, Phragmites has a bad reputation when it comes to losses of biodiversity and habitat provision for wildlife. However, the extent to which Phragmites provides habitat for fish and invertebrates in coastal freshwater wetlands remains relatively unquantified. Thus, this study assessed whether fish assemblages and invertebrate communities in stands of Phragmites differ from those in stands of two native emergent vegetation communities, Typha spp. and Schoenoplectus spp. The findings showed significant differences in habitat variables among the vegetation communities in terms of water depth, macrophyte species richness, stem density and water quality. While abundance of the functional feeding group filterer-collectors was found to be significantly less in stands of Phragmites when compared to Schoenoplectus, no difference was observed in invertebrate taxa richness among vegetation communities. Lastly, no difference in fish assemblage or invertebrate community was detected when using multivariate analyses, implying that invasive Phragmites provides habitat that appears to be as valuable for fish and invertebrates as other emergent vegetation types in the St. Clair River Delta. The findings of this study will ultimately benefit the literature on invasive Phragmites and its role as fish habitat in freshwater wetlands, and aid management agencies in decisions regarding control of the invasive species.
... There, the Eurasian genotypes are nowadays considered invasive, being in competition with the native populations referred to as P. australis subsp. americanus Saltonstall, P.M. Peterson & Soreng (Saltonstall, 2002;Saltonstall et al., 2004;Tulbure et al., 2007). Even in Europe, although in most cases explicit indications of infraspecific ranks are lacking, P. australis is often considered as an expansive species (Pro´chnicki, 2005;Foggi et al., 2011), and its control is considered an important aspect for the conservation of local biodiversity (Tomei et al., 2000;Foggi et al., 2014). ...
... In other studies, the alteration and/or artificial regulation of water levels were reported as possible causes of the reed decline (Ostendorp, 1989;Rea, 1996). Several processes can be related to prolonged submersion, such as reduction of carbohydrate availability (van der Putten, 1993; and an increase of eutrophication processes (Gabersˇcˇik et al., 2003), both negatively affecting common reed growth (Rea, 1996). Prolonged submersion can lead to an extreme lack of oxygen in the rhizosphere, favoring anoxia, production of phytotoxines (Ponnamperuma, 1984) and infection by pathogens (Nechwatal et al., 2008). ...
Article
The common reed die-back syndrome was formerly reported mostly in Central Europe and more recently in the Mediterranean basin. This study investigates a case of reed die-back in Central Italy through a Geographic Information System (GIS) diachronic survey and the analysis of macromorphological and ecological parameters. Data were recorded during field activities on ten plots randomly distributed according to two ecological statuses, permanently and temporarily flooded. Culm density, height and diameter, clumping habit, flowering head and dead apical bud number and rate were measured; for each plot, chemical parameters of sediments were analyzed. Information on interstitial waters for the flooded plots was also provided. Floristic-vegetational features of the reed-bed community such as the total vegetation cover, the species composition and abundance were estimated. Univariate and multivariate analyses were used to demonstrate differences between morphological traits of flooded and emerged stands and their relationships with the chemical features of sediment. Macromorphological traits differed according to the ecological status, with flooded stands showing patterns related to poor health status of Phragmites australis, such as high rates of clumping habit and dead apical bud rate, high culm density and, to a lesser extent, low culm diameter and flowering head rate. Sulfates were relatively abundant in the sediment of flooded stands and, together with some heavy metals, resulted in some of the mentioned traits. Our results showed a relationship between reed die-back and prolonged flooding and highlighted the potential role of some chemical parameters in affecting the growth of permanently flooded reeds.
... Typha is rapidly displacing native wetland communities in the Great Lakes region (Freeland et al. 2013;Frieswyk and Zedler 2007;Lishawa et al. 2010;Tuchman et al. 2009;Tulbure et al. 2007;Vaccaro et al. 2009), as it is able to spread rapidly (4-5 m/year; Boers et al. 2007;McDonald 1955) via rhizomatous growth and quickly dominate a wetland (Smith 1967;Tulbure et al. 2007). Our data suggest that the replacement of large tracts of diverse wetlands with monocultures of this highly productive macrophyte could alter the net radiative forcing of wetlands at a regional scale, given that soil methane emissions were at least three-times greater from Typha-invaded than native Soils collected from Typha-invaded stands had greather methane production potential than native wet meadows in three Midwestern wetlands (mean ± 1 SE; n = 5). ...
... Typha is rapidly displacing native wetland communities in the Great Lakes region (Freeland et al. 2013;Frieswyk and Zedler 2007;Lishawa et al. 2010;Tuchman et al. 2009;Tulbure et al. 2007;Vaccaro et al. 2009), as it is able to spread rapidly (4-5 m/year; Boers et al. 2007;McDonald 1955) via rhizomatous growth and quickly dominate a wetland (Smith 1967;Tulbure et al. 2007). Our data suggest that the replacement of large tracts of diverse wetlands with monocultures of this highly productive macrophyte could alter the net radiative forcing of wetlands at a regional scale, given that soil methane emissions were at least three-times greater from Typha-invaded than native Soils collected from Typha-invaded stands had greather methane production potential than native wet meadows in three Midwestern wetlands (mean ± 1 SE; n = 5). ...
Article
Wetland invasion by monotypic dominant plants can alter the physicochemical and biological properties of soils that affect methane emissions, a potent greenhouse gas. We examined the effects of Typha × glauca invasion on soil methane using laboratory incubation and controlled mesocosm experiments. Typha-invaded soils collected from three Midwestern (USA) wetlands had greater methane production potential during laboratory incubation than soils dominated by native wet meadow vegetation. Ten years post-invasion of native plant-dominated mesocosms, Typha increased methane emissions at least three-fold (native: 15.0 ± 10.5 mg CH4-C m⁻² h⁻¹, median: 6.1 mg CH4-C m⁻² h⁻¹; Typha: mean: 45.9 ± 16.7 mg CH4-C m⁻² h⁻¹, median: 26.8 mg CH4-C m⁻² h⁻¹) under high (+10 cm) water levels, though methane emissions were negligible under low (–10 cm) water levels. Methane emissions were positively correlated with soil carbon, nitrogen, and aboveground biomass, all of which were greater in Typha-invaded mesocosms. Together, our data suggest that replacement of large tracts of native wetlands throughout eastern North America with monocultures of invasive Typha could alter regional methane emissions.
... Specifically, invasive species pose a significant threat to coastal wetlands, as they can grow in dense, monolithic stands, outcompeting native species and altering wetland vegetation structure (Marks et al. 1994;Zedler and Kercher 2004). Rapid expansion of invasive species such as Phragmites australis and Typha x glauca is occurring across North America (Tulbure et al. 2007). The Laurentian Great Lakes and their associated wetlands and waterways are at increasing risk of invasion by these species due to high exposure to conditions that promote successful invasion such as anthropogenic nutrient applications to the landscape, typically as fertilizer and other nonpoint sources, and land use change from natural to agricultural or urban landscapes (Danz et al. 2007;King et al. 2007). ...
... The transects nearest a highly developed area, resulted in the highest occurrence of Phragmites within the study region (King et al. 2007). Mixed models have also been used to explore relationships between the change in Phragmites cover and various wetland characteristics at specific sites (Tulbure et al. 2007). ...
Article
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ContextFreshwater coastal wetlands provide numerous ecosystem services, including habitat, nutrient uptake, coastal stabilization, and aesthetic value, but the integrity of these ecosystems is threatened by invasion of non-native competitors. Invasive species, such as Phragmites and Typha, are a concern in these wetlands, as they can dominate and outcompete native species.Objectives This work sets out to understand the conditions that allow invasive species to dominate. This will allow for better management of landscapes and wetlands.Methods We bring together two datasets to relate landscape conditions to coastal wetland invasion: (1) a spatially explicit map of nutrient inputs (SENSEmap) across the US Great Lakes Basin, and (2) a satellite land use map that includes explicit classifications of wetlands. Using machine learning algorithms, we quantified correlations between wetland plant invasion along the coastline to nutrient loads (both N and P) and other landscape scale variables (hydraulic conductivity, slope, imperviousness, land use, and land cover) across multiple influence zones.ResultsWe find that high invasion is typically associated with nitrogen loading above 118 kg/ha/year within the watersheds of the invaded wetlands. Forest cover of < 27% is associated with high invasion. Conversely, nearshore slope of > 2.6% and phosphorus loads < 2.8 kg/ha/year are associated with low invasion. Through N:P ratios, phosphorus was further identified as important. Overall, areas more anthropogenically impacted were more associated with invasion.Conclusions We conclude that high nitrogen and low forest cover are correlated with invasion. These conclusions will inform management, as well as future efforts to identify linkages between landscapes and coastal invasion.
... The study area for this research included the U.S. coastline of the five North American Great Lakes and . Sources of disturbance to these wetlands in the latter half of the twentieth century and the beginning of the twenty-first century included fluctuating lake levels (Albert 2003;Gronewold et al. 2013), invasion by exotic plants (Trebitz and Taylor 2007;Tulbure et al. 2007;Tulbure and Johnston 2010), and changes in adjacent land use (Wolter et al. 2006). These disturbances have been shown to alter the structure and composition of communities of plants, diatoms, macroinvertebrates, amphibians, fishes, and birds living in the marshes (Brazner 1997;Albert 2003;Brazner et al. 2007;Trebitz et al. 2009). ...
... Management techniques successfully used for black terns include herbicide application (Linz et al. 1994) or rotating marshes through a cycle of drawdown and reflooding where hydrologic management is an option (Shuford 1999). In the Great Lakes, managers should focus especially on restoring native emergent vegetation and containing or eradicating invasive plants such as hybrid cattail (Typha 9 glauca) and the invasive genotype of common reed (Phragmites australis) that rapidly form dense stands once established (Tulbure et al. 2007;Mitchell et al. 2011). Predicted drops in Great Lakes lake levels due to climate change (Angel and Kunkel 2010) are likely to facilitate further invasion of coastal wetlands by both hybrid cattail and invasive common reed (Lishawa et al. 2010;Tulbure and Johnston 2010). ...
Article
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Breeding colonies of black terns (Chlidonias niger) have become increasingly rare in U.S. Great Lakes coastal wetlands since the mid-twentieth century, with an almost 90% decline in the number of active colony sites since 1991. Although the specific causes of this wetland species’ decline are unknown, habitat loss and degradation are thought to be a major barrier to conservation. Using data from the Great Lakes Colonial Waterbird Survey, we took a unique regional and historical approach to investigate the relationship between black tern colony site abandonment and a suite of local and landscape-scale habitat features in U.S. Great Lakes coastal wetlands. We employed logistic regression models and a combination of stepwise selection procedures to identify the best predictive model for black tern colony abandonment. According to the selected model, breeding colonies with fewer nests were more likely to be abandoned over the following decadal observation period than breeding colonies with more nests. Colony sites were also more likely to be abandoned when vegetation within the wetland shifted towards larger, denser clusters. We performed a simulation study that showed that failing to account for association between observations from the same site affected model selection results, but that cross-validation error for the selected model remained low unless site effects were very strong. Results of this study suggest that focus on protection of sites harboring large numbers of black terns and vegetation management will help limit further colony abandonments.
... Gronewold and Stow, 2014) will affect invasion risk. In areas subjected to lower water levels, the consequent increase in exposed shoreline is expected to favor invasive macrophytes (Tulbure and Johnston, 2010;Tulbure et al., 2007). ...
Article
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No other freshwater system contains as many non-native species or has been invaded as frequently as the Great Lakes-St. Lawrence River basin. Over 180 non-native species have become established in the basin within the past two centuries. Collectively, these invasions have altered biodiversity, habitat structure, productivity, water quality, contaminant cycling and ecosystem services. The composition and rate of discovery of invaders are correlated with changes in dominant vectors, such as transoceanic shipping. We review the invasion history of the basin and identify future invasion threats by considering trends and potential scenarios in changing vectors and pathways. Whereas most non-native species discovered since the opening of the St. Lawrence Seaway in 1959 were attributable to ballast water discharge from transoceanic vessels, recent regulations have apparently reduced the threat of this vector. Nevertheless, non-native species may continue to be introduced through poorly-regulated vectors, particularly those associated with trade in live organisms. The spread and impact of current and future invaders are expected to be exacerbated by interactions with other anthropogenic stressors that are increasing in frequency and spatial extent. Most notably, the continued warming of surface waters of the Great Lakes basin will lift thermal barriers to invasions by warm-water taxa. Contrary to any perception that the “worst is over” (i.e. most harmful invasions have already occurred), the basin remains vulnerable to further ecological and economic disruptions from non-native species.
... Introduced, non-native Phragmites australis ssp. australis (hereafter Phragmites) has rapidly spread throughout the lower Great Lakes and St. Lawrence River in the last 20 years (Wilcox et al. 2003;Catling and Carbyn 2006;Tulbure et al. 2007). At low densities, interspersed Phragmites provides excellent habitat structure for wildlife (Cross and Fleming 1989), while at higher densities, it becomes an ecosystem modifier, altering soil properties, hydrology, nutrient cycling, and temperature (Windham and Lathrop 1999;Meyerson et al. 2000;Warren et al. 2001). ...
Article
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Non-native Phragmites australis ssp. australis (hereafter Phragmites) is well-established and spreading at the Long Point Peninsula. It is threatening biodiversity, making it a high priority for management. Detailed studies on rates of spread and growth patterns at the landscape-scale are needed for better informed management efforts. In this study, the spatial characteristics of Phragmites in Big Creek and Long Point National Wildlife Areas were quantified using airphoto delineations from 1945 to 2013. Three management units differing in size, habitat, and source of anthropogenic disturbance were compared. Boosted regression tree models were employed to predict future distributions to 2022. Dramatic increases in Phragmites cover (14–37% annually) far exceeding previous detections were measured starting in the mid-1990s. Dispersal was an important factor (14–66%) for spread. Expansion rates were highly variable and increased with longer perimeters. Major predicting factors were proximity to existing stands, vegetation class, and elevation. Vulnerable habitats were characterized as low lying, low sloped, marsh and shallow aquatic vegetation, and areas near water and development. Under static water-levels, Phragmites is predicted to continue spreading at near current rates to 2022 and may begin to encroach into drier habitats.
... s stands that tolerate seasonal water draw-downs and inundation (Weller 1975;van der Valk and Davis 1978). Likewise, the native Phragmites subspecies (Phragmites australis americanus) can be found in isolated locations in North America, but again almost all Phragmites is a nonnative subspecies (Phragmites australis australis) originating in Europe (Tulbure et at. 2007). The aggressive habits of both the cattail hybrid and the nonnative Phragmites allow them to outcompete and displace native plants important to animals dependent on wetlands for survival and reproduction . Otis and Kilburn (1988) found that the main predictor of the severity of blackbird damage to sunflower is the presence or absence of ...
... The Typha, which started off covering half of the wetland area, clearly struggled in that environment compared to the Phragmites that colonised the entire wetland over the 9 year period. This would seem to corroborate studies in many places throughout the world that have shown that Phragmites acts as an invasive species due to competitive advantages due to high rates of primary productivity (Tulbure et al., 2007;Brisson et al., 2010). ...
Article
The accumulation of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) in the sediment and plants growing in a constructed wetland used to treat highway runoff in Ireland has been quantified after 6 and 9 year periods of operation. The spatial distribution of the metals' deposition showed strong evidence of flow channelling through the wetland with a strong correlation between the spatial accumulation, particularly for Cr, Cu, Pb and Zn with most of these metals deposited towards the front of the wetland in the sediment. Highest accumulation in the wetland was for Zn, followed by Cu, Pb, Cr, Ni and Cd. The study also quantified that an almost negligible mass of metals had accumulated in the vegetation compared to the sediment. However, an apparent increase in metal accumulation with time may be linked to the cumulative annual production and deposition of organic matter, indicating the importance of the vegetation as an integral part of the treatment process. Based on the measured accumulation and projected runoff loads over the 9 year period, the apparent removal efficiencies were 5% (Cd), 60% (Cu), 31% (Pb) and 86% (Zn). This equates to accumulation rates of 0.1 (Cd), 15.6 (Cu), 11.6 (Pb) and 88.3 (Zn) g per m² highway drained per year.
... Indeed, the large wetland invaders we simulated, such as Phragmites australis subsp. australis and Typha # glauca (whose M max is comparable to the largest invader we modeled), may be able to establish dense monocultures in coastal wetlands of the Laurentian Great Lakes only during periods of low water when newly exposed bare soil is available for colonization (Tulbure et al. 2007;Wilcox 2012). However, our results also suggest that such large species can successfully invade and dominate even undisturbed native vegetation where nitrogen inflows are high enough. ...
Article
Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better, we found that invader success and competitive ability are unimodal functions of maximum potential size, such that plants that are too large (or too small) are disproportionately suppressed by competition. Optimal size increases with nitrogen supply, even when plants compete for nitrogen only in a size-symmetric manner, although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in large differences in plant invasion success and the influence of competition along productivity gradients.
... Although largely beneficial, cattails can also invade wetlands to the extent that they deleteriously impact biodiversity and alter nutrient pools, biogeochemical cycles, and bacterial communities (Tulbure et al., 2007;Geddes et al., 2014;Lishawa et al., 2014). Invasive cattails may be introduced, hybrid, or native species that monopolize sites, most commonly in response to either natural or anthropogenic perturbations (e.g. ...
Article
Cattails (Typha spp.) are essential components of wetland around the world, although they can also be problematic invaders. In some regions of North America, T. latifolia and T. angustifolia hybridize to produce T. x glauca, which is invading and dominating wetlands around the Laurentian Great Lakes. However, in other regions such as China and the maritime provinces of Canada, hybrids are either non-existent or maintained at very low frequencies, and cattails are not considered invasive. Little is known about cattail hybrids in Europe. We used microsatellite markers to characterize T. latifolia, T. angustifolia, T. laxmannii, and T. domingensis sampled from 63 sites across nine European countries. Hybrids were very uncommon ( < 2% of all sampled plants), and resulted from crosses involving two of T. latifolia, T. angustifolia and T. domingensis. Infrequent hybridization may partly explain why Typha does not dominate European wetlands. However, we identified two distinct genetic clusters within T. angustifolia, broadly corresponding to eastern and western Europe. In addition, our T. laxmannii samples were from countries where it is considered alien, and populations show a high degree of genetic differentiation that is consistent with independent introductions. Managers should continue to monitor range expansions of Typha spp. in Europe, partly because novel interactions among species and lineages may increase the likelihood of future hybridization.
... Phragmites australis was also the predominant emergent species in many areas along the lower Pearl River, but it infrequently occurred in other Mississippi sites. Both P. australis and T. domingensis tend to colonize into areas that have been disturbed or are geologically dynamic (Tulbure et al. 2007). Myriophyllum spicatum is often considered an invasive SAV in Louisiana and Alabama, however, it appeared to be rare in the Mississippi coastal waters sampled during the period of the field surveys (Cho et al. 2012). ...
Article
Habitat attributes of submerged aquatic vegetation and floating-leaved aquatic vegetation were analyzed from survey data collected in estuaries and coastal river systems of Mississippi and Mobile Bay, Alabama. The objectives were to: locate aquatic plant beds along tidally influenced areas and characterize landscape parameters of the sites; group the plant species into a manageable number of logical clusters; and characterize the landscape attributes indicative of the plant communities through Classification and Regression Tree (CART) analysis. Based on the cluster analyses, aquatic vegetation was categorized into three groups: (1) downstream estuarine/saline group, (2) brackish tolerant freshwater species group, and (3) upstream freshwater only group. Landscape features used for habitat characterization and plant classification were defined by long-term environmental conditions which would shape plant communities, rather than water quality parameters, such as water transparency and salinity, that exhibit higher variability and reflect the discrete conditions at time of sampling. The CART results suggest that salinity and “energy” (relative exposure to waves/currents) are the two most important abiotic factors that structure plant communities in the river deltas studied. https://muse.jhu.edu/article/641171/pdf
... australis cover expanded after a water level drop (Tulbure et al., 2007;Whyte et al., 2008). In the late 1980s introduced P. australis was not a dominant plant species in the Great Lakesat this time Typha was the dominant plant species and the main concern towards Great Lake biodiversity (Keddy and Reznicek, 1986). ...
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nvasive Phragmites australis threatens the integrity of essential bird habitat in coastal marshes. Located on the north shore of Lake Erie, Long Point, Ontario provides habitat to thousands of breeding and migrating birds, including marsh-nesting species in decline around the Great Lakes. Invasive P. australis has been colonizing these marshes since the late 1990s, when concerns prompted a survey of birds in invaded wetlands (2001-2002). My work evaluates birds in these wetlands after over a decade of P. australis expansion, comparing birds among P. australis and the vegetation communities it is displacing: cattail marsh, meadow marsh, and open-water marsh. I also examined bird community composition and functional traits to better capture the effects of P. australis invasion. I observed substantial changes since the 2001-2002 study was conducted. In 2015, total bird abundance was lower in P. australis than cattail marsh, with little difference in bird species richness among vegetation types. Bird community composition was distinct among all four vegetation types; however, P. australis supported a subset of bird species within cattail and meadow marsh habitat, rather than novel bird species. Phragmites habitat excludes many marsh-nesting species and provides habitat for shrub-nesting, foliage gleaner bird species. Marsh-nesters of conservation concern are restricted to remaining cattail and meadow marsh, and open-water habitat. My work indicates that the full effects of P. australis invasion may exhibit a lag time, and that community composition and functional traits should be considered when evaluating the effects of a biological invasion.
... High levels of mortality in these low-nutrient conditions create a large disturbance that allows Typha to re-invade and rapidly increase. In the field, Typha often rapidly colonizes disturbed areas (Tulbure et al. 2007) and may even require such disturbances for establishment since it competes poorly with well-established stands of native vegetation in (DGE, unpublished data). In high N environments with a dense canopy, herbicide does not create a completely open canopy, which may limit the ability of Typha to reinvade and make herbicide more effective. ...
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Wetlands occupy a position in the landscape that makes them vulnerable to the effects of current land use and the legacies of past land use. Many wetlands in agricultural regions like the North American Midwest are strongly affected by elevated nutrient inputs as well as high rates of invasion by the hybrid cattail Typha × glauca. These two stressors also exacerbate each other: increased nutrients increase invasion success, and invasions increase nutrient retention and nutrient loads in the wetland. This interaction could create a positive feedback that would inhibit efforts to manage and control invasions, but little is known about the effects of past or present nutrient inputs on wetland invasive plant management. We augmented a previously-published community-ecosystem model (Mondrian) to simulate the most common invasive plant management tools: burning, mowing, and herbicide application. We then simulated different management strategies and 3 different durations in low and high nutrient input conditions, and found that the most effective management strategy and duration depends strongly on the amount of nutrients entering the wetland. In high-nutrient wetlands where invasions were most successful, a combination of herbicide and fire was most effective at reducing invasion. However, in low-nutrient wetlands this approach did little to reduce invasion. A longer treatment duration (6 years) was generally better than a 1-year treatment in high-nutrient wetlands, but was generally worse than the 1-year treatment in low-nutrient wetlands. At the ecosystem level, we found that management effects were relatively modest: there was little effect of management on ecosystem C storage, and while some management strategies decreased wetland nitrogen retention, this effect was transient and disappeared shortly after management ceased. Our results suggest that considering nutrient inputs in invaded wetlands can inform and improve management, and reducing nutrient inputs is an important component of an effective management strategy.
... Since European settlement, a significant portion of the naturally occurring Great Lakes coastal ecosystem area has been lost (N50%), and coastlines have lost over 95% of their wetland habitat in some areas (Cwikiel, 1998;Krieger, 1992). Remaining wetlands have been further subjected to increased levels of fragmentation, degradation, and invasion of exotic plant species, greatly reducing the biodiversity and overall habitat quality of these valuable ecosystems Tulbure et al., 2007;Uzarski et al., 2009). In addition to wetlands, open water and nearshore embayment habitats (Peterson et al., 2007), rivers , and river mouths (Larson et al., 2013) of the Great Lakes have been impacted by surrounding land-use. ...
Article
The Laurentian Great Lakes of North America have been a focus of environmental and ecosystem research since the Great Lakes Water Quality Agreement in 1972. This study provides a review of scientific literature directed at the assessment of Laurentian Great Lakes coastal ecosystems. Our aim was to understand the methods employed to quantify disturbance and ecosystem quality within Laurentian Great Lakes coastal ecosystems within the last 20 years. We focused specifically on evidence of multidisciplinary articles, in authorship or types of assessment parameters used. We sought to uncover: 1) where Laurentian Great Lakes coastal ecosystems are investigated, 2) how patterns in the disciplines of researchers have shifted over time, 3) how measured parameters differed among disciplines, and 4) which parameters were used most often. Results indicate research was conducted almost evenly across the five Laurentian Great Lakes and that publication of coastal ecosystems studies increased dramatically ten years after the first State of the Great Lakes Ecosystem Conference in 1994. Research authored by environmental scientists and by multiple disciplines (multidisciplinary) have become more prevalent since 2003. This study supports the likelihood that communication and knowledge-sharing is happening between disciplines on some level. Multidisciplinary or environmental science articles were the most inclusive of parameters from different disciplines, but every discipline seemed to include chemical parameters less often than biota, physical, and spatial parameters. There is a need for an increased understanding of minor nutrient, toxin, and heavy metal impacts and use of spatial metrics in Laurentian Great Lakes coastal ecosystems.
... Typha can expand rapidly (e.g., up to 4-m in clone diameter per year; Boers and Zedler, 2008) in response to nutrient enrichment (Woo and Zedler, 2002) and altered hydroperiods (Hall and Zedler, 2010;Lishawa et al., 2010), often resulting in large monotypic stands. The spread of dense Typha clones throughout the Great Lakes region (Galatowitsch et al., 1999;Lishawa et al., 2010;Tulbure et al., 2007) has altered coastal wetland ecosystems by increasing plant biomass and litter production, decreasing native plant species diversity (Frieswyk and Zedler, 2006;Mitchell et al., 2011;Tuchman et al., 2009), altering nutrient cycling regimes (Farrer and Goldberg, 2009;Larkin et al., 2012;Lishawa et al., 2014), decreasing light penetration (Lishawa et al., 2015), and buffering temperatures . ...
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Aquatic macroinvertebrates are a critical component of wetland nutrient cycling and food webs, with many fish and wildlife species depending upon them as food resources; but little is known about how invasion by dominant macrophytes may alter community dynamics. We examined the impacts of Typha invasion on aquatic macroinvertebrate communities in three northern Great Lakes coastal wetlands by comparing community composition between stands of native emergent marsh and those dominated by invasive Typha. Typha invaded zones were associated with shallower and cooler water than native emergent zones, and we detected decreased aquatic macroinvertebrate density and biomass in invaded zones. After accounting for the positive effect of plant species richness on macroinvertebrate abundance, we observed Typha invaded coastal zones had less total macroinvertebrate and insect biomass than native zones across all levels of plant richness. Our results suggest that Typha invasion reduces habitat quality for aquatic macroinvertebrates by homogenizing structural diversity and reducing water temperatures, which in turn may negatively impact predatory organisms by decreasing food resources. We recommend experimental tests of Typha management treatments to identify techniques that may promote structurally diverse and biologically rich Great Lakes coastal wetlands.
... The weak influence from detection and misidentification on Mean C values in this study suggests that actual changes in species composition would be the more important of these possible causes (e.g., real extinctions or colonizations). To this point, several authors have warned that shortterm species composition changes due to natural disturbances could make FQA measurements unstable or useable [30,55]. Or, at a minimum, Mack et al. [11] and Wilson and Bayley [56] recommend not sampling a community if an extreme weather event such as drought or flooding has occurred because such samples might not be representative of the site over the longterm. ...
Article
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Floristic Quality Assessment (FQA) is increasingly influential for making land management decisions, for directing conservation policy, and for research. But, the basic ecological properties and limitations of its metrics are ill defined and not well understood-especially those related to sample methods and scale. Nested plot data from a remnant tallgrass prairie sampled annually over a 12-year period, were used to investigate FQA properties associated with species detection rates, species misidentification rates, sample year, and sample grain/area. Plot size had no apparent effect on Mean C (an area's average Floristic Quality level), nor did species detection levels above 65% detection. Simulated species misidentifications only affected Mean C values at greater than 10% in large plots, when the replaced species were randomly drawn from the broader county-wide species pool. Finally, FQA values were stable over the 12-year study, meaning that there was no evidence that the metrics exhibit year effects. The FQA metric Mean C is demonstrated to be robust to varied sample methodologies related to sample intensity (plot size, species detection rate), as well as sample year. These results will make FQA measures even more appealing for informing land-use decisions, policy, and research for two reasons: 1) The sampling effort needed to generate accurate and consistent site assessments with FQA measures is shown to be far lower than what has previously been assumed, and 2) the stable properties and consistent performance of metrics with respect to sample methods will allow for a remarkable level of comparability of FQA values from different sites and datasets compared to other commonly used ecological metrics.
... However, two of the species identified, ). Phragmites specifically is expanding throughout the Great Lakes (Tulbure et al., 2007; Mazur et al., 2014) and in some instances has been found to negatively influence fish and marsh bird populations (Able, 2003; Hunter, 2006; Whyte et al., 2015). Since Phragmites is an emergent species, this line of discussion likely falls outside of the scope of the current evaluation of the SAV BUI. ...
... North American expansion of cattails over the past 100 years (Grace and Harrison 1986;Galatowitsch et al. 1999) has been driven by a combination of environmental (e.g., Wilcox et al. 1985;Woo and Zedler 2002) and evolutionary forces Ball and Freeland 2013). Typha × glauca is considered the most invasive North American Typha species (Smith 1987;Galatowitsch et al. 1999), although some consider T. angustifolia equally invasive (Tulbure et al. 2007). Typha × glauca is reportedly more eff ective at supplanting native vegetation (Galatowitsch et al. 1999;Woo and Zedler 2002;Boers et al. 2007) and inhibits germination of native species once established (Frieswyk and Zedler 2006). ...
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Hybridization of plants occurs when two species from the same or different genera mate and can successfully produce viable seeds. Hybridization of plants can increase genetic diversity, but it can also result in aggressive taxa that can displace native species and decrease wetland plant biodiversity. Here we identify two cattail species, Typha latifolia L. and T. angustifolia L., and hybrids of these two species referred to as T. x glauca Godr. using molecular markers called microsatellites, since morphological characteristics are not reliable indicators for identifying cattail taxa. The importance of cattail hybridization is that it has facilitated cattail spread in various wetlands of North America. From 2004 to 2012 we evaluated whether hybridization of cattails was occurring in seven Great Lakes national parks and two other national parks. We present results for Apostle Islands National Lakeshore, Cuyahoga Valley National Park, Indiana Dunes National Lakeshore, Pictured Rocks National Lakeshore, St. Croix National Scenic Riverway, Sleeping Bear Dunes National Lakeshore, and Voyageurs National Park. All parks except Pictured Rocks included hybrid taxa. The technique holds promise for cattail taxonomic identification for wetland managers. Cattail management methods are also described.
... Hybrid cattail (Typha angustifolia 9 Typha latifolia = T. 9 glauca; hereafter Typha) is one of the most problematic wetland invaders throughout eastern North America and the Great Lakes region (Freeland et al. 2013;Frieswyk and Zedler 2007;Lishawa et al. 2010;Tuchman et al. 2009;Tulbure et al. 2007;Vaccaro et al. 2009). It rapidly expands in response to nutrient enrichment (Woo and Zedler 2002) and hydrologic changes (Boers and Zedler 2008;Hall and Zedler 2010;Lishawa et al. 2010), reducing waterfowl habitat (Leitch et al. 1997) and plant diversity (Frieswyk and Zedler 2006;Tuchman et al. 2009), as well as altering ecosystem functions such as methane emissions (Lawrence et al. unpublished data) and denitrification potential (Lishawa et al. 2014). ...
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Invasive wetland plants are the primary targets of wetland management to promote native communities and wildlife habitat, but little is known about how commonly implemented restoration techniques influence nutrient cycling. We tested how experimental mowing, herbicide application, and biomass harvest (i.e., removal of aboveground biomass) treatments of Typha-invaded mesocosms altered porewater nutrient (NO3−, NH4+, PO 4−3) concentration and supply rate, vegetation response, and light penetration to the soil surface. We found that while herbicide application eliminated the target species, it also reduced native plant density and biomass, as well as increased porewater nutrient concentration (PO 4−3, NO3−) and supply rates (N, P, K) up to a year after treatments were implemented. Because herbicide application promotes nutrient enrichment, it may increase the likelihood of reinvasion by problematic wetland invaders, as well as cause eutrophication and deleterious algal blooms in adjacent aquatic systems. Our data suggest that biomass harvest should be considered by managers aiming to reduce Typha abundance without eradicating native diversity, avoid nutrient leaching, as well as possibly utilizing biomass for bioenergy.
... This haplotype M has become very abundant in coastal tidal marshes (Rice, Rooth & Stevenson 2000;Warren et al. 2001;Philipp & Field 2005;Chambers et al. 2008) and, more recently, in freshwater wetlands of the Great Lakes -St. Lawrence River system (Wilcox et al. 2003;Hudon, Gagnon & Jean 2005;Trebitz & Taylor 2007;Tulbure, Johnston & Auger 2007). The plant has used road drainage ditches for spreading inland (Jodoin et al. 2008;Lelong, Lavoie & Th eriault 2009;Brisson, de Blois & Lavoie 2010). ...
Article
1.Knowing the relative contribution of vegetative propagation and sexual reproduction to the dispersal and establishment of exotic plants is crucial for devising efficient control strategies. This is particularly true for the common reed (Phragmites australis), one of the most invasive species in North America.2.For the first time we combined in situ field observations and genetic evidence, based on two genotyping techniques, i.e., microsatellite markers (SSR) and genotyping-by-sequencing (GBS), to determine the propagation strategies of this invader at its northern distribution limit in North America, and especially in roadside ditches.3.Field observations revealed that, in a region where the common reed is already abundant, both seeds and plant fragments contributed to the establishment of new populations. Newly established individuals originated mostly (84%) from seeds rather than fragments, but a larger proportion of individuals originating from fragments survived the second year compared to seedlings.4.High genetic diversity among marsh and roadside common reed stands indicated the prime role of sexual reproduction for dispersal. The vast majority of genotypes were found in only one stand; such high genetic variability can only be explained by sexual reproduction. Half the surveyed stands comprised a single clone, suggesting that local expansion mainly occurred vegetatively. As the small proportion of SSR genotypes initially thought to be common between distant stands proved to be distinct (as revealed by GBS data), it is likely that all the stands examined were initially founded by genetically distinct individuals.5.Synthesis. Our study suggests that long-distance dispersal by seeds is important for the common reed, in marshes and roadsides, while both seeds and plant fragments contribute to short-distance dispersal along roads, at least in regions where the species is already abundant. The success of this invader in North America seems to be attributable to a reproduction strategy combining the advantages of sexuality with those of vegetative propagation. Moreover, this study shows that the GBS approach strongly reduces uncertainties associated with the use of a limited number of markers. This approach is especially valuable for ecologists dealing with an ever increasing number of invaders, of which few have identified microsatellite markers.This article is protected by copyright. All rights reserved.
... For example, it seems that the North American native lineage is more sensitive to drought in some regions, such as the southwestern United States, where it is often associated with small streams and springs, which are sensitive to small changes in water availability (Meyerson et al., 2010a;Kettenring and Mock, 2012;. In contrast, shortterm drought that leads to temporary drawdowns may benefit colonization of the NAint M lineage by fostering seedling recruitment (Alvarez et al., 2005;Tulbure et al., 2007;Whyte et al., 2008;Kettenring et al., 2015Kettenring et al., , 2016. These studies serve as examples for using P. australis as model to study, whether physiologically similar responses to different global change factors result from similar adaptations or are independent of the plants' phylogeographic origin. ...
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Phragmites australis is a cosmopolitan grass and often the dominant species in the ecosystems it inhabits. Due to high intraspecific diversity and phenotypic plasticity, P. australis has an extensive ecological amplitude and a great capacity to acclimate to adverse environmental conditions; it can therefore offer valuable insights into plant responses to global change. Here we review the ecology and ecophysiology of prominent P. australis lineages and their responses to multiple forms of global change. Key findings of our review are that: (1) P. australis lineages are well-adapted to regions of their phylogeographic origin and therefore respond differently to changes in climatic conditions such as temperature or atmospheric CO2; (2) each lineage consists of populations that may occur in geographically different habitats and contain multiple genotypes; (3) the phenotypic plasticity of functional and fitness-related traits of a genotype determine the responses to global change factors; (4) genotypes with high plasticity to environmental drivers may acclimate or even vastly expand their ranges, genotypes of medium plasticity must acclimate or experience range-shifts, and those with low plasticity may face local extinction; (5) responses to ancillary types of global change, like shifting levels of soil salinity, flooding, and drought, are not consistent within lineages and depend on adaptation of individual genotypes. These patterns suggest that the diverse lineages of P. australis will undergo intense selective pressure in the face of global change such that the distributions and interactions of co-occurring lineages, as well as those of genotypes within-lineages, are very likely to be altered. We propose that the strong latitudinal clines within and between P. australis lineages can be a useful tool for predicting plant responses to climate change in general and present a conceptual framework for using P. australis lineages to predict plant responses to global change and its consequences.
... Furthermore, the annual erosion rate in the North Unit of IBSP is 3 m/yr, which indicates that shoreline erosion is a chronic problem in this region. Wetlands can recolonize emergent coastlines, but the emergent wetlands are drowned and returned to open water during high lake level periods 45 . Given the short periodicity of lake level fluctuations in the Great Lakes (~30 years) 30 , it is unlikely that wetlands will be able to fully recover the carbon stock and area lost to geomorphic change during high lake levels. ...
Article
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Shoreline erosion can transition freshwater coastal wetlands from carbon sinks to carbon sources. No studies have explored the impacts of coastal geomorphic processes on freshwater wetland carbon budgets. To do so, we modified a saltmarsh carbon budget model for application in freshwater coastal wetlands. We validated the model with data from a shoreline wetland in the Laurentian Great Lakes. The model generates the carbon budget by differencing carbon export and carbon storage. The inputs for carbon storage are the carbon inventory and maximum wetland age. Inputs for carbon export include erosion rates and overwash extent. The model demonstrates that the wetland examined in this study transitioned to a source of carbon during periods of erosion. In fact, the net carbon export between 2015 and 2018 was 10% of the wetland’s original carbon stock. This study indicates that geomorphic change can dictate whether and how freshwater coastal wetlands serve as sources or sinks for terrestrial carbon, and that carbon stocks can fluctuate on a geologically rapid timescale. We recommend that such geomorphic processes be considered when developing carbon budgets for these marginal environments. Furthermore, the carbon budget model refined in this study can be used to prioritize wetlands in land management and conservation efforts.
... Plant-mediated methane transport Grace and Harrison 1986), and root to shoot ratios typically 1 g g −1 d.wt under ambient nutrient levels (Li et al. 2010). Cattail has invasive traits and is common in restored and natural wetlands where it forms dense monostands often outcompeting other species (Fennessy et al. 1994;Tulbure et al. 2007;Cronk and Fennessy 2016). Nelumbo lutea (Willd.) ...
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Methane flux from freshwater mineral‐soil (FWMS) wetlands and its variability among sites is largely modulated by plant‐mediated transport. However, plant‐mediated transport processes are rarely resolved in land surface models and are poorly parametrized for plants commonly found in FWMS wetlands. Here, relationships between methane flux and CO2 uptake, as well as plant conductance of methane were evaluated for three plant species and two characteristic functional types: emergent (narrow‐leaved cattail) and floating‐leaved (American lotus and water lily). We found significant but contrasting correlations between methane flux and CO2 uptake in cattails (r2 = 0.51, slope = −0.16, during morning) and water lily (r2 = 0.32, slope = 0.064, after midday). This relationship was not significant in American lotus, showing that stomata regulation of methane fluxes is species‐specific and not generalizable across the floating‐leaved plant functional type. Conductance of methane per leaf area showed distinct seasonal dynamics across species. Conductance was similar among the floating‐leaved species (6.2 × 10−3 m d−1 in lotus and 7.2 × 10−3 m d−1 in water lily) and higher than conductance in the emergent species (2.7 × 10−3 m d−1). Our results provide direct observations of plant conductance rates and identify the vegetation parameters (leaf area, stomatal conductance) that modify them. Our results further suggest that models of methane emissions from FWMS should parameterize plant‐mediated transport in different plant functional types, scaled by leaf area and with variable seasonal phenological dynamics, and consider possible species‐specific mechanisms that control methane transport through plants.
... Thus, while our TLMM model deals primarily with the outright loss of marshes that occurs with the removal of flood pulses, it is also important to consider a secondary effect, that reduced flood pulses will also change the species composition of the remaining marshes. Compositional changes may be more problematic when clonal invasive species such as Phragmites australis or Typha angustifolia are present (Tulbure et al. 2007;). ...
Article
Vast areas of wetland occur on shorelines of ponds, lakes, and rivers. These wetlands are divided into vegetation zones, including aquatic vegetation, marsh, and swamp. Here, we provide a simple, mechanistic, and non-equilibrium model that explains the occurrence of marsh as a function of past flood pulses. Marshes are sandwiched between two limits, both of which fluctuate with time. The lower limit is set by the tolerance of marsh plants to continuous flooding. The upper limit is set by competion with woody plants, which are killed by extreme high water events. The twin limit marsh model (TLMM) requires long-term water-level records and two biological inputs: duration of flooding required to drown marsh plants (f) and the duration of dewatering required for woody plants to reinvade once water levels drop (s). In the temperate zone, we suggest that f is ~4 yr and s is ~30 yr. We illustrate the model for the marshes of Lakes Erie and Ontario. High water years that kill woody plants, followed by low water years, produce large expanses of marsh. The regulation of lakes and rivers generally has negative effects on marsh area and diversity. The TLMM can be calibrated for other climates or ecoregions.
... In wetlands, for example, invasive emergent plants, such as common reed (P. australis), smooth cordgrass (Spartina alterniflora), and common cattail (Typha spp.), can spread rapidly across the wetland displacing other plant species and changing soil microbial communities along the way (Angeloni et al. 2006;Tulbure et al. 2007;Gao et al. 2019). Invasive spread of emergent plants can also reduce the availability of open water habitat for water birds and other wildlife, as well as reduce fish movement (Thouvenot et al. 2013). ...
Article
Wetlands are unique, highly biodiverse ecosystems of high conservation value that provide multiple ecosystem services to human society. However, the dynamic nature of wetlands creates abundant opportunities for the establishment and spread of invasive species, especially those well adapted to the current global prevalence of environmental change. Wetland invasibility is influenced by ongoing changes in climate and human land use (e.g., hydrologic modifications and eutrophication). Invasive species, in turn, can change the community composition and structure of the colonized wetlands through direct competition, predation, habitat alterations, hybridization, and pathogen transmission. Invaders can also alter ecosystem functioning, including hydrology, sedimentation, fire regimes, food webs, nutrient cycling, and succession. These changes in the biotic community and ecosystem functioning can affect human derived wetland services such as navigation, water distribution, and resource provision, as well as exaggerate problems related to human health. Although we currently possess diverse tools for managing individual species invasions, the current rate of global change may require creative approaches to achieve management success in the near future. Single-species or single-parameter approaches are unlikely to provide sustained biodiversity protection in this time of unprecedented environmental change, and hierarchical or multi-stressor approaches may become the new norm for managing wetland invasion.
... Due to its ability to survive under a wide range of conditions, this reed can be found in a variety of habitats, including dry or wet soil conditions, and freshwater or brackish aquatic habitats (Chambers et al., 1999;Sturtevant et al., 2019). Recently, Phragmites has spread prolifically along the Saint Lawrence River, throughout the Great Lakes region, and along major highway systems, which serve as major transport corridors in North America and facilitate substantial inland spreading (Hudon et al., 2005;Lelong et al., 2007;Tulbure et al., 2007;Jodoin et al., 2008). Given its prolific and hardy nature, it is important that land managers be able to locate stands of Phragmites, both while they are still relatively small as well as larger established stands, in order to control, eradicate, or prevent the spread of new or existing stands. ...
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Invasive species pose one of the greatest threats to global biodiversity. Early detection of invasive species is critical in order to prevent or manage their spread before they exceed the ability of land management groups to control them. Optical remote sensing has been established as a useful technology for the early detection and mapping of invasive vegetation populations. Through the use of airborne hyperspectral imagery (HSI), this study establishes a target detection methodology used to identify and map the invasive reed Phragmites australis subsp. australis within the entire extent of Îles-de-Boucherville National Park (Quebec, ON, Canada). We applied the Spectral Angle Mapper (SAM) target detection algorithm trained with a high accuracy GNSS ground truth data set to produce a park-wide map illustrating the extent of detected Phragmites . The total coverage of detected Phragmites was 26.74 ha (0.267 km ² ), which represents 3.28% of the total park area of 814 ha (8.14 km ² ). The inherent spatial uncertainty of the airborne HSI (∼2.25 m) was accounted for with uncertainty buffers, which, when included in the measurement of detected Phragmites , lead to a total area of 59.17 ha (0.591 km ² ), or 7.26% of the park. The overall accuracy of the Phragmites map was 84.28%, with a sensitivity of 76.32% and a specificity of 91.57%. Additionally, visual interpretation of the validation ground truth dataset was performed by 10 individuals, in order to compare their performance to that of the target detection algorithm. The overall accuracy of the visual interpretation was lower than the target detection (i.e., 69.18%, with a sensitivity of 59.21% and a specificity of 78.31%). Overall, this study is one of the first to utilize airborne HSI and target detection to map the extent of Phragmites over a moderately large extent. The uses and limitations of such an approach are established, and the methodology described here in detail could be adapted for future remote sensing studies of Phragmites or other vegetation species, native or invasive, at study sites around the world.
... For example, giant hogweed Heracleum mantegazzianum from the western Caucasus has invaded 14 different habitats (including spruce forests, mown meadows, grasslands, and urban sites) in the Czech Republic (Pyšek and Pyšek 1995). The common reed Phragmites australis has invaded native marshes, unvegetated mud flats, and tidal creeks in Canada and the United States (Tulbure et al. 2009;Mozdzer and Megonigal 2013). The exotic mangrove Rhizophora mangle has spread rapidly in vegetated coastal marshes and unvegetated sandy flats and drainage channels, transforming these habitats into heavily vegetated areas in Hawaii, USA, and Botany Bay, Australia (Mitchell and Adam 1989;Allen 1998). ...
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Exotic plants with wide ecological niches often invade multiple types of habitats, leading to homogenization of ecosystem structure and functions. How exotic plant invasions affect the structure and functions of benthic food webs in different habitats is poorly understood. We tested how Spartina alterniflora invasions affected benthic food webs in four contrasting types of habitat (Scirpus mariqueter marshes, Phragmites australis marshes, unvegetated tidal creeks, and bare tidal flats) in the Yangtze estuary. We examined distribution pattern of benthic macroinvertebrates, and documented the differences in basal resources of benthic food web by stable isotope analyses of δ13C and δ15N in different habitats. Our results showed that in unvegetated habitats, conversion of tidal creeks and bare tidal flats to exotic marshes following Spartina invasions significantly altered the functional composition of benthic food webs, which was driven partially by bottom‐up processes related to a consumer dietary shift from benthic organic matter to detritus (trophic effect) and by alteration in species composition related to habitat changes (nontrophic effect). In vegetated native habitats, while the replacement of native plants by Spartina consistently led to a shift in consumer diet from benthic organic matter to detritus, it did not significantly alter the functional composition of benthic food webs. These data suggested the relative importance of trophic and nontrophic effects of plant invasions on benthic food webs could vary with habitat structure (e.g., the presence of native vegetation). Our study provides new insights into the mechanisms underlying homogenization of ecosystem structure and functions by exotic plant invasions.
... Compared to aquatic invasive plant species, the influence of emergent invasives, such as common reed, narrow-leaved and hybrid cattail, purple loosestrife (Lythrum salicaria), and reed canary grass (Phalaris arundinacea), on ecosystem functioning has received greater research attention. Reduced plant diversity has been found with the expansion of common reed (Tulbure et al. 2007, Whyte et al. 2008, purple loosestrife (Thompson et al. 1987, IPBES 2018, reed canary grass (Houlahan andFindlay 2004, Perkins andWilson 2005), and invasive cattail (Lishawa et al. 2010(Lishawa et al. , 2015. Common reed captures detritus and sediment, which affected use of wetlands by fish and benthic invertebrates and raised soil surface levels Stevenson 2000, Rooth et al. 2003). ...
Technical Report
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European frog-bit (Hydrocharis morsus-ranae; EFB) is an invasive aquatic plant species that has quickly spread within Michigan, yet the detrimental effects to wetland ecosystems remain largely unknown. With funding provided by the Water Resources Division of the Michigan Department of Environment, Great Lakes, and Energy, the Michigan Natural Features Inventory worked with Central Michigan University as they developed an adaptive management plan for EFB. Our work focused on gathering and compiling EFB occurrence data, synthesizing information about the effects of EFB and other aquatic invasive plant species on native species and ecosystem functioning, identifying important knowledge gaps, and developing a research framework to address those information needs. We gathered and aggregated 8,214 records of known EFB status in the U.S. and Canada, with 3,916 unique occurrences being from Michigan. The limited information about the potential effects of EFB and other aquatic invasive plant species on native plants and animals and ecosystem processes was synthesized from available literature. Based on our literature search, we identified several important information needs regarding the impacts of EFB on wetlands: the effects of EFB on other organisms; effects of EFB on ecosystem processes; influence of EFB density and patch size on organisms and processes; interaction of EFB with other invasive species; conditions driving EFB occurrences; ecosystem resiliency to invasion; and effects of EFB to ecosystem services and human values. Five research objectives were proposed to address these knowledge gaps: 1) compare plant and animal communities between wetlands with and without EFB populations; 2) compare measures of ecosystem processes between wetlands with and without EFB populations; 3) examine associations between ecosystem variables and EFB density and patch size; 4) assess if EFB populations interfere with recreational use of wetlands; and 5) evaluate if EFB is affecting ecosystem services. We suggested several elements to strengthen study designs and increase the likelihood of detecting ecological patterns. Study designs should include reference sites representing naturally functioning wetlands as a comparison to wetlands containing EFB populations. The study areas should encompass the range of the invasion gradient (i.e., from well-established, high density to recent, low density sites) and types of wetlands containing EFB (e.g., coastal and inland; marshes, lakes, and ponds). Sampling should be replicated spatially (e.g., across EFB distribution in Michigan) and temporally (e.g., over multiple years) to the greatest extent possible to account for natural variation. We also recommend study designs that evaluate EFB effects to native species, ecological processes, ecosystem services, and human values concurrently. We suggested several measures of organismal communities and ecological functioning and associated sampling methodologies to address the proposed research objectives. Sampling of plant, macroinvertebrate, fish, herptile (frogs, toads, and turtles), and bird (waterfowl, waterbirds, and shorebirds) communities and indicators of ecological processes, such as water chemistry (e.g., DO, pH, nutrients), water movement (e.g., fluctuations, flow), and physical/structural variables (e.g., biomass, soils, light penetration), is recommended to understand potential impacts from EFB. Measuring species and processes across EFB density and size gradients may assist in determining if there are EFB population thresholds at which detrimental impacts to native species and normal ecosystem processes occur. Stakeholder engagement is needed to understand the effects of EFB on human values, such as recreational use. Finally, we recommended developing a conceptual model to describe the interaction of ecosystem processes, ecosystem services, human values, and EFB. New knowledge gained about alterations to processes associated with EFB could then be incorporated into the model to predict resulting changes to ecosystem services and human values.
... The four high-risk and weedy species Phragmites australis, Sparganium ramosum, Typha latifolia and Typha angustifolia are quite dominant in Hokera wetland (Mir et al., 2009;Bano et al., 2018) and thus of management concern. These species also have been documented noxious wetland weeds elsewhere in Australia (Kay & Hoyle, 2001), North America (Finkelstein, 2003); Great Lakes (Trebitz & Taylor, 2007;Tulbure et al., 2007) and Indian wetlands Khan & Shah, 2010). The huge inflow of wastes and the silt containing nitrate and ammonical nitrogen from the residential areas into the wetlands (Bhat & Pandit, 2014) boosts the excessive growth of macrophytic vegetation Pandit & Kumar, 2006) in Hokera wetland (Dar et al., 2014), especially P. australis, S. ramosum and T. angustifolia, thereby converting marshy areas into rather a terrestrial grassland-type systems. ...
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In view of huge ecological impacts and exorbitantly high economic costs of biological invasions, the risk assessment for timely prediction of potential invaders and their effective management assumes central importance, yet having been little addressed. Hence, we did the risk analysis of 39 plant species, including both alien and fast-spreading native species, in Hokera wetland, an important Ramsar site in Kashmir Himalaya, using the post-border Australian Weed Risk Management (AWRM) framework. Based on the AWRM scores, we listed these species into different categories, such as alert, destroy infestation, contain spread, manage weed, manage sites and monitor, with management implications. Out of the eight decisions created for Hokera wetland, alien Alternanthera philoxeroides was identified as ‘alert species’, while Typha angustifolia, Typha latifolia, Phragmites australis, Sparganium ramosum and Myriophyllum aquaticum were placed under the ‘manage weed’ category of the management priorities. To check the predictability and reliability of the AWRM scheme, we developed the receiver operating characteristic (ROC) curve that yielded a positive diagonal value of above 0.5, with 88.6% and 83.1% area under the curve for comparative weed risk (CWR) score and the feasibility of coordinated control (FOC) score, respectively. The outcomes of the ROC analysis were compared with the results of the WRM evaluation of other regions across the globe. Our results indicate that the risk assessment using the AWRM model is quite efficient at discriminating and flagging the most troublesome plant species and offsetting their impacts on native biodiversity and ecosystem functioning in wetland ecosystems. Given the growing threat of biological invasions in the protected areas, we recommend an integrated and strategic approach, well informed by the data on the species biology and ecology, in the form of the AWRM management system to effectively deal with the alarmingly spreading species.
... Regional experts have ranked invasive species and invasive species-related issues as three of the top five most important stressors for the Laurentian Great Lakes and their associated wetlands (Smith et al., 2015). Invasive species in these Great Lakes have been shown to outcompete or crowd out native species (Janssen and Jude, 2001;Tulbure et al., 2007), create lower habitat quality (Lawrence et al., 2016), and act as a nuisance to area businesses and residents (Pejchar and Mooney, 2009). The management of invasive species in Great Lakes wetlands is complicated by the systems acting as a sink for materials originating from the surrounding landscape (Zedler and Kercher, 2004) and their patchwork of ownership, making them difficult to manage in isolation. ...
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The coordinated use of ecological data is critical to the proper management of invasive species in the coastal wetlands of the Laurentian Great Lakes. Researchers and government programs have been increasingly calling for the use of data in management activities to increase the likelihood of success and add transparency in decision making. Web-enabled databases have the potential to provide managers working in Great Lakes coastal wetlands with relevant data to support management decisions. To assess the potential value of these databases to managers in Laurentian Great Lakes states, we surveyed wetland managers to determine their current data usage as well as their future data interests and catalogued the online databases currently available. Surveys were disseminated via email to managers in 56 different organizations overseeing invasive species management efforts in Great Lakes coastal wetlands; 46 responses were included in this analysis. Of the survey respondents, all reported using raw biotic data for decision making, (i.e. presence of target species) but many indicated that they would prefer to incorporate a greater variety of data, as well as more complex information. Our survey found that managers used web-enabled databases, but most databases that we catalogued only provided presence data for wetland biota. We concluded that databases can provide the types of data sought by invasive species managers but have unmet potential to be integrated into responsive management processes.
... In recent times, as with most other Ramsar wetlands across the world, the HNWs is threatened by invasive species and human activities such as the invasion of Typha australis in the wetland's key areas; Nguru Lake and Marma channel (the designated Ramsar sites), deforestation, and over-collection of fuelwoods (Galushin et al. 2003;Thiollay 2006a, b;Tulbure et al. 2007). It is overgrazing, fishing activities, waterbird poisoning, and trapping that are the culprits in the decline of waterbird populations in the HNWs (Ringim and Harry 2017;pers. ...
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The Hadejia–Nguru Wetlands (HNWs) is among the most important wetlands in sub-Saharan Africa by supporting an important number of waterbird populations and human livelihoods. This paper reports the population of waterbird species counted within a five-year survey; 2015, 2016, 2018, 2019 and 2020. The data were analyzed using the Pivot Table function in Microsoft Excel and R programming language. Results reveal 1,139,666 individual birds of 93 species from 19 families over the survey period. The average waterbird population was 40,330 individuals in 2015 (species richness, S, 64), 33,281 in 2016 (S = 61), 49,950 in 2018 (S = 64), 40,773 in 2019 (S = 72), and 63,598 in 2020 (S = 70). The bird families with the highest bird species were Accipitridae (18 species), followed by Ardeidae (11 species), then Anatidae and Scolopacidae (10 species each). The three waterbird species with the most population were Dendrocygna viduata, 443, 652 (39%) followed by Spatula querquedula 234,074 (21%) and Calidris pugnax 168,142 (15%), accounting for 75% of the total individual birds recorded. Generally, the waterbird population in the HNWs did not show declines over the survey period even though there was evidence of fluctuation. Four species of conservation concern were recorded; Beaudouin’s Snake Eagle Circaetus beaudouini (Vulnerable), Hooded Vulture Necrosyrtes monachus (Critically endangered), Martial Eagle Polemaetus bellicosus (Vulnerable) and Pallid Harrier Circus macrourus (Near Threatened). The majority of the waterbird populations had a global decreasing population trend, indicating the need for urgent conservation intervention locally. More monitoring and census at a different season of the year and increased awareness of conservation in the wetland would certainly help in the long-term conservation of waterbirds and their habitats. This is especially true because of the significance of the HNWs as a wintering ground and stopover site for Afro-Palearctic migratory waterbirds.
... Phragmites establishes dense monocultures and thick litter layers that overcrowd and outcompete native vegetation (Windham and Meyerson 2003;Holdredge and Bertness 2011). Such effects reduce overall plant diversity and structural complexity within the invaded system, which may subsequently limit the habitat available for native wildlife (Ailstock et al. 2001;Tulbure et al. 2007). Despite some reported use of Phragmites by native fauna in North America (Kiviat 2013(Kiviat , 2019, it is typically thought to provide poor wildlife habitat (Meyerson et al. 2000). ...
Article
Wetlands provide essential habitat for shorebirds, songbirds, and waterfowl. Invasive species can disrupt trophic interactions within wetlands by altering the arthropod assemblages on which birds rely. An invasive grass species, Phragmites australis (common reed), has invaded wetlands across North America, including those surrounding the Great Salt Lake, Utah, U.S.A. Phragmites outcompetes native vegetation and alters habitat for resident and migratory birds, yet how Phragmites affects arthropod assemblages is unclear. To address these knowledge gaps, this study investigated how arthropod assemblages differ between native and invasive vegetation in Great Salt Lake wetlands. We examined the arthropod assemblages found within three native habitats as well as in Phragmites-invaded areas. There were few differences in arthropod assemblages between Phragmites and two native habitats (hardstem bulrush, Schoenoplectus acutus and alkali bulrush, Bolboschoenus maritimus). Arthropod assemblages differed between Phragmites and the native Salicornia rubra (pickleweed), which differed markedly from the other plant species in structure, biomass, and related site conditions. Identifying how arthropods interact with Phragmites and native vegetation is critical to recognizing how to effectively manage wetlands for bird habitat. By gaining an understanding of these relationships, arthropod biomass, abundance, diversity, and assemblage composition could serve as assessment metrics for determining wetland management success.
... However, some authors have warned of year effects in certain circumstances: fluctuations in habitat scores across years due to natural disturbance regimes (e.g., intense floods, droughts, wind storms). Natural year effects have only been discerned in a few, relatively unique situations thus far (Tulbure et al. 2007). ...
Article
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Floristic Quality Assessment (FQA) measures have become extraordinarily influential ecological metrics in North America over the past 20 yr. Government agencies, conservation organizations, land managers, and researchers alike utilize this plant‐based measure to evaluate habitat conservation value, ecological integrity, and naturalness. Its relative uniqueness, utility, and ease of use, among vegetation measures, portend the continued popularity of FQA going forward. FQA's use and influence far exceeds its study—where the literature addressing questions and criticisms regarding its methodology and ecological meaning has not kept pace with reliance upon it. Furthermore, the lack of literature review has led to disorder and confusion among its users. This review addresses these issues in three parts. First, it concisely explains the metrics and their methods, and most importantly, it synthesizes the often‐misinterpreted conceptual basis behind FQA. The bulk of the review then tackles common questions from researchers and non‐technical users alike regarding the measures. It does this with two lists. The first list reviews FQA's most common criticisms and summarizes evidence for and against them. The second list confronts the most common mistakes surrounding FQA, regarding both its application and misunderstanding in the literature. In each instance, straightforward guidelines and answers to uncertainties are emphasized.
... Newly created shallow-water areas will offer potential new habitat for establishment of submergent aquatic vegetation and coastal wetland communities. But exposed lakebed areas may be vulnerable to the expansion of invasive species such as Phragmites australis (e.g., Tulbure et al. 2007). ...
... Saltonstall (2002) identified 27 genetically distinct groups (haplotypes) worldwide, of which 11 have been found in North America. Over the past two decades, the European haplotype M began to make rapid incursions into Canada and the U.S., especially into coastal wetlands of the Laurentian Great Lakes (Wilcox et al. 2003;Tulbure et al. 2007;Wilcox 2012;Bourgeau-Chavez et al. 2015), and along highway corridors (Saltonstall 2002;Lelong et al. 2007). This haplotype exhibits invasive characteristics, including its ability to aggressively colonize exposed mud flats sexually (through seeds), and then expand asexually (through rhizomes) to form dense monocultures that inhibit biodiversity of other plants and wildlife (Meyerson et al. 2000;Markle and Chow-Fraser 2018). ...
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Phragmites australis (Cav.) Trin. ex Steudel subspecies australis is one of the worst plant invaders in wetlands of North America. Remote sensing is the most cost-effective method to track its spread given its widespread distribution and rapid colonization rate. We hypothesize that the morphological and/or physiological features associated with different phenological states of Phragmites can influence their reflectance signal and thus affect mapping accuracies. We tested this hypothesis by comparing classification accuracies of cloud-free images acquired by Landsat 7, Landsat 8, and Sentinel 2 at roughly monthly intervals over a calendar year for two wetlands in southern Ontario. We used the Support Vector Machines classification and employed field observations and image acquired from unmanned aerial vehicle (8 cm) to perform accuracy assessments. The highest Phragmites producer’s, user’s, and overall accuracy (96.00, 91.11, and 88.56% respectively) were provided by images acquired in late summer and fall period. During this period, green, Near Infrared, and Short-Wave Infrared bands generated more unique reflectance signals for Phragmites. Both Normalized Difference Vegetation Index and Normalized Difference Water Index showed significant difference between Phragmites and the most confused classes (cattail; Typha latifolia L., and meadow marsh) during the late summer and fall period. Since meadow marsh separated out best from Phragmites and cattail in the February image, we used it to mask the meadow marsh in the July image to reduce confusion. The unique reflectance signal of Phragmites in late summer and fall is likely due to prolonged greenness of Phragmites when compared to other wetland vegetation, large, distinct inflorescence, and the water content of Phragmites during this period.
... During the study period (growing seasons of 2015 and 2016) cattail covered about 41% of the 61 ha that comprises the estuarine wetland ((Rey-Sanchez et al., 2018); Figure 1). Cattail is a cosmopolitan macrophyte present in wetlands throughout the temperate zone, from the Arctic Circle to 30°S (Schulthorpe, 1967) and is usually recognized as an invasive species in Great Lakes coastal wetlands (Tulbure et al., 2007). The cattail patches present in OWC feature high-density monocultures with some associated submerged aquatic vegetation, mostly species from the Potamogeton genera. ...
Article
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Wetlands are the most important natural source of methane (CH4) to the atmosphere, and there is still considerable uncertainty of CH4 flux and net carbon budgets of wetlands. This uncertainty is due in part to the complex role of wetland vegetation in controlling methane production, oxidation and transport, which challenge the modeling and forecast of CH4 fluxes. We combined CH4 and carbon dioxide (CO2) fluxes measured by the eddy covariance technique during two consecutive growing seasons with continuous measurements of water levels and water temperature in a Typha angustifolia L patch of a temperate wetland. We seek to evaluate the role of vegetation in CH4 flux processes. To this end, we determined the relationship between CH4 and CO2 fluxes, directly and indirectly linked to plant activity. Our results indicated significant but opposing relationships between CH4 and CO2 fluxes during the daytime and nighttime. Consequently, when analyzed on a diel timescale, this relationship was not significant. Both CH4 and CO2 fluxes were highly dependent on environmental drivers, and thus, the correlations observed at both the nighttime and daytime were likely the result of a shared response to environmental variables. Focusing on water temperature (the most commonly observed environmental variable in wetlands) and water level (the most commonly controlled one) as operational control variables for wetlands, we identified “hot” condition combinations when CH4 flux and net ecosystem CO2 uptake are maximized at half hourly and diel scales.
... As such, Typha exhibits greater P retention and growth when persistently inundated (Boers and Zedler 2008). Prolonged low-water conditions have also been linked with increased presence and dominance of invasive Typha (Tulbure et al. 2007). These low-water effects have been documented even in otherwise-intact northern LGL coastal wetlands (Lishawa et al. 2010), likely due to increasing propagule pressure in the region. ...
Article
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Typha is an iconic wetland plant found worldwide. Hybridization and anthropogenic disturbances have resulted in large increases in Typha abundance in wetland ecosystems throughout North America at a cost to native floral and faunal biodiversity. As demonstrated by three regional case studies, Typha is capable of rapidly colonizing habitats and forming monodominant vegetation stands due to traits such as robust size, rapid growth rate, and rhizomatic expansion. Increased nutrient inputs into wetlands and altered hydrologic regimes are among the principal anthropogenic drivers of Typha invasion. Typha is associated with a wide range of negative ecological impacts to wetland and agricultural systems, but also is linked with a variety of ecosystem services such as bioremediation and provisioning of biomass, as well as an assortment of traditional cultural uses. Numerous physical, chemical, and hydrologic control methods are used to manage invasive Typha, but results are inconsistent and multiple methods and repeated treatments often are required. While this review focuses on invasive Typha in North America, the literature cited comes from research on Typha and other invasive species from around the world. As such, many of the underlying concepts in this review are relevant to invasive species in other wetland ecosystems worldwide.
... This study suggests that anthropogenic disturbance patterns correspond to microbial community differences in Great Lakes coastal wetlands as is consistent with other taxonomic groups such as plants, birds, fish and invertebrates (Howe et al. 2007;Tulbure, Johnston and Auger 2007;Uzarski et al. 2009;Cooper, Gyekis and Uzarski 2012;Uzarski et al. 2017). Microbial communities appear to respond uniquely to potential anthropogenic influence, as diversity increased with increasing nutrient levels in the coastal wetlands explored in this study. ...
Article
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Microbial communities within the soil of Laurentian Great Lakes coastal wetlands drive biogeochemical cycles and provide several other ecosystem services. However, there exists a lack of understanding of how microbial communities respond to nutrient gradients and human activity in these systems. This research sought to address the lack of understanding through exploration of relationships between nutrient gradients, microbial community diversity, and microbial networks. Significant differences in microbial community structure were found among coastal wetlands within the western basin of Lake Erie and all other wetlands studied (three regions within Saginaw Bay and one region in the Beaver Archipelago). These diversity differences coincided with higher nutrient levels within the Lake Erie region. Site-to-site variability also existed within the majority of the regions studied, suggesting site-scale heterogeneity may impact microbial community structure. Several subnetworks of microbial communities and individual community members were related to chemical gradients among wetland regions, revealing several candidate indicator communities and taxa that may be useful for Great Lakes coastal wetland management. This research provides an initial characterization of microbial communities among Great Lakes coastal wetlands and demonstrates that microbial communities could be negatively impacted by anthropogenic activities.
... By contrast, P. australis showed a maximum 20% biomass increase at a depth of 10 cm, no increase at 40 cm, and 100% mortality at 70 cm, indicating that the plant did not grow well in deep water. Previous studies have found that water depth does not suppress growth of Typha species (Tulbure et al. 2007) while water depth is the major factor that affects growth of P. australis (Engloner 2009). Plant nitrogen content decreased significantly with the water depth in both species (Fig. 2A). ...
Article
Two major emergent macrophytes, Phragmites australis and Typha angustifolia, show a clear zonation with respect to water depth, i.e., P. australis occupies shallower water than T. angustifolia. However, the reasons for this interspecific difference is unclear. Therefore, this study focused on the features that enable T. angustifolia to survive at greater water depths than P. australis. In both outdoor and greenhouse experiments, P. australis did not survive at the deepest water depth and showed significantly lower biomass, nitrogen content, and photosynthesis in most deep and/or aerated water than T. angustifolia. Differences in tolerances to changes in the water depth and responses to root aeration may underlie the clear zonation of the two species. As T. angustifolia and P. australis are both very common in wetlands around the world, understanding the causal factors determining their depth distributions, such as differences in photosynthetic rate at different depths, will be of great importance for managing or controlling these species.
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Invasive plant management is a key focus of wetland managers, and considerable resources have been devoted to control of non-native Phragmites australis in many Great Lakes coastal wetlands. This study examined short-term (1-year) impacts of herbicide management by comparing wetland plant productivity, nutrient availability, and plant communities before and after herbicide treatment in two coastal wetlands. We also monitored a third wetland in years 3–5 following herbicide treatment. After herbicide treatment, annual aboveground net primary production and plant nitrogen and phosphorus uptake decreased dramatically (by an average of 88%, 80% and 89% respectively; p < 0.05); porewater soluble reactive phosphorus (SRP) and surface water ammonium increased at one site (p < 0.05), while porewater ammonium increased at the other site (p < 0.05); porewater dissolved organic carbon concentrations increased at both sites (p < 0.05); and porewater nitrate did not change at either site. Despite large reductions in Phragmites biomass following herbicide treatment, floristic quality did not improve. When scaled to the area surrounding Lake Erie’s Western Basin treated with herbicide in 2012, the reduction in plant nutrient uptake accounted for 24 × 10³ kg of phosphorus and 159 × 10³ kg of nitrogen, nutrients potentially available for export to coastal waters. This amount was small relative to average annual (2009–2014) loading from the Maumee River, but similar in magnitude to summer loading in 2012 (57% of total nitrogen and 478% of SRP riverine loading), a year of low discharge and loading. Our results highlight the trade-offs inherent in managing invasive plants.
Article
Remotely sensed land cover data enable characterization of avian habitat over large spatial scales, which can be applied to regional conservation planning. Black Terns (Chlidonias Niger) have been declining in the U.S. Great Lakes region for decades. Although causes of the decline are not well understood, habitat loss and degradation are viewed as major barriers to recovery. The Upper Mississippi River and Great Lakes Region Joint Venture, a partnership for bird conservation in the Upper Midwest, developed a landscape suitability index for the wetland-breeding Black Tern based on remotely sensed land cover to choose habitat to enhance or restore. We tested the validity of this index and compared it to an alternative index we constructed from results of field surveys. Over 2 breeding seasons, we surveyed for presence of Black Tern breeding colonies in 158 wetlands across the Great Lakes region and compared our findings with predictions of the existing index. We used our first season of surveys, numerous remotely sensed landscape variables, and random forest classification to build our alternative index. Key predictors of Black Tern colony presence in the alternative index were wetland area, wetland type (emergent vegetation, open water, or combination), and area of wetlands available for foraging within 2 km. The 2 indices performed similarly well, correctly identifying categories of sites most likely to host Black Terns, but even high-suitability sites had <20% predicted occupancy probability. The best use of these and similar indices is in prioritizing restoration projects at a regional scale by identifying sites with potential for use.
Article
Tidal marsh wetlands in the Yellow River Delta provide valuable eco‐services to the local population and global ecology. However, this area is suffering from serious degradation under the stresses of social development and climate change. Hydrological connectivity, a new framework in hydrology and ecology, has been proposed as the main factor affecting the ecological processes in coastal wetlands; however, its role in hydrology–soil–vegetation interactions remains unclear. In this study, we parametrically quantified the hydrological connectivity in the tidal marsh wetlands and analyzed its relationship with Phragmites australis, one of the dominant species in this area. Our results showed threshold‐like effects on the interaction between hydrological connectivity and P. australis on the plot scale. When biomass is lower than 2.2 kg/m², the population density and structure size were found to increase with hydrological connectivity. When the biomass is higher than the threshold, the plots disconnected hydrologically because of high water consumption. Compared with soil chemistry, salinity, and water soil content, hydrological connectivity in the surface soil layer is more strongly linked to the plant traits and spatial structure in the tidal marsh wetlands due to the narrow ranges of other variables. Based on the authors’ analysis, the researchers do not recommend dense plantation of P. australis, especially near the freshwater sources in the tidal marsh, because of its high reproduction ability and competitive nature, which may cut the freshwater connectivity off, lowering the richness of plant species and habitat diversity. This article is protected by copyright. All rights reserved.
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Phragmites australis is a cosmopolitan plant species with high intraspecific diversity and phenotypic plasticity. Due to its variability and large ecological niche breadth, subgroups of P. australis have become invasive in North America, and this invasion has been recognized late. While this cryptic invasion on the American continent has received much attention, little is known about the potential invasiveness of other subgroups, especially within Asian/Australian P. australis. We therefore compared the performance of three subgroups within the Asian/Australian group: a freshwater (CN) and an estuarine (YRD) subgroup collected in China and a genetically closely related subgroup collected from Australia (FEAU), grown in two common gardens in China. Our results showed that the FEAU subgroup had no strong invasive potential, as its total biomass, height, shoot number, specific leaf area, and stomatal conductance were lower than that of the two native subgroups. All three subgroups responded similarly with most traits to the different climates of the gardens, albeit with different response strength, expressed as phenotypic plasticity indices. The potential cryptic invasion risk of the FEAU subgroup in China seems to be low, since its functional traits showed low competitiveness and most traits with the lowest plasticity occurred in FEAU. However, caution is still advised, because other invasive mechanisms, such as enemy release or the performance under extreme environmental conditions were not tested in our study.
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Plant invasions often lead to homogenization of plant communities, but the potential for homogenization of other trophic levels is understudied in many systems. Biotic communities in coastal wetlands are closely tied to daily and yearly water-level fluctuations. We compared the bird community in invasive Phragmites australis (European common reed) habitat and remnant, uninvaded marsh in a year with average water depths and a year with above-average water depths in Long Point (Ontario, Canada), a World Biosphere Reserve. Our results demonstrate the spatial and temporal homogenization of the wetland bird community following P. australis invasion. The bird community present in P. australis was a nested subset of the species present in remnant marsh, and total beta diversity in P. australis habitat decreased when water depths were above average. In contrast, total beta diversity was high in remnant marsh vegetation. The distinctively structured vegetation zones in remnant marsh yield structural complexity and habitat heterogeneity that support greater taxonomic turnover in the bird community. These results provide evidence that invasion by a plant has resulted in the biological homogenization of the wetland bird community and illustrate that habitat use will change with prevailing environmental conditions, such as high- and low-water levels.
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In recent decades the grass Phragmites australis has been aggressively invading coastal, tidal marshes of North America, and in many areas it is now considered a nuisance species. While P. australis has historically been restricted to the relatively benign upper border of brackish and salt marshes, it has been expanding seaward into more physiologically stressful regions. Here we test a leading hypothesis that the spread of P. australis is due to anthropogenic modification of coastal marshes. We did a field experiment along natural borders between stands of P. australis and the other dominant grasses and rushes (i.e., matrix vegetation) in a brackish marsh in Rhode Island, USA. We applied a pulse disturbance in one year by removing or not removing neighboring matrix vegetation and adding three levels of nutrients (specifically nitrogen) in a factorial design, and then we monitored the aboveground performance of P. australis and the matrix vegetation. Both disturbances increased the density, height, and biomass of shoots of P. australis, and the effects of fertilization were more pronounced where matrix vegetation was removed. Clearing competing matrix vegetation also increased the distance that shoots expanded and their reproductive output, both indicators of the potential for P. australis to spread within and among local marshes. In contrast, the biomass of the. matrix vegetation decreased with increasing severity of disturbance. Disturbance increased the total aboveground production of plants in the marsh as matrix vegetation was displaced by P. australis. A greenhouse experiment showed that, with increasing nutrient levels, P. australis allocates proportionally more of its biomass to aboveground structures used for spread than to belowground structures used for nutrient acquisition. Therefore, disturbances that enrich nutrients or remove competitors promote the spread of P. australis by reducing belowground competition for nutrients between P. australis and the matrix vegetation, thus allowing P. australis, the largest plant in the marsh, to expand and displace the matrix vegetation. Reducing nutrient load and maintaining buffers of matrix vegetation along the terrestrial-marsh ecotone will, therefore, be important methods of control for this nuisance species.
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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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Primary succession of plant communities directed toward a climax is not a typical occurrence in wetlands because these ecological systems are inherently dependent on hydrology, and temporal hydrologic variability often causes reversals or setbacks in succession. Wetlands of the Great Lakes provide good examples for demonstrating the implications of hydrology in driving successional processes and for illustrating potential misinterpretations of apparent successional sequences. Most Great Lakes coastal wetlands follow cyclic patterns in which emergent communities are reduced in area or eliminated by high lake levels and then regenerated from the seed bank during low lake levels. Thus, succession never proceeds for long. Wetlands also develop in ridge and swale terrains in many large embayments of the Great Lakes. These formations contain sequences of wetlands of similar origin but different age that can be several thousand years old, with older wetlands always further from the lake. Analyses of plant communities across a sequence of wetlands at the south end of Lake Michigan showed an apparent successional pattern from submersed to floating to emergent plants as water depth decreased with wetland age. However, paleoecological analyses showed that the observed vegetation changes were driven largely by disturbances associated with increased human settlement in the area. Climate-induced hydrologic changes were also shown to have greater effects on plant-community change than autogenic processes. Other terms, such as zonation, maturation, fluctuations, continuum concept, functional guilds, centrifugal organization, pulse stability, and hump-back models provide additional means of describing organization and changes in vegetation; some of them overlap with succession in describing vegetation processes in Great Lakes wetlands, but each must be used in the proper context with regard to short- and long-term hydrologic variability.
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Phragmites australis (common reed) has expanded in many wetland habitats. Its ability to exclude other plant species has led to both control and eradication programs. This study examined two control methods—herbicide application or a herbicide-burning combination—for their efficacy and ability to restore plant biodiversity in non-tidal wetlands. Two Phragmites-dominated sites received the herbicide glyphosate. One of these sites was burned following herbicide application. Plant and soil macroinvertebrate abundance and diversity were evaluated pre-treatment and every year for four years post-treatment using belt transects. The growth of Phragmites propagules—seeds, rhizomes, and rooted shoots—was examined in the greenhouse and under bare, burned, or vegetated soil conditions. Both control programs greatly reduced Phragmites abundance and increased plant biodiversity. Plant re-growth was quicker on the herbicide-burn site, with presumably a more rapid return to wetland function. Re-growth at both sites depended upon a pre-existing, diverse soil seed bank. There were no directed changes in soil macroinvertebrate abundance or diversity and they appeared unaffected by changes in the plant community. Phragmites seeds survived only on bare soils, while buried rhizomes survived under all soil conditions. This suggests natural seeding of disturbed soils and inadvertent human planting of rhizomes as likely avenues for Phragmites colonization. Herbicide control, with or without burning, can reduce Phragmites abundance and increase plant biodiversity temporarily. These changes do not necessarily lead to a more diverse animal community. Moreover, unless Phragmites is eradicated and further human disturbance is prohibited, it will likely eventually re-establish dominance.
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Wetlands seem to be especially vulnerable to invasions. Even though ≤6% of the earth's land mass is wetland, 24% (8 of 33) of the world's most invasive plants are wetland species. Furthermore, many wetland invaders form monotypes, which alter habitat struc-ture, lower biodiversity (both number and "quality" of species), change nutrient cycling and productivity (often increasing it), and modify food webs. Wetlands are landscape sinks, which accumu-late debris, sediments, water, and nutrients, all of which facilitate invasions by creating canopy gaps or accelerating the growth of op-portunistic plant species. These and other disturbances to wetlands, such as propagule influx, salt influx, and hydroperiod alteration, create opportunities that are well matched by wetland opportunists. No single hypothesis or plant attribute explains all wetland inva-sions, but the propensity for wetlands to become dominated by invasive monotypes is arguably an effect of the cumulative impacts associated with landscape sinks, including import of hydrophytes that exhibit efficient growth (high plant volume per unit biomass).
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Interdependence among disturbance events, ecosystem properties, and biological invasions often make causal relationships difficult to discern. For example, Phragmites australis invasion in mid-Atlantic salt marshes is often associated with disturbances that create well-drained features as well as with low sulfide concentrations, but explanations of these associations have been elusive. We tested experimentally: 1) that disturbances increasing wetland drainage facilitate Phragmites invasion by altering sulfide concentrations and salinity; 2) that translocation allows plants to spread beyond drainage areas; and 3) that plants can then lower edaphic stress through pressure ventilation of the rhizosphere and promote further expansion. At the invasion front, treatments of 1) severing rhizomes to halt translocation and 2) combined severing with clipping dead culms to limit ventilation of the rhizosphere killed most culms, but did not affect pore water chemistry. In already invaded areas, severing and clipping reduced culm height and panicle production, severing alone and in combination with clipping also raised sulfide and ammonium concentrations in the root zone. There were no treatment effects on plant performance or pore water chemistry along mosquito ditches, where sulfide concentrations were negligible. Small-scale hydrological alterations such as ditches appear to provide suitable sites for the establishment of Phragmites because soils are well-drained and are low in free sulfides. Subsequent expansion into more hostile areas occurs through translocation, with well-drained areas acting as sources for essential substances. Once established, the plant increases rhizosphere oxygenation and lowers sulfide concentrations.
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In spite of its long history,Phragmites australis’ (Cav.) Trin ex Stuedel invasion in tidal marshes defies explanation. Initial establishment in these systems is particularly perplexing, because seedlings and rhizome fragments do not perform well in poorly drained saline environments. We tested the possibility that dispersal and burial of large rhizomes, periods of low salinity, and localized, well-drained areas facilitate initial establishment in brackish marshes. In a greenhouse we exposed large and small rhizomes to two drainage treatments: mimics of poorly-drained, high marsh interiors and mimics of well-drained, mosquito ditch banks. In well-drained treatments we exposed rhizomes to one of three salinity treatments: fresh, natural salinity regime of an invaded brackish water marsh, and a 2-wk freshwater window followed by a natural salinity regime. Small rhizone fragments did not emerge in saline treatments or treatments with high water tables, while emergence was spotty in well-drained freshwater treatments. Large rhizomes emerged only in well-drained, treatments. For large rhizomes, growth, survival, and clonal spread decreased when exposed to the natural salinity regime, but improved with exposure to the 2-wk freshwater window. These results suggest that dispersal and burial of larger rhizomes, well-drained features, and low salinity windows following dispersal improve the chances of successful establishment. These results help explain case-specific historical links between establishment and such human activities as hydrological alterations, construction activities, and lowered salinity.
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This paper compares the available North Americanliterature and data concerning several ecologicalfactors affecting Phragmites australisin inlandfreshwater, tidal fresh, and tidal brackish marshsystems. We compare aboveground productivity, plantspecies diversity, and sediment biogeochemistry; andwe summarize Phragmiteseffects on faunalpopulations in these habitats. These data suggest thatPhragmitesaboveground biomass is higher thanthat of other plant species occurring in the samemarsh system. Available data do not indicate anysignificant difference in the aboveground Phragmitesbiomass between marsh types, nor doesthere appear to be an effect of salinity on height.However, Phragmitesstem density wassignificantly lower in inland non-tidal freshwatermarshes than in tidal marshes, whether fresh orbrackish. Studies of the effects of Phragmiteson plant species richness suggest that Phragmitesdominated sites have lower diversity.Furthermore, Phragmiteseradication infreshwater sites increased plant diversity in allcases. Phragmitesdominated communities appearto have different patterns of nitrogen cyclingcompared to adjacent plant communities. Abovegroundstanding stocks of nitrogen (N) were found to behigher in Phragmitessites compared to thosewithout Phragmites. Porewater ammonium(NH4 +) did not differ among plant covertypes in the freshwater tidal wetlands, but inbrackish marshes NH4 +was much higher inSpartinaspp. than in neighboring Phragmitesstands. Faunal uses of Phragmitesdominated sites in North America were found to vary bytaxa and in some cases equaled or exceeded use ofother robust emergent plant communities. In light ofthese findings, we make recommendations for futureresearch.
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The spread of invasive taxa, includingLythrum salicaria, Typha × glauca, Myriophyllum spicatum, Phalaris arundinacea, andPhragmites australis, has dramatically changed the vegetation of many wetlands of North America. Three theories have been advanced to explain the nature of plant invasiveness. Aggressive growth during geographic expansion could result because 1) growth is more favorable under new environmental conditions than those of resident locales (environmental constraints hypothesis); 2) herbivores may be absent in the new locale, resulting in selection of genotypes with improved competitive ability and reduced allocation to herbivore defenses (evolution of increased competitive ability hypothesis); and 3) interspecific hybridization occurred between a new taxon and one existing in an area, resulting in novel phenotypes with selective advantages in disturbed sites or phenotypes that can grow under conditions not favorable for either parent (introgression/hybrid speciation hypothesis). A review of published literature found few studies that compare the growth and dynamics of invasive populations in their new range versus those in historic ranges. However, there is evidence that hydrologic alterations could facilitate invasions byTypha × glauca andPhalaris arundinacea and that increased salinity promoted spread ofTypha angustifolia (parental taxon) andPhlaris arundinacea and that increased salinity promoted spread ofTypha angustifolia (parental taxon) andPhragmites australis. The potential for reduced herbivory causing aggressive growth is greatest forLythrum salicaria. Introgressive hybridization is potentially a cause of invasiveness for all five species but has been established only forTypha × glauca andLythrum salicaria.
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Over the past several decades, populations of the common reed, Phragmites australis, have expanded rapidly in salt marshes of coastal North America, creating dramatic changes in community composition. Populations of Phragmites in coastal wetlands of the Great Lakes may similarly threaten the ecological integrity of these inland wetland communities. Strategies for the conservation of biodiversity in these wetlands should be informed by an understanding of both the recent trends and the historic role of Phragmites in these wetlands. A combination of paleoecological and genetic analyses was used to determine when Phragimites became established in a Lake Superior coastal wetland and whether the source of Phragmites was native or non-native populations. Radiocarbon-dated stratigraphic changes in the abundance of pollen and macroscopic plant remains were used to infer the timing of vegetation changes in the wetland. From about 1100–490 14C yr ago, low water levels were associated with a lowland conifer forest with wetland swales at this site. At about 490 BP, conifers became less common, and peatlands became established at the site, perhaps in response to higher water levels in the wetland. There is no evidence that Phragmites grew at the site until the last several decades, suggesting that it is not native to this wetland and that its recent expansion may create significant changes in the wetland community. However, genetic data from chloroplast DNA sequences and microsatellite markers indicate that it is a variety that is native to North America and common throughout the Midwest. Our results suggest that human-induced changes in the landscape in combination with long-term environmental changes may play an important role in the expansion of native Phragmites populations.
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Over the past century, the distribution and abundance ofPhragmites australis (common reed) has dramatically increased in both freshwater and brackish wetlands throughout North America. It has been hypothesized that the increased competitive ability ofPhragmites could be the result of an introduction of a more aggressive genotype. Sequence data from 2 noncoding regions of the chloroplast genome show that, historically, 11 native haplotypes were found across North America and population-structuring distinguishing samples from the Atlantic Coast, Midwest, West, and Gulf Coast regions of the continent was evident. Today a single genetically-distinct haplotype dominates the Atlantic Coast and is also found across the continent in lower frequencies; this type is common in Europe and Asia and has most likely been introduced to North America. Comparisons of modern populations with historic samples show that along the Atlantic Coast, this cosmopolitan type has replaced native haplotypes and it is invading new sites throughout the rest of the country. In the Midwest and West, native populations are still common but introduced populations are found along roadsides throughout the area. Gulf Coast populations are dominated by another population type that is genetically distinct from all other North American population types.
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The objective of this study was to review the relationship between fluctuating water levels and shoreline vegetation dynamics in the Great Lakes. Low water periods allow many plant species and vegetation types to regenerate from buried seeds. A review of published seed bank densities shows that some lakeshores have densities of buried seeds greater than l04 seeds m−2, an order of magnitude greater than densities reported from prairie marshes. High water periods kill dominant species (e.g., Typha sp.), thereby creating gaps which other species can colonize during low water periods. High water also kills woody plants, thereby extending marshes landward. Fluctuating water levels therefore increase the area of shoreline vegetation, and the diversity of vegetation types and plant species. Any stabilization of water levels would likely reduce marsh area, vegetation diversity, and plant species diversity. Four basic shoreline vegetation types (forest and shrub thickets, wet meadow, marsh, and aquatic) can be recognized; both wet meadow and marsh largely result from fluctuating water levels.
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Phragmites expansion into tidal wetlands of North America is most extensive along the northern and middle Atlantic coasts, but over 80% of the US coastal wetland area occurs along the Gulf of Mexico and southern Atlantic coasts and may be susceptible to ongoing expansion. Rapid spread of Phragmites has been documented in freshwater (<0.5 ppt), oligohaline (0.5–5 ppt) and mesohaline (5–18 ppt) tidal wetlands. The advance of Phragmites into tidal wetlands of North America may have been facilitated by widespread coastal changes since European settlement, including disturbance of hydrologic cycles and nutrient regimes; the presence of Phragmites has become a signature of tidal wetland alteration. Although ploidy levels from 2n = 36 to 72 have been documented for Phragmites throughout the continent, no genetics research to date has tested whether recent introduction of aggressive clones could account for Phragmites expansion. A fundamental concern regarding Phragmites expansion, particularly into tidal freshwater wetlands, is the observed reduction in biodiversity as many native species of plants are replaced by a more cosmopolitan species. Commensurate with a shift in habitat type is a reduction in insect, avian and other animal assemblages. Ecosystem services, including support of higher trophic levels, enhancement of water quality and sediment stabilization, however, are not diminished when a tidal wetland becomes dominated by Phragmites, provided that tidal flooding is retained.
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1 The invasion of habitats by non-native plant and animal species is a global phenomenon with potentially grave consequences for ecological, economic, and social systems. Unfortunately, to date, the study of invasions has been primarily anecdotal and resistant to generalization. 2 Here, we use insights from experiments and from long-term monitoring studies of vegetation to propose a new theory in which fluctuation in resource availability is identified as the key factor controlling invasibility, the susceptibility of an environment to invasion by non-resident species. The theory is mechanistic and quantitative in nature leading to a variety of testable predictions. 3 We conclude that the elusive nature of the invasion process arises from the fact that it depends upon conditions of resource enrichment or release that have a variety of causes but which occur only intermittently and, to result in invasion, must coincide with availability of invading propagules.
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Salt marshes play a critical role in the ecology and geology of wave-protected shorelines in the Western Atlantic, but as many as 80% of the marshes that once occurred in New England have already been lost to human development. Here we present data that suggest that the remaining salt marshes in southern New England are being rapidly degraded by shoreline development and eutrophication. On the seaward border of these marshes, nitrogen eutrophication stimulated by local shoreline development is shifting the competitive balance among marsh plants by releasing plants from nutrient competition. This shift is leading to the displacement of natural high marsh plants by low marsh cordgrass. On the terrestrial border of these same marshes, shoreline development is also precipitating the invasion of the common reed, Phragmites, by means of nitrogen eutrophication caused by the removal of the woody vegetation buffer between terrestrial and salt marsh communities. As a consequence of these human impacts, traditional salt marsh plant communities and the plants and animals that are dependent on these habitats are being displaced by monocultures of weedy species.
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Cryptic invasions are a largely unrecognized type of biological invasion that lead to underestimation of the total numbers and impacts of invaders because of the difficulty in detecting them. The distribution and abundance of Phragmites australis in North America has increased dramatically over the past 150 years. This research tests the hypothesis that a non-native strain of Phragmites is responsible for the observed spread. Two noncoding chloroplast DNA regions were sequenced for samples collected worldwide, throughout the range of Phragmites. Modern North American populations were compared with historical ones from herbarium collections. Results indicate that an introduction has occurred, and the introduced type has displaced native types as well as expanded to regions previously not known to have Phragmites. Native types apparently have disappeared from New England and, while still present, may be threatened in other parts of North America.
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Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for apopulation of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.
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Water table is one of the factors controlling the distribution and performance of Phragmites communis Trin. Dense stands normally lose more water through evapotranspiration than is supplied by rain. However, Phragmites grows in a wide range of regimes, and is limited, in Britain, more by nutrient status than by water depth at its wetter limit, and more by competition than by water shortage at its drier limit. Rhizome level and the level of bud initiation are affected by water table, but performance of aerial shoots need not be affected by this, in the ordinary water regimes. Soil aeration, in the range found in East Anglia, does not affect performance, but if cut (or broken) reed is flooded, thus impeding aeration, performance decreases. Once a seasonal pattern of water-level fluctuations is established, departure from this (causing drying in a season the stand is normally flooded) disturbs the growth cycle and lowers the yield.
Article
Water table is one of the factors controlling the distribution and performance of Phragmites communis Trin. Dense stands normally lose more water through evapotranspiration than is supplied by rain. However, Phragmites grows in a wide range of regimes, and is limited, in Britain, more by nutrient status than by water depth at its wetter limit, and more by competition than by water shortage at its drier limit.Rhizome level and the level of bud initiation are affected by water table, but performance of aerial shoots need not be affected by this, in the ordinary water regimes. Soil aeration, in the range found in East Anglia, does not affect performance, but if cut (or broken) reed is flooded, thus impeding aeration, performance decreases. Once a seasonal pattern of water-level fluctuations is established, departure from this (causing drying in a season the stand is normally flooded) disturbs the growth cycle and lowers the yield.
Chapter
A quick dip into the literature on diversity reveals a bewildering range of indices. Each of these indices seeks to characterize the diversity of a sample or community by a single number. To add yet more confusion an index may be known by more than one name and written in a variety of notations using a range of log bases. This diversity of diversity indices has arisen because, for a number of years, it was standard practice for an author to review existing indices, denounce them as useless, and promptly invent a new index. Southwood (1978) notes an interesting parallel in the proliferation of new designs of light traps and new permutations of diversity measures.
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Biological invasions are a threat to ecosystems across all biogeographical realms. Riparian habitats are considered to be particularly prone to invasion by alien plant species and, because riparian vegetation plays a key role in both aquatic and terrestrial ecosystems, research in this field has increased. Most studies have focused on the biology and autecology of invasive species and biogeographical aspects of their spread. However, given that hydrogeomorphological processes greatly influence the structure of riparian plant communities, and that these communities in turn affect hydrology and fluvial geomorphology, scant attention has been paid to the interactions between invasions and these physical processes. Similarly, relatively little research has been undertaken on competitive interactions between alien and native riparian plant species. Further research in these fields is necessary at a variety of spatial and temporal scales before the dynamics of riparian invasions, and their impacts, can be properly understood.
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Because of the damage some do, including threatening biodiversity, invasive species are a current focus of interest, particularly outside Europe. Yet invasion biology is still struggling to become analytic. Progress has been made in quantifying the proportion of invaders that succeed in various ways, and in measuring the degree of that success. Several examples, where the course of invasion has been explained, show the variation in biological processes involved. A detailed analysis, often with experiments and modelling, is necessary for a satisfactory explanation. Prediction is harder than explanation. Attempts at predicting invasions have generally been unsatisfactory. Ten reasons that may contribute to this are discussed. Progress will require defining more precisely what is to be predicted and measuring more quantitatively the ecological properties of species. Even so, predicting the ecological behaviour of a species in a new environment may be effectively impossible.
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Genetic diversity among reed (Phragmites australis) populations from 70 sites in Europe and from 12 sites in other continents was determined using the random amplified polymorphic DNA (RAPD) technique. Based on results from about 1000 reed samples screened with different primers, both polyclonal reed stands, where different clones co-exist either next to each other or intermingle, and monoclonal reed stands were found. Generally a higher diversity of clones was detected from sites on or near shore than in the water. Cluster analysis of genetic similarity coefficients from 30 to 80% demonstrated a high degree of genetic diversity among reed stands world-wide. Lower genetic diversity was detected among samples from any location, with coefficients ranging from 70 to 100%. In general, the genetic distances of investigated reed samples within Europe increase with increasing geographic distances. The reed samples from the other continents formed a separate major cluster in the phenogram.
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The grass Phragmites australis has historically been restricted to the relatively benign upper border of coastal marshes, but over the past century, and particularly in recent decades, it has been spreading aggressively in New England throughout brackish and salt marshes with high soil salinities that are physiologically stressful to the plant. Here I tested the hypothesis that variations in climatic conditions, particularly increased precipitation during the 1997-98 El Niño event, buffer harsh abiotic conditions and enhance the performance of this nuisance species. I monitored the growth and reproductive output of P. australis in the year before, during, and after the 1997-98 El Niño in coastal brackish marshes of southern New England, USA. During the El Niño year, P. australis produced on average 30% more shoots, which were 25% taller, and yielded an order of magnitude more inflorescences than in the other 2 years. Soil porewater salinities were negatively related to precipitation during the 3 years of the study, and the growing season during the El Niño year was one of the wettest of the past century. Consequently, increased precipitation during El Niño may facilitate the spread of less salt-tolerant nuisance and invasive species throughout brackish and salt marshes.
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Prairie marshes in western Canada occur in the Manitoba, Saskatchėwan, and Alberta plains, from 49 to between 50 and 53° N. They are dynamic habitats characterized by fluctuations in water levels and water chemistry. Marsh habitats form an east–west gradient that involves a decrease in precipitation (525 – 350 mm year−1) and an increase in its variability. Within the region, water salinity ranges from fresh to hypersaline. Water levels and chemistry coupled with life history features influence the distribution and successional role of emergent macrophytes. Five dominant emergents have aboveground standing crops of between 425 (Scirpus lacustris ssp. glaucus) and 1750 g m−2 (Typha latifolia). They vary in reproductive strategy and tolerance to water levels and salinity. Scirpus lacustris ssp. glaucus grows in deep water with conductivities < 15 mS cm−1, and spreads vegetatively. Typha latifolia, tolerant of water fluctuations and salinity < 10 mS cm−1, spreads both vegetatively and by seed, particularly under drawdown. Phragmites australis tolerates a wide range of moisture conditions and salinities (< 20 mS cm−1). It propagates primarily by rhizomes and runners. Scirpus lacustris ssp. validus thrives under unstable water regimes but is saline intolerant (< 2 mS cm−1). It is short lived (±3 years) and reproduces primarily by seed. Scirpus maritimus var. paludosus, which dominates western wetlands, tolerates hypersaline conditions (±45 mS cm−1), prefers changing water levels, and spreads both vegetatively and by seed. These environmental and life history features help elucidate wetland dynamics.
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IN maintaining or reconstructing types of herbaceous vegetation in which the density of flowering plants exceeds 20 species/m2-the so-called ``species-rich'' communities, success is often frustrated by competitive exclusion. Here I describe an attempt to identify criteria with which to assess or anticipate the effect of competitive exclusion both at individual sites and in different types of vegetation.