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Results of the repeated measures ANOVA analysis for the Nanticoke and Patuxent River plant species richness data. Means comparisons between the Nanticoke and Patuxent Rivers were not made, so the differences between means are meant to be interpreted within each river separately.
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It is widely accepted that in coastal wetlands a negative relationship exists between plant species richness (number of species)
and salinity. However, the distribution of species richness across estuarine salinity gradients has not been closely examined.
We hypothesized that plant species richness in coastal marshes (i.e., wetlands dominated by he...
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... The findings unambiguously indicate that plant community metrics are associated with longitudinal zonation of the river and not with the history of stressors on the floodplain or the distance from the mainstem river (Table 2). Consistent with this, the importance of longitudinal zonation to the tidal wetland plant community in this and other systems has been shown elsewhere (Sharpe and Baldwin, 2009;Borde et al., 2020). Interestingly, despite the clear univariate and discriminant analysis findings of no significant effects of hydrogeomorphic-regime stressors on wetland plant communities, the discriminant model for physical characteristics by stressor category was improved by adding plants (Section 5.2). ...
... La vegetación riparia viene condicionada, además de por el importante factor hídrico, por el pH de las aguas y de los sustratos de los lechos, orillas y vegas, y por las texturas o granulometrías de los suelos. La naturaleza química del terreno y el agua -en muchos casos determinada por la litología y suelos aguas arriba-y los sólidos transportados, ejercen una influencia permanente en la composición florística de las comunidades vegetales instaladas en los sistemas fluviales (Salinas et al. 2000;Sharpe & Baldwin 2009;Garilleti et al. 2012). Cierto es que su efecto disminuye a lo largo del eje virtual perpendicular al curso fluvial, de manera que el distanciamiento respecto del cauce conlleva un mayor efecto químico de la roca madre. ...
Principales amenazadas y modelos de distribución potencial de bosques de ribera de España ante dos escenarios de cambio climático. Se modela la distribución de especies leñosas formadoras de bosques de ribera -no se modelan comunidades-
... Salinity changes related to climate change (precipitation/evaporation changes) during the lateglacial and Holocene may partly explain the observed changes in wetland floristic composition and richness on truwana/CBI. Precipitation to evaporation ratio was low during the lateglacial and mid-late Holocene (Wilkins et al. 2013;Mackenzie and Moss 2017), and the abundance of Myriophyllum in BRL, tECL and GL suggests the prevalence of moderately saline-brackish (oligohaline) conditions during periods of reduced effective precipitation may have contributed to high floristic richness in wetlands between~14,000 and 12,000 cal yr BP and between~6000 and 2000 cal yr BP (Harris and Kitchener, 2005;Kirkpatrick and Harwood 1983;Sharpe and Baldwin 2009;Engels and Jensen 2009). In contrast, declining wetland floristic richness in the last~2000 years may be associated with extreme levels of salinity in response to drier conditions associated with major declines in effective precipitation during the late Holocene (Herbert et al. 2015;McGlone et al. 1992), as presently seen in southeast Australian wetlands (Goodman 2012;Hart et al. 1990). ...
Understanding long-term ecological development of wetlands is critical to effective management. The islands of Bass Strait, southeast Australia, have several biologically diverse natural wetlands, including Ramsar sites, yet little is known about their ecology. Here, through a multi-proxy palaeoecological approach, we seek to understand how wetland floristic composition and hydrology has changed on truwana/Cape Barren Island (CBI), and how changes in fire regimes have affected wetland integrity and ecological dynamics. We use wetland fossil pollen, non-pollen palynomorphs and sediment geochemistry to reconstruct wetland development and compare it to existing records of terrestrial vegetation and fire regimes from the island. Our results suggest periods of moderately saline–brackish conditions and moderate fire activity supported high floristic richness in wetlands, while floristic richness reduced during periods of extremely high or low salinity or high fire activity. Past changes in precipitation regimes primarily drove water-level changes in wetlands; however, changes in wetland and surrounding terrestrial vegetation cover also contributed to wetland water level dynamics. We recommend long-term monitoring of wetland salinity and water-level changes to track potential changes in wetland floristic richness on truwana/CBI. Controlled fires could also be used to manage wetland biodiversity after careful consideration and experimentation to determine appropriate fire levels that maximize wetland floristic richness and biocultural values.
... Wetlands have been diked, drained, and otherwise hydrologically manipulated for centuries across the globe Kercher 2005, Gedan et al. 2009). Investigating the response of wetland diversity to hydrologic modification is tractable partially because wetland plants have strong responses to hydrologic stress (Mitsch and Gosselink 2007), and wetlands typically have a limited pool of foundational species, especially in estuaries (Sharpe and Baldwin 2009). Wetlands also often occur as discrete patches across landscapes, allowing comparison among distinct sites that have similar environmental drivers (Grewell et al. 2007). ...
... With scarce tidal freshwater wetland data available, a broader effort is needed to clarify overall patterns of tidal estuarine plant diversity, perhaps by combining several large datasets (e.g., Vasey et al. 2012, the current study). We hypothesize that diversity when emphasizing rare species is maximized in tidal fresh wetlands, or is at least equivalent between tidal fresh and brackish wetlands (Sharpe and Baldwin 2009). ...
... Comparing diversity between tidal wetland types requires an approach that incorporates several diversity metrics, which can differentiate rare and dominant species patterns. Other studies have shown oligohaline and brackish tidal wetlands can have alpha and gamma diversity on par with freshwater tidal wetlands (e.g., Sharpe and Baldwin 2009 in Chesapeake Bay, USA; Suchrow et al. 2015 in the Wadden Sea, Germany; and Watson and Byrne 2009 in San Francisco Bay, USA), but it is unclear whether those patterns were driven by rare or dominant v www.esajournals.org species. ...
Abstract Understanding patterns of biodiversity is a key goal of ecology and is especially pressing in the current human‐caused biodiversity crisis. In wetland ecosystems, human impacts are centered around hydrologic manipulation including the common practice of wetland diking and impoundment. Constraining how wetland management influences plant biodiversity patterns across spatial scales will provide information on how best to modify actions to preserve biodiversity and ecosystem function in managed wetlands. Here, we compare patterns of plant diversity and species presence, abundance, and community composition at several spatial scales among tidal wetlands along an estuarine salinity gradient and managed wetlands that were formerly tidal. Managed impounded wetlands had decreased alpha and gamma diversity of rare species, with less than 60% of the species richness found in tidal brackish wetlands at several spatial scales. There was little change in the overall pattern of alpha, beta, and gamma diversity for common species in impounded wetlands; however, dominant tidal brackish species, primarily perennial rhizomatous graminoids, were replaced with management target plants and non‐native annual grasses in impounded wetlands. This species replacement led to over 60% of impounded sites being classified as containing novel plant assemblages. An additional 25% of impounded sites were classified as containing tidal saline plant assemblages, suggesting potential soil salinization. Along the estuarine gradient, patchiness and codominance of common plant species drove high diversity and turnover in tidal brackish wetlands, while it remains unclear whether tidal fresh or brackish wetlands maximize rare plant diversity. With reduced species richness, altered functional dominants, and novel or saline assemblages, impounded brackish wetlands may require careful water management to balance native plant biodiversity, associated ecosystem processes, and waterfowl requirements.
... For example, increased flooding and salinity stress, whether from sea-level rise or other causes, have been shown to negatively affect plant biomass production, species richness, and the abundance of flood-intolerant species in a range of coastal marshes (Baldwin et al. 1996;Morris et al. 2002;Sharpe and Baldwin 2009;Goodman et al. 2011;Kirwan and Guntenspergen 2012;Neubauer 2013;Snedden et al. 2015). Increased flooding and salinity can also lead to shifts in species composition within tidal brackish and saline marshes (Baldwin and Mendelssohn 1998;Brock et al. 2005;Sharpe and Baldwin 2012), where salinity or flood tolerances often differ among co-dominant plant species (Pennings and Callaway 1992;Pennings et al. 2005;Touchette et al. 2009;Li et al. 2018). ...
Tidal marshes are increasingly vulnerable to degradation or loss from eutrophication, land-use changes, and accelerating sea-level rise, making restoration necessary to recover ecosystem services. To evaluate effects of restoration planting density and sea-level rise on ecosystem function (i.e., nitrogen removal), we restored three marshes, which differed in elevation, at Weeks Bay National Estuarine Research Reserve, Alabama, USA and planted them with Juncus roemerianus sods at 0, 25, 50, 75, or 100% initial cover. We simulated future sea level using passive weirs that increased flooding during low tide. Because additional species emerged shortly after transplantation, we also tested for treatment effects on community structure. In all marshes, species richness increased following restoration, regardless of treatments, while relative abundances of new species tended to increase with increasing initial cover. Plant percent cover increased with increasing initial cover in all marshes, with similar vegetated cover at 50, 75, and 100% after 3 years in the highest elevation marsh. Porewater dissolved inorganic nitrogen concentrations ([DIN]) decreased with increasing initial cover in all marshes, and were significantly lower in 50, 75, and 100% treatments than 0 or 25% after 1 year. Furthermore, [DIN] was similarly low among 50, 75, and 100% treatments when elevation capital was highest. These results suggest that intermediate initial cover (50%) can recover plant cover and promote nitrogen removal when elevation capital is adequate at relatively lower labor and material costs than planting at higher cover, thereby maximizing restoration outcomes in the face of low to moderate sea-level rise.
... Those 2 rivers had high life-form turnover, and they also had emergent, amphibious, submerged, and floating macrophytes. Sharpe and Baldwin (2009) and Weilhoefer et al. (2013) found that changes in habitat characteristics led to the replacement of macrophyte groups along spatial gradients in coastal wetlands in the northern USA. Thus, for the Itanhaém and Itapanhaú rivers, it is possible that variables related to longitudinal gradient influenced their life-form beta diversity by promoting habitat diversity that supports different groups of macrophytes . ...
Studies on beta diversity across different spatial scales can yield insight into the ecological factors that
shape communities and the mechanisms of maintenance and loss of diversity. The coastal rivers in southeast Brazil
have different lengths and salinity gradients because of variation in coastal plain width and slope. These differences
in environmental characteristics promote natural gradients and patterns of macrophyte assemblage variation
within and among rivers. To investigate the drivers of macrophyte beta diversity, we recorded the occurrence
of species and life forms and collected limnological variables at 100 sampling sites over 8 unconnected rivers that
run directly to the sea. We estimated macrophyte beta diversity, and its nestedness and turnover components,
within (local scale) and among (regional scale) coastal rivers using traditional metrics (Jaccard dissimilarity matrix)
and a metric that accounts for sampling effect (permutational analysis of multivariate dispersions). At each sampling site, we collected variables from water (nutrients, dissolved oxygen, and pH), sediment (nutrients, salinity,
and grain type), and channel (width, littoral declivity, distance from river’s mouth, and coastline). For assessment
of regional-scale drivers of macrophyte beta diversity, we measured river length and calculated salinity gradient.
We evaluated the potential of environmental variables to explain local and regional beta diversity using distancebased redundancy analysis and multiple linear regression. As expected, at the local scale, high species turnover and
life-form nestedness were predominantly explained by the rivers’ longitudinal gradients (mainly salinity, P, and
channel width). At the regional scale, we found that river length explained life-form nestedness among rivers (small
rivers are subsets of the largest rivers); however, neither river length nor salinity gradient explained the high species
turnover among rivers. We suggest that dispersal limitation among rivers and historical colonization shaped the
species pool in each river resulting in almost completely distinct assemblage compositions. This high turnover at
the regional scale suggests that conservation strategies for macrophytes must consider multiple rivers and not only
the largest ones. Overall, our results suggest that environmental variation strongly influences macrophyte beta diversity within and among coastal tropical rivers.
... While estuarine wetlands have been extensively studied, landscape-scale studies of the wetland complexes of major coastal rivers spanning the estuarine-to-tidal freshwater wetland gradient from river mouth to the head of tide are scarce, perhaps due to the persistence of interdisciplinary schisms noted by Odum (1988). Studies in the Chesapeake Bay region have documented wetland vegetation patterns along the estuarine gradient Baldwin 2009, Sharpe andBaldwin 2013). A few studies of narrower scope have encompassed both estuarine and tidal freshwater wetlands of tidal rivers; for instance, a review article from the Fraser River estuary of western Canada summarized localized wetland studies along the estuarine gradient (Adams and Williams 2004). ...
This paper describes the distribution and variability of wetland plant species (n = 203) on the 234 river-kilometer lower Columbia River and estuary floodplain. The plant data is coupled with elevation and hydrology data to develop a predictive model of species distribution that can be applied to restoration and changing environmental conditions.
... Effects of previous hurricanes on local water quality has been studied [16]; however, high resolution measurements comparing a wide range of parameters along a salinity gradient during a hurricane has not been well documented. These salinity gradients exist as transition zones for coastal systems that are greatly affected by climate change, sea level rise, and large scale disturbances such as hurricanes [27,28]. Thus, it is critical to understand the effects of disturbance events on these transition zones to determine the resilience of these systems. ...
Hurricanes cause landscape-scale disturbances that affect biogeochemical cycling and water quality in coastal ecosystems. During Hurricane Irma’s passage through northern Florida, water movements driven by wind velocities up to 105 km h−1 caused a salinity peak in an estuary/blackwater river complex. Water quality was monitored across the 15 km site to detect the magnitude and duration of disturbance. Saline water intruded 15 km inland into a freshwater portion of the river that peaked at a salinity of 2 psu. Due to the volume of precipitation from the hurricane, significant runoff of freshwater and dissolved organic matter (DOM) caused a decrease in salinity, dissolved oxygen (DO), and Chlorophyll-a concentrations while increasing turbidity and fluorescent dissolved organic matter (fDOM). The disturbance caused rapid changes observed by in-situ water quality monitors over a 3-week period, but some effects persisted for longer periods as shown by 3-month weekly water sampling. This disturbance caused shifts in DOM loading, altered salinity dynamics, and reshaped landscapes due to wind and wave surge both in upland marsh and downstream estuary. Hurricane disturbance temporarily and abruptly alters the aquatic continuum, and observations of system response can help us understand the mechanisms associated with ecosystem resilience and recovery.
... On the other hand, lower diversity index of wetland vegetation in middle points can be attributed to limited resource due to low flow velocity and higher cross-sectional area, which facilitated only a few dominant species like Chrysopogon zizanioides and Cynodon dactylon to survive (Friedman and Auble 2000;Wright et al. 2015). However, no significant differences in species richness among the sampling stations might be due to the high levels of disturbance that prevented occurrence of most species, preventing coexistence and reducing species richness (Sharpe and Baldwin 2009). On the other hand, flood phase wise, lowest species richness and diversity in the late flood phase of the wetland can be attributed to the increased nutrient loss and tissue damage of wetland vegetation due to increased disturbance as a result of increased flood fluctuation frequency (Bornette et al. 2008). ...
Hypothesis: Variation in species assemblages due to micro-topographic features and flow regime determine
vegetation carbon stock in floodplain wetlands.
Material and method: We tested this hypothesis in Chatla—a tropical floodplain wetland located in northeast
India. Five sampling stations characterized by contrasting micro-topographic and flow parameters were selected in
the wetland for study. Species composition, assemblage pattern, and vegetation carbon stock were studied in these
stations during three flood phases, i.e., early, middle, and late flood phases following standard methods. Univariate
and multivariate statistics were used to determine the relationship between the selected environmental parameters,
plant species assemblages, and vegetation carbon stock of the wetland.
Results: Thirty-one species of herbs and five species of shrubs were recorded from the five stations in Chatla
floodplain wetland. Flow regime characterized by water flow velocity and discharge showed substantial variations
across the stations. These parameters in turn are related to variations in the micro-topographic characteristics
namely depth, width, and cross-sectional area of the stations. Plant species composition and abundance differed
significantly with respect to micro-topography and flow regime as revealed by the cluster diagram. The canonical
correspondence analysis revealed strong association of plant species assemblages with the micro-topography and
flow regime within the wetland. Multiple regression analysis revealed a significant positive relationship of the
vegetation carbon stock with the water discharge.
Conclusions: Spatial variation in plant species diversity because of micro-topography and flow regime determines
the vegetation carbon stock in floodplain wetlands. Modification of these parameters by anthropogenic activities
such as mining and quarrying may potentially influence the carbon stocking potential of seasonal floodplain
wetlands. Therefore, appropriate measures should be taken to maintain the integrity of the natural topographic
features of such wetlands.
... Salinity fronts are also boundaries between distinct ecological habitats (Holligan et al., 1984). The ecological characteristics on either side of a frontal region are often substantially different because of species' preferences for different salinities (Kirst, 1989), contributing to the biological diversity of an estuary (Meire et al., 2005;Sharpe & Baldwin, 2009). Nekton often take advantage of the tidal propagation of fronts as well; Epifanio et al. (1984) found that crab larvae use the landward propagation of bottom fronts to preferentially migrate into Delaware Bay. ...
