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ABSTRACT: The spread of the invasive native clonal grass Elymus athericus is one of the most significant changes that have affected the plant communities of European salt marshes in the last decade.
The goal of this study was to investigate the rate of this invasion and its impact on C cycling in a non-grazed salt marsh
of the Mont Saint-Michel Bay (France). Aboveground net primary production (ANPP), litter quantity and quality, and decomposition
rates were quantified in Elymus athericus and in the original plant communities (“control”). Since 1991, Elymus athericus has been replacing the characteristic plant communities at a rate of 4 ha yr−1. ANPP was significantly higher in Elymus athericus (3011±347 gDW m−2 yr−1 and 1181±123 gC m−2 yr−1) than in the control (2028±239 gDW m−2 yr−1 and 771±76 gC m−2 yr−1) stands. Lignin content of Elymus athericus’ litter was 3.5 times greater than in the litter of the control communities, explaining its accumulation under the vegetation
(i.e., litter quantity was from 2 to 10 times greater under Elymus athericus than under the control vegetation). C mineralization in the sediment (expressed as rate of CO2 per mass of sediment) was significantly lower under Elymus athericus than under the control vegetation. Our results suggest that Elymus athericus increased C trapping within the salt marsh and thus limits the potential for C exportation toward coastal waters.
Wetlands 04/2012; 24(2):268-276. · 1.34 Impact Factor
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ABSTRACT: The current U.S. wetland mitigation policy of "no net loss" requires that a new wetland be created to replace any natural wetland destroyed under development pressures. This policy, however, may be resulting in a net loss of carbon-based wetland functions. We evaluated the ability of created wetlands to accumulate carbon and to mitigate loss of carbon-based functions in natural wetlands with variable hydrology. Potential limiting factors to carbon accumulation within created systems included soil aggregation, texture, and bulk density. Rates of soil development and the time required for created wetlands to accumulate the amount of carbon found in natural wetlands were estimated by an exponential model. Soils collected from five created (ages 3-8 years) and four natural freshwater marshes, located in central Ohio, USA, were analyzed for soil organic carbon (SOC), mineralizable soil carbon (Cmin), water-stable aggregates (WSA), particle-size fractions (PSD), and bulk density. Peak-standing aboveground plant biomass was also quantified. Created wetlands contained significantly less plant biomass, SOC, and Cmin than natural wetlands (c < 0.05; false discovery rate). Soil physical properties also differed significantly between created and natural wetlands, with fewer macroaggregates, more microaggregates, more silt-clay (0-5 cm only), and higher bulk density in created wetlands (a < 0.05; false discovery rate). Carbon content was positively correlated with macroaggregate content and negatively correlated with microaggregate content, silt-clay fraction, and bulk density. Fit of SOC data to the exponential model indicated that a newly created wetland would require 300 years to sequester the amount of SOC contained in a natural wetland. At this rate of carbon accumulation, a mitigation ratio of 2.7:1 (area) would be necessary for successful mitigation over a 50-year time period. However, other trajectories fit the data equally well and suggested area mitigation ratios of 2.2:1 (logistic) to 4.4:1 (linear regression) to 5.1:1 (exponential regression). Whether created wetlands are on a trajectory toward natural wetland carbon function, however, remains uncertain. Until gaps in the data are filled and a trajectory verified, the best mitigation policy will be a conservative one, with a restrictive permitting process and high mitigation ratios (5.1:1 minimum).
Ecological Applications 03/2010; 20(2):539-53. · 5.10 Impact Factor
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ABSTRACT: The effects of disturbance and microtopography on the organization and dynamics of plant communities were studied in a European salt marsh located in the Bay of Mont St. Michel, France. The existence of seed trapping mechanisms was also tested. The study took place in the lower and middle marsh plant communities dominated by the perennials Puccinellia maritima and Halimione portulacoides, respectively and associated with the annual Suaeda maritima. Three treatments were used in series of plots placed in each community: (1) vegetation removal and root destruction to a depth of 10 cm and refilling, (2) non-remnant herbicide treatment without vegetation removal and (3) creation of depressions (20 cm deep). These treatments were compared with adjacent control plots. The first year of the experiment showed that the perennials facilitated the establishment of Suaeda by trapping its seeds. Estimation of cover, density and biomass over 5 yr following the disturbances showed that in the first 2 yr Suaeda dominated the disturbed plots. Thereafter Suaeda was gradually eliminated by competitive exclusion after ca. 3 yr in the zone originally dominated by Puccinellia maritima and after 4 yr in the zone occupied by Halimione portulacoides. Depressions constituted refuge habitats for Suaeda by limiting competition with the perennials but also led to a high risk of mortality with temporal fluctuations in density. Despite a period of investigation limited to 5 yr, our study demonstrated that natural disturbances of various types occurred and influenced the dynamics of Suaeda, Halimione and Puccinellia. We deduced that natural disturbances and microtopography are responsible for the maintenance of the habitat in a state of non-equilibrium by favouring the establishment of both spatial and temporal environmental heterogeneity. These conditions appear to be particularly favourable for the maintenance of annual species such as Suaeda maritima.
Journal of Vegetation Science 02/2009; 13(1):115 - 122. · 2.77 Impact Factor
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ABSTRACT: The blind source separation and sound source localization based on independent component analysis on time-frequency domain considering time lag information between source signals and observation signals are conducted. The formulation based on the independency of time-frequency domain and the linearity of source signal is presented. The method which can be conducted not only the separation of source signals but also the specification of location of source signals is proposed through the consideration of time lags. Using this method, it can be analyzed even if observation signals include an intermittent noise, under the assumption of some independency of source signals. First of all, the number of source signals is specified through the quotient of complex valued time-frequency information of two observation signals. Next, the locations of source signals are specified using the relationship of relative time lags between source signal and observation signal. Then, the source signals are obtained by use of the Fourier information. The numerical test is conducted to confirm our method, and then the locations of source signals and source signals are obtained by high accuracy.
The Journal of the Acoustical Society of America 06/2008; 123(5):3303. · 1.55 Impact Factor
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ABSTRACT: Most plant diversity-function studies have been conducted in terrestrial ecosystems and have focused on plant productivity and nutrient uptake/retention, with a notable lack of attention paid to belowground processes (e.g., root dynamics, decomposition, trace gas fluxes). Here we present results from a mesocosm experiment in which we assessed how the richness of emergent macrophyte functional groups influences aboveground and belowground plant growth and microbial-mediated functions related to carbon and nitrogen cycling, with an emphasis on methane (CH4) efflux and potential denitrification rates. We found that an increase in the richness of wetland plant functional groups enhanced belowground plant biomass, altered rooting patterns, and decreased methane efflux, while having no effect on aboveground plant production or denitrification potential. We hypothesize that the greater root production and increased rooting depth in the highest diversity treatments enhanced CH4 oxidation to a relatively greater degree than methane production, leading to an overall decrease in CH4 efflux across our plant functional group richness gradient.
Ecology 12/2007; 88(11):2903-14. · 4.85 Impact Factor
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ABSTRACT: We experienced a case of paraurethral leiomyoma in a 36-year-old woman. She had been complaining of dysuria. She had noticed the presence of a mass in anterior vagina. That mass was about 3 x 3 cm, floating moderately firm with a smooth face sited in a paraurethral region. Magnetic resonance imaging showed medium-signal intensity on T1-weighted images and a homogeneous low signal on T2-weighted images. We diagnosed it as a paraurethral leiomyoma and enucleated it by surgery. At histological examination the tumor resulted in being a leiomyoma. The diagnosis and the treatment of female paraurethral leiomyoma are discussed.
Hinyokika kiyo. Acta urologica Japonica 10/2004; 50(9):661-3.
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ABSTRACT: Until 1979, European salt marshes were known only through the inventories of fauna and especially of flora. On such criteria, the salt marshes of the Mont-Saint-Michel bay (France) were regarded as most significant of the French coasts. However, it took 20 years of research on the role of these wetlands of the estuaries-salt marsh systems to highlight the ecological, social and economic interest of this ecotone, between continental and marine systems, a long time considered as territory "without value", except for stock breeders or hunters.
Comptes Rendus Biologies 09/2003; 326 Suppl 1:S125-31. · 1.53 Impact Factor
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ABSTRACT: The effects of sheep grazing on plant community structure and diversity were studied in saltmarshes of the Mont-Saint-Michel bay. This study took place at two scales: (1) at the scale of the entire bay to explore the changes in plant community over a ten year period; and (2) locally with the use of experimental exclosure set up to mimic the abandonment of grazing. Moderate grazing generally enhanced plant richness and diversity, while the absence of grazing and overgrazing lead to a decrease in diversity and richness. The development of management strategies is becoming critical to preserve the diversity of saltmarshes functions.
Comptes Rendus Biologies 09/2003; 326 Suppl 1:S148-57. · 1.53 Impact Factor
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ABSTRACT: The macrotidal Mont Saint-Michel bay has beenstudied intensively since 1990. The objectives ofthis study, supported by the European Union, wereto understand various processes underlying thefunctioning of this hydrosystem with a special focuson organic matter and nutrient fluxes betweensaltmarshes and marine waters. This paper presents asynopsis of these studies. The tidalflats are unvegetated and primary production isexclusively due to microphytobenthos communitiesdominated by diatoms. Halophile plant communitiescolonize the top parts of the tidal flats. Theircomposition and production vary according to amaturity gradient and sheep grazing. In ungrazedsaltmashes, production ranged from 1080 gDW m-2yr-1in the lower marsh to 1990 gDW m-2yr-1in the upper marsh whereas it was only 200 to500 gDW m-2yr-1in Salicorniaspp.dominated pioneer zones and sheep grazed areas. Mostof this organic matter (OM) was trapped in situ,processed by fungi and bacteria, and then releasedseaward via tidal fluxes, groundwater and runoff as particulate OMand nutrients: –497 kg N, –1200/–1000 kg P-PO4and –9900/–4200 kg inorganic carbon). A small amount ofOM was exported to the bay as macrodetritus. Fattyacids and stable isotopes, used as markers, showedthat OM produced by the marsh halophytes contributedto the diet of all the tidal flats invertebrates thatwere studied. Transient fish species were shown tocolonize the saltmarshes to forage or graze, exporting about 50 tons POM (DW)y-1. Therefore,it is assumed that the saltmarsh production enhancesthe production of the whole bay. But the functioningis still poorly known because the nutrient sinks havenot all been identified. Part of the nutrients inputwas provided by precipitation (+327 kg y-1), butthe contribution of the catchments was not quantifieddespite the fact that their influence was shown by thepresence of lindane in all the compartments of thesystem. Dynamics of saltmarshes are mainly influencedby natural sedimentation (1.5 million m3y-1in the bay), plant community succession, and management (i.e., reclamation and agricultural activities).
Wetlands Ecology and Management 01/2000; 8(2):147-161. · 1.43 Impact Factor
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ABSTRACT: Because of an excess of sedimentation due to natural and anthropogenic causes, the Mont Saint Michel (France) is becoming less frequently surrounded by seawater during high tide events. This prestigious monument and its bay have both been recognized by multiple national and international institutions for cultural and ecological richness. Diverse human activities such as tourism, fisheries, and farming also occupy the Mont Saint Michel Bay. The French government has been faced with a challenge of preserving the integrity of the bay, while restoring the ‘insularity’ of what used to be an island, the Mont Saint Michel. The objective of this paper is primarily to demonstrate how environmental scientists and ecologists influenced a typical civil engineering project and modified it into a civil/ecological engineering project, more respectful of both environment and human interests. To achieve this objective, we first retrace the formation of the Mont Saint Michel Bay, under both geological and historical perspectives, to provide the necessary background for the understanding of the actual restoration project. Some of the first projects that were proposed were designed to destroy the area of salt marshes that surrounded the Mont Saint Michel, with no consideration for the ecological integrity of the site. We conclude by presenting the current project in which France will invest over 130 million USD in the next few years. If this final project cannot be recognized truly as an ecological engineering project, it has the merit of being a compromise between various partnerships which have been debating for more than a century.
Ecological Engineering. 18(5):593-606.
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ABSTRACT: Chemistry was determined of sediments accumulated during flood pulses at a 5-ha bottomland hardwood forest located at the Olentangy River Wetland Research Park (ORWRP) in central Ohio. In the spring of 2000, hydrology was restored at forest by breaching the levee. Flat sediment traps (30 x 30 cm2) were used to collect sediment samples during spring/summer flooding events from 2003 to 2005. We investigated sediment chemistry (major elements) for: Al, B, Ca, Cu, Fe, K, Mg, Mn, Mo, Na, S, P, Zn. Al and Fe dominate the sediment chemistry and results show the elemental abundance in order of Al > Fe > Ca > K > Mg > S > P > Na > Mn > Zn > B > Cu > Mo. Correlations between Al (%) to other elements are positive with 0.95, 0.89, 0.84, 0.69, 0.67, 0.66, 0.59, 0.42 for B, Ca, K, Mn, Fe, Mo, Na, Cu respectively, while negative with 0.03, 0.50, 0.56 for P, Zn and S. Nineteen flooding pulses occurred between 2003 and 2004. Pulsing events may accelerate biogeochemical processes from flooded sediment to surface soils. Restoration of seasonally flooded bottomland forests could stimulate potentially large nutrient and Fe releases, which would eventually lead to enhanced forest productivity and biodiversity.
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ABSTRACT: Primary production and the detritus pathway (i.e., detritus production, litter fall, export to coastal waters, and decomposition) were studied over a 1-year period in three salt marsh levels (low, middle and high marshes). Carbon and nitrogen content in biomass and macro-detritus were estimated at each step of the detrital pathway. Several lines of evidence suggested that low, middle and high marshes had different properties which affected their interaction with adjoining waters. More than species diversity, the salt marsh zonation across a 1.8 km transect resulted in a spatial and temporal heterogeneity in the distribution of organic matter and nutrients within the salt marsh. The low marsh was the less productive level (1080 g dry weight m−2 per year) and was a source of organic matter for the two other marsh levels. Almost 89% of the organic matter produced in the low marsh was flushed away by the tide and redistributed inside the marsh, whereas the remainder decomposed quickly (0.023 per day) at the production site. The export of macro-detritus to coastal waters was probably insignificant to the carbon and nitrogen balance of the salt marsh. In the middle and high marshes, most of the production fell as litter directly at the production site. In the high marsh, vegetation stands were very productive (1990 g dry weight m−2 per year) and litter decomposed slowly (0.0047 per day). The middle marsh was as productive as the high marsh (1910 g dry weight m−2 per day), but the decay rate (0.028 per day) was similar to that estimated for the low marsh. This study demonstrates that the mineralization of halophyte-derived organic matter takes place almost completely within the marsh itself. Data on carbon and nitrogen decay indicated that only a small part of the high marsh production was rapidly available to fuel food webs of the ecosystem or to be exported to coastal waters. In contrast, the high amount of biomass produced in the middle marsh was rapidly available for food webs. Export of organic matter may be controlled by macro-detritus production (amount and timing), intensity and time distribution of tide events, and, mostly, decay rates. Because for most of the year the marsh is exposed to the atmosphere, we suggest that exchanges of gaseous carbon and nitrogen with the atmosphere should be investigated.
Aquatic Botany.
