Impact de pollutions ponctuelles sur les phytocénoses des rivières acides à neutres du Limousin (Massif Central, France)

L'impact des pollutions ponctuelles sur les phytocénoses aquatiques est étudié autour des rejets de 12 agglomérations dont 9 sont équipées d'une station d'épuration. Un échantillonnage systématique avec segmentation du cours d'eau autour de chaque rejet est réalisé. Sur chaque secteur, des relevés de végétation sont pratiqués au niveau de faciès d'écoulements homogènes dont on caractérise le milieu physique parallèlement à une analyse physicochimique de l'eau.L'ensemble des rejets provoque globalement une élévation de la conductivité, des teneurs en ammonium, nitrates et orthophosphates.Cela ce traduit par la régression de la phytocénose à Callitriche hamulata et Myriophyllum alterniflorum, par le développement de Ranunculus peltatus, Callitriche platycarpa et d'espèces cryptogames telles que Leptodyctium riparium, ou Melosira sp.Une Analyse en Composantes Principales menée sur l'ensemble des données permet d'opposer des phytocénoses propres aux secteurs amonts (Scapania undulata, Chiloscyphus polyanthus) à d'autres situées au niveau de rejets (Callitriche platycarpa, Leptodictyum riparium, Melosira sp.,).Une Analyse Canonique de Correspondances valide le déterminisme de la qualité physicochimique de l'eau sur la végétation. La conductivité, les teneurs en ammonium, nitrates et orthophosphates deviennent prépondérants par rapport aux facteurs du milieu physique classiquement discriminants dans l'installation des phytocénoses dans les rivières limousines.The impact of located pollution on aquatic phytocénoses is studied around 12 cities discharge. Nine of them are fitted out purification plant.The sampling method is based on consecutive segments from upstream to downstream. On each sector, vegetation records are realized in homogeneous water runoff facies, which are characterized by physical factors as well as water value measures.The whole discharge leads globally to an increase of conductivity, ammonium amount, nitrates and orthophosphates. The consequence of that is a decrease of Callitriche hamulata and Myriophyllum alterniflorum phytocénoses, a development of Ranunculus peltatus, Callitriche platycarpa and cryptogams species like Leptodictyum riparium or Melosira sp.A Component Principal Analysis applied on data, distinguishes phytocénoses belonging to upstream sectors (Scapania undulata, Chiloscyphus polyanthus) from the ones of discharges (Callitriche platycarpa, Leptodictyum riparium, Melosira sp.).A Canonical Correspondence Analysis validates the impact of physico-chemical water quality on vegetation. Conductivity, ammonium amount, nitrates and orthophosphates become more preponderant in comparison with physical environments usually discriminant for phytocénoses installation in Limousin rivers

Variations écologiques et chorologiques de la végétation macrophytique des rivières acides du Massif armoricain et des Vosges du Nord (France)

La végétation macrophytique des rivières acides d'Europe occidentale présente une grande unité, marquée par la constance d'un ensemble floristique de base, dont certaines espèces (Callitriche hamulata, Myriophyllum alterniflorum, Potamogeton polygonifolius, P. alpinus, etc) sont propres à ces eaux acides, d'autres (Callitriche platycarpa, Sparganium emersum, Elodea canadensis, Potamogeton crispus, etc) étant communes avec les eaux calcaires.Cet ensemble subit des variations écologiques et chorologiques :L'augmentation du niveau trophique des eaux conduit d'une végétation oligotrophe (différenciée par P. polygonifolius, Juncus bulbosus, etc) à un groupement mésoeutrophe (caractérisé par Callitriche obtusangula, Nasturtium officinale, etc). Ainsi, quatre types de phytocénoses ont pu étre distingués dans les Vosges du Nord en fonction de ce paramètre. D'autre part, une pollution organique localisée, par exemple par une pisciculture en Bretagne, provoque une augmentation des espèces eutrophes (C. obtusangula) et une régression des taxons plus oligotrophes (Scapania undulata).L'alternance de biotopes courants et lents se traduit par un remplacement de phytocénoses : ainsi, en Bretagne, Oenanthe crocata et Ranunculus penicillafus sont associées sur les radiers, alors que Nuphar lutea et S. emersum caractérisent les mouilles. De plus, une diminution de l'éclairement permet la présence de groupements bryophytiques spécifiques.Les principales variations chorologiques entre les deux territoires correspondent à un enrichissement des zones atlantiques en macrophytes euatlantiques ou méditerranéoatiantiques, comme O. crocata ou Apium inundatum, qui manquent dans les régions médioeuropéennes. En outre, selon les territoires biogéographiques, l'écologie de certaines espèces peut varier (par exempte S. emersum, R. peltatus, P. polygonifolius).Les macrophytes permettent donc, à l'instar des invertébrés benthiques, l'élaboration de biodiagnostics des eaux courantes.For the study of the vegetation of acid rivers in France, two areas have been investigated by the authors : Armorican Massif and Northern Vosges (fig. 1).This paper has two aims :- assessing the general trends of macrophytic vegetation : floristic composition and plant communities, with special reference to the influence of physical and water quality parameters,- pointing out and interpreting the variations observed between the two regions (chorological differences), and in the watercourses (ecological variations).Floristic data and phytosociological surveys (from bryophytes to angiosperm macrophytes) were collected along 50 m. stretches (at least) by the stratified sampling method in the case of large watercourses, and by systematic surveys for smaller ones. Consecutive 50 m. long sketches were used to measure the effect of localized pollution. (The inventory is as precise as possible). A distinction was made between the aquatic communities and river-bankside ones. At the same time, physical parameters were measured or observed (depth, light conditions, width,...), certain water-quality parameters were measured (pH, conductivity,...) and water samples were collected for further analysis.The data collected are gathered and compared in a table (table 1) showing differences between aquatic and subaquatic species, and between sunlit and shaded stretches. Trophic tendencies of most species are given according to either our observations or the literature.The main ecological feature is the streaking longitudinal variation of aquatic species, which agrees with the zones described by ILLIES and BOTOSANEANU : crenon, rhitron and potamon. In sunlit areas the succession is dominated by the following species :Potamogeton polygonifolius, Juncus bulbosus, Glyceria fluitans,...-> Ranunculus spp., Callitriche hamulata, Myriophyllum alterniflorum,...     ->Potamogeton crispus, Elodea canadensis,...Areas in the shade are characterized by bryophyta; the succession is : Scapania ondulata->Rhynchostegim riparioïdes, Fontinalis antipyreticaAs for the aquatic species, a longitudinal succession of bankside species exists :Sparganium erectum, Carex paniculata, Carex rostrata->Phalaris arundinacea      ->Phalaris arundinacea, Typha latifoliaThe macrophytic vegetation in acid rivers of Western Europe shows a great homogeneity, marked by the constancy of a floristic list, in which some species (Callitriche hamulata, Myriophyllum alterniflorum, Potamogeton polygonifolius, Potamogeton alpinus, Scapania undulata, etc.) only grow into acid waters, while others species (Callitriche platycarpa, Sparganium emersum, Elodea canadensis, Potamogeton crispus, etc.) grow also in calcareous waters.This basic unit is submitted to ecological and chorological variations.Ecological variations are due mainly to changes of the water quality. They are illustrated by two examples :- two river systems in the Northern Vosges where a general survey shows longitudinal variations of communities without pollution or assessing different kinds of pollution,- a pisciculture pollution with observations of species distribution on consecutive sketches.An increase of water trophic level leads progressively from an oligotrophic vegetation (marked by Potamogeton polygonifolius, Juncus bulbosus, etc.) to a meso-eutrophic community (characterized by Callitfriche obtusangula, Nasturtium officinale, etc.). Four communities are distinguished in Northern Vosges (table 2) and characterize water quality (both pollution and trophic level) :A : Potamogeton polygonifolius, Juncus bulbosus, Sphagnum spp. community, with the following main water-quality parameters : conductivity : 40-80 µS, phosphates : 500 ppb N).Two vegetation maps show the distribution of these communities (fig. 2). The succession of communities is related to water quality and fastened sequences are compared to normal ones. Without any pollution, A and B communities caver more than 5 km along the upper streams; under these conditions, the entire sequence A to D develops to 15 km, while with much anthropic pollution, it may occur within less than 3 km. A heavy pollution leads to the leads of communities as observed with the change tram A to C (without any B) due to a camping-site.A localized organic pollution by a Breton pisciculture is responsible for water-quality changes (table 3): ammonia, nitrites, phosphates and conductivity increase. The succession of mineral nitrogen forms is assessed (fig. 3). In the N-NH4+ and N-NO2- peak areas, the eutrophic species increase (Callitriche spp., specially Callitriche obtusangula, Amblystegium riparium) and the oligotrophic ones decrease (Scapania undulata) (fig. 3). Tissue analysis of Ranunculus penicillatus and of Callitriche spp. does not show any enrichment in nitrogen in polluted areas: the ecological response is mainly an increase of nitrophilous macrophytes (Callitriche spp.).The influence of water quality is more obvious in the Northern Vosges for most of the oligotrophic communities grow in forested sketches, white in Brittany these conditions are rare and eutrophication occurs in all the streams, even in the source areas. Floristically, neutrophilous or ubiquitous species are numerous. Some of them indicate either eutrophication or pollution : Amblystegium riparium and perhaps Octodiceras fontanum for bryophyta, Callitriche obtusangula, Potamageton perfoliatus and Sparganium. emersum (long leaves form), for aquatic species, Nasturtium officinale, Glyceria maxima for helophytes.Physical parameters also lead to variations. The succession of swift and slow areas leads to changes in the communities. Thus, in Brittany, Oenanthe crocata and Ranunculus penicillatus are associated on the riffles, while Nuphar lutes and Sparganium emersum characterize the pools, even in the upper parts of the streams where there are watermill ponds.The relationships between local hydrodynamic features and species distribution are discussed with regards to the stretches around the pisciculture area.Main chorological variation is an enrichment of atlantic areas with numerous eu-atlantic or mediterraneo-atlantic species : Porella pinnata and Amblystegium fluviatile as bryophyla, Oenanthe crocata, Apium inundatum, Ranunculus omiophyllus as spermaphyta. As there are few or no species restricted to medio-european areas, Atlantic communities are often richer than eastern ones. But some invading species as Elodea nuttallii are spreading all over the country from North-Eastern France.Ecological trends of certain species (Sparganium emersum, Ranunculus peltatus, Potamogeton polygonifolius) can change between the two biogeographical areas. So, Sparganium emersum grows in the upper oligotrophic zones in Northern Vosges while it characterizes lower meso-eutrophic zones in Brittany. In Brittany, Ranunculus peltatus un exist in eutrophic areas when the stretches are far from the sea. Potamogeton polygonifolius is very rare in swift streams in Brittany.Therefore, macrophytes permit, as benthic invertebrates do, to get a river biodiagnosis. They are easily observed and mapped so they can be used for a general survey

Flow measurements around a submerged macrophyte patch in an in-situ flume setup

In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distribution and aquatic plant abundance. Recently, local differences in hydrodynamic conditions have been shown to be an explanatory mechanism for the patchy pattern of Callitriche platycarpa Kütz. vegetation in lowland rivers. Those patches are often subject to strong hydrodynamic forces as they act as a resistance against the current. A plant‟s ability to tolerate water movement without suffering mechanical damage often relies on minimizing the hydrodynamic forces by avoiding stress. In this paper, we have quantified the behaviour and influence of a C. platycarpa patch in an in situ flume, manipulating the incoming discharge on a single patch. The knowledge obtained helps to understand the plant-flow-sediment interactions that form the basis of the explanatory mechanism for the patchy vegetation pattern

Hilfe zum Sammeln und Bestimmen von Arten der Gattung Callitriche (Wassersterne)

Die Wassersterne (Callitriche L.) zählen ungeachtet der Fortschritte in der Bearbeitung der Gattung nach wie vor zu den problematischen Arten, welche in der Bestimmungsarbeit hinreichend Erfahrung voraussetzen. Das schlägt sich auch im Bearbeitungsstand nieder. In der Mehrzahl der Florenlisten und Florenwerke wird deshalb vornehmlich auf eine Artdiagnose verzichtet, oder es sind die Aussagen mit Vorbehalt zu übernehmen. So zeigt es sich, daß unbelegte Angaben nicht verwertbar sind. Um für das Kartierungsvorhaben zum Florenatlas von Sachsen-Anhalt ausreichend Material verwerten zu können, sei hier eine Anregung zum Sammeln und Bestimmen der Gattung gegeben

Die Wassergüte der Nette

Für die Beurteilung der Wasserqualität der Nette erwiesen sich insbesondere folgende Indikatoren als geeignet: Permanganatverbrauch, %-Sättigung, O2-Gehalt, BSB5 - Wert, Ammonium, Nitrit, Nitrat, Phosphat, Chlorid, Sulfat und der Wasserpflanzenbestand. Im quellnahen Oberlauf weist die Nette die Güteklasse II auf. Durch Streusiedlungen und den Abfluß einer Tierkörper-Verwertungsanstalt verschlechtert sich die Qualität bis auf III-IV; danach steigt sie wieder auf III bzw. II-III an

Threatened vascular flora of León province

De los más de 2800 taxones que integran la flora vascular leonesa, 200 se han incluido en esta Lista de la Flora Leonesa amenazada. De ellos 61 forman parte de la Lista Roja de la Flora Vascular Española (que previamente sólo recogía 49 para León). Hemos catalogado hasta el momento 30 taxones vulnerables (VU) y 3 en peligro (EN). Los otros 28 están incluidos en la categoría «datos insuficientes» (DD). Incluimos en este trabajo además otros taxones que por sus peculiaridades pueden considerarse de interés; entre ellos, 38 con una sola población en León y, por ello, sometidos en este territorio a cierto grado de amenaza.The León flora includes more than 2800 taxa, from which we include some two hundred (200) in the Red List of the Leon Flora. 61 of them belong to the Red List of the Spanish Vascular Flora (only 49 formerly). From the 61 taxa, we have labelled 30 as Vulnerable (VU), 3 as Endangered (EN), and 28 as «with Deficient Data» (DD). In this paper, we include also other taxa that can be considered as interesting because of their peculiarities, like 38 taxa showing a sole population in León province, and thus threatened in some degree within this territory

Macrophytes aquatiques dans les bras morts du Rhin et du Main en Hesse

Zur Schließung von Kenntnislücken zur Flora der Gewässer Hessens wurden 2009 von der BVNH neun Altarme von Rhein und Main untersucht. Die Ergeb-nisse zeigen, dass viele als sehr selten oder verschollen geltende Gewässermakrophyten noch oder wieder in den Altarmen des hessischen Oberrheinabschnitts zu finden sind. Insgesamt wurden 51 Arten nachgewiesen, darunter fünf Armleuchteralgen.In 2009, the flora in eight oxbow lakes along the Hessian stretch of the River Rhine and in one oxbow lake along the Hessian stretch of the River Main was surveyed by the Botanical Society for Nature Conservation in Hesse. Several rare species were recorded, some of which had not been recorded for decades. Altogether, 51 species were recorded, including five charophytes.Pour combler les lacunes dans la Flore aquatique en Hesse, la Société botanique pour la conservation de la nature en Hesse (BVNH) a étudié en 2009 neuf anciens bras du Rhin et du Main. Les résultats ont dévoilé que de nombreux macrophytes aquatiques, considérés comme très rares ou même disparus, sont encore présents ou sont réapparus dans les bras morts de la section supérieure du Rhin en Hesse. En tout 51 espèces ont pu être prouvées dont cinq charas

Vodeno bilje Hrvatske: Podaci proizašli iz herbarijske zbirke ZA

As many as 963 herbarium sheets featuring 76 aquatic plant taxa from the ZA collection were digitised and published online through the Virtual Herbarium. Aquatic plants have been collected over a period of 176 years, with three peaks (second decade of the 20th century, in the 1940s and 1950s, and in the current decade). Most of the specimens were collected in Croatia and a smaller number in neighbouring and geographically close countries. The importance of the collection is expressed through the specimens of many rare and threatened species, because it represents the only evidence of their presence in Croatia (the regionally extinct Caldessia parnassifolia, as well as Luronium natans, Callitriche platycarpa, C. truncata, C. hermaphroditica, Potamogeton alpinus, P. compressus, P. polygonifolius, Nuphar × spenneriana and Sparganium minimum). The collection in ZA is a valuable source of data about the historical and recent distribution of aquatic plants that constitute a foundation for the estimation of distribution changes, threat assessment and conservation policies.Digitalizirana su 963 herbarijska lista 76 vodenih biljnih svojti iz zbirke ZA, te je omogućen javni pristup ovom materijalu putem online portala Virtualnog herbarija. Vodeno bilje sakupljano je u razdoblju od 176 godina, s tri maksimuma (u drugom desetljeću 20. stoljeća, tijekom 1940-ih i 1950-ih, te tijekom recentnog desetljeća). Većina biljaka je sakupljena na području Hrvatske, a manji dio u susjednim i zemljopisno bliskim državama. Važnost zbirke očituje se u značajnom broju rijetkih i ugroženih vrsta, za koje je zbirka jedini dokaz njihovog postojanja u Hrvatskoj (regionalno izumrla Caldessia parnassifolia, zatim Luronium natans, Callitriche platycarpa, C. truncata, C. hermaphroditica, Potamogeton alpinus, P. compressus, P. polygonifolius, Nuphar × spenneriana i Sparganium minimum). Zbirka vodenog bilja u ZA vrijedan je izvor podataka o povijesnoj i recentnoj rasprostranjenosti vrsta, što je temelj za procjenu promjene areala vrsta, procjenu ugroženosti te njihovu zaštitu

Flow-divergence feedbacks control propagule retention by in-stream vegetation: the importance of spatial patterns for facilitation

Facilitation (enhancement of propagule retention in this case) is increasingly recognized as an important driver of biodiversity, but it is still unknown if facilitation during dispersal and colonization is affected by self-organized spatial pattern formation. We investigated the ability of in-stream submerged macrophyte patches to trap the vegetative propagules of three species (<i>Berula erecta</I>, <i>Groenlandia densa</i>, <i>Elodea nuttallii</i> in two size classes: 13–22 and 40–48 cm long), and to potentially benefit the colonization of these three species. We tested the effects of propagule traits, hydrodynamic forcing, and spatial patch configuration on propagule trapping. Propagule buoyancy was negatively correlated with trapping chance, while propagule size did not influence trapping. Species-specific differences in buoyancy were maintained for weeks after fragmentation. Propagule retention was interactive and conditional upon the interplay between incoming flow velocities and vegetation spatial patterning. In the flume experiment at low flows, a patchy configuration (one patch filling 66% of the flume width) retained more surface-drifting propagules (<i>B. erecta, G. densa</i>), than near-homogeneous cover (two patches close together, filling the entire flume width). In contrast, retention of sinking <i>E. nuttallii</i> propagules increased in the two-patch configurations. In flume and field releases where patches did not completely fill the channel width, water flowed around the patches rather than over or through them. This resulted in low-flow velocity areas within patches where canopies were upright and propagules were retained, and higher velocity flows around patches. In contrast, when vegetation filled the channel width, water could not be diverted laterally around the patches and preferentially flowed over them, causing the canopies to bend and reduce their trapping capacity. In flume experiments at high flows, retention of all species decreased, regardless of vegetation configuration, as propagules passed over the reconfigured vegetation canopies. These findings on the interplay of water movement and patch reconfiguration suggest that environmental heterogeneity generated by the self-organizing behavior of aquatic plants might enhance colonization of sessile organisms, calling for landscape-scale processes like dispersal to be better investigated