Salt silt grass

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Salt silt grass
Salt mud grass (Spartina anglica) in the tidal area of ​​the Wadden Sea

Salt mud grass ( Spartina anglica ) in the tidal area of ​​the Wadden Sea

Systematics
Commelinids
Order : Sweet grass (Poales)
Family : Sweet grasses (Poaceae)
Subfamily : Chloridoideae
Genre : Silt grass ( Spartina )
Type : Salt silt grass
Scientific name
Spartina anglica
CEHubb.

The Spartina anglica ( Spartina anglica C. E Hubb. , Syn .: Sporobolus anglicus (CEHubb.) PMPeterson & Saarela ), also called English cord grass called, is a fertile (fertile) hybrids . It belongs to the sweet grass family (Poaceae). Originally only widespread ( endemic ) in south-central British shore regions, it was planted on many coasts as a sand and silt catcher and has been spreading rapidly since then. As a so-called invasive species , it has a multitude of direct and indirect ecological effects on other species, communities or biotopes in the Wadden Sea habitat .

Taxonomy, origin and routes of spread

The hybrids Spartina × townsendii and Spartina anglica originated on the English Channel coast . While the parent species Spartina alterniflora (2n = 62) comes from North America , Spartina maritima (2n = 60) is native to southern England . From the species mentioned, the sterile (sterile) hybrid Spartina × townsendii (2n = 61) emerged, which in turn became Spartina anglica (2n = 122) through chromosome duplication ( autopolyploidization ) .

Spartina alterniflora was first discovered in southern England in 1816. The seeds were probably brought to the English coast by ships in the ballast water . In 1870 the sterile hybrid Spartina × townsendii was found there. In 1892 a new fertile silt grass species was described for the first time, which was later named Spartina anglica .

In the Wadden Sea, rhizome parts of the salt silt grass were planted for targeted land reclamation . These were first imported from England to the Netherlands in 1924 , to Germany in 1927 and to Denmark in 1931 . Starting from these plantings, the silt grass spread independently over drifted rhizome parts and seeds. Their current distribution is therefore a combination of anthropogenic and natural distribution. The taxon is considered a prime example of the rapid, recent evolution of species.

Salt mud grass ( Spartina anglica )

distribution and habitat

The salt silt grass occurs sporadically to widespread in the entire tidal area of ​​the Wadden Sea (Netherlands, Germany, Denmark). Its main occurrence is along the mainland coast and on the islands on the sides facing the mainland. It is originally native to England, but occurs as a neophyte in Ireland , northern France , New Zealand , Australia , China and in the USA in the states of Washington and California .

Due to its high tolerance to flooding and salt, the silt grass can grow furthest along the mean water line (MThw) and occurs here in the samphire zone . In areas with very calm water, it can build up dense, closed stands; when the waves strike, only smaller areas or only individual clumps arise. On the land side, it also penetrates salt marshes and estuaries . Because of its occurrence in near-natural vegetation, it is considered an agriophyte . The salt mud grass is a character species of the Spartinetum anglicae from the Spartinion association, but also occurs in the Puccinellietum maritimae from the Puccinellion maritimae association.

description

The salt silt grass is a perennial , herbaceous aquatic plant with overwintering buds under water ( hydrophyte ) that reaches heights of between 30 and 130 cm and grows in dense clumps with thick, fleshy rhizomes .

The bare stalks are surrounded by leaf sheaths along their entire length . The ligule is replaced by a wreath of silky hair about 2 mm long. The gray-green leaf blades are 8 to 50 cm long and 6 to 15 mm wide. They grow steeply upright and are drawn out into a very thin, hard point. The tops are heavily ribbed and the edges are sharp-edged rough.

The panicles of two to nine spike-like branches are yellow-green, up to 20 cm long, upright and contracted. The anthers with fertile pollen are 8 to 12 mm long. The flowering period extends from July to October. From the sterile Townsends siltgrass ( Spartina × townsendii ) the salt siltgrass can be distinguished by the shape of the fruit , a caryopsis , and the longer anthers (5 to 8 mm) with sterile pollen.

Biology and ecology

The salt siltgrass is a pioneer plant . It multiplies via rhizome fragments and seeds that are spread via the water. Through shoots , individual plants develop very dense clumps that are very resistant to mechanical effects. The salt excretion through salt glands is very effective in this salt plant (halophyte). A salt gland in salt mudgrass consists of only two cells. For one thing, there is a large basal cell. With its cell wall, it borders directly on the neighboring cells of the leaf tissue. There is no separating cuticle. The other cell is the smaller secretion cell. It is assumed that mainly sodium ions are excreted here. The leaves are very resistant due to the inclusion of silica . When submerged, a film of air forms on its furrowed surface, which facilitates gas exchange when submerged. This allows the silt grass to tolerate flooding for up to 16 hours.

Status and effects of the spread

The World Conservation Union ( IUCN ) has included Spartina anglica in its list of the “100 of the World's Worst Invasive Alien Species”. The Federal Agency for Nature Conservation (BfN) has grass on the list of invasive species occurring in Germany. A total of 32 species are currently listed here. The spread of the salt silt grass has a variety of effects.

Environmental impact

The salt silt grass has a variety of ecological effects in the Wadden Sea. This includes the establishment of a "new" plant society - the silt grass society of the Spartanietum anglicae . This is a persistent and very species-poor initial society of the Wadden Sea.

The settlement of salt silt grass is associated with the displacement of less competitive species and with negative consequences for soil organisms and microfauna due to the dense root system (loss of habitats). It replaces the stocks of the mud flats ( Salicornia stricta ) in the samphire zone ( Salicornietum ), which can be found on near-natural and natural locations of the coastal waters. The penetration of the silt grass in salt marshes is more difficult. Due to its high and dense growth, it displaces the salt marsh plants in the Andel zone ( Puccinellietum maritimae ). Andel lawns can become more humid due to the silt grass because it hinders the drainage of the water.

Its large biomass enters the food chain almost exclusively as detritus . For plover species (Limikolen or waders) valuable feeding grounds are lost on open tidal flats. This has resulted in a decrease in bird populations in estuaries of up to 50% in the UK. The dunlin ( Calidris alpina ) was particularly affected .

Sedimentation and erosion, economic effects

The silt grass was originally planted on the North Sea coast to promote land reclamation (definition of the sediment) . However, it did not live up to expectations as it did not form sufficiently large, closed stands and spread to areas where the sediment was already set. While closed stands in the mean water area can strongly promote sedimentation, individual nests lead to local scouring through vortex formation . How the changes in sedimentation and erosion affect coastal protection is generally unclear, so that the economic consequences cannot be accounted for.

Human health

Ergot on silt grass

The plant, although non-toxic itself, is a host for the ergot fungus Claviceps purpurea . More recent studies by the Leibniz University of Hanover showed a strong infestation of the panicles of the salt silt grass with Claviceps purpurea for the North Sea coast . The wintering organs of this fungus, the sclerotia called ergot , are highly poisonous and contain higher concentrations of ergot alkaloids in silt grass than in cereals; even the consumption of some of them can lead to death in young children. Since the silt grass has also spread to pastures in the entire foreland of the dike, according to a botanist from the University of Hanover, sheep and dogs or even children could be affected. The exact distribution has not yet been clarified, but ergot has also been found in the silt grass in the Netherlands and Denmark. Spokespeople for the National Park Administration and the Lower Saxony Chamber of Agriculture, on the other hand, consider a threat to people or animals to be unlikely and have so far seen no concrete evidence. The infestation is known and so far limited to the lower part of the salt marshes, which is a nature reserve.

Mudflat hikers can cause painful cuts on the sharp leaves.

Hazard potential and measures

Further consequences of the spread of salt silt grass and their dangers, especially for coastal protection, are still largely unexplained. The effects of the infection of the silt grass with the Spartina mottle virus (SpMV) and the fungus Claviceps purpurea are also unknown . The latter has led to a decrease in silt grass seed production in England.

In Germany, no control measures have been carried out to date, as observations of the development of the stocks so far do not justify such. Experience in other countries shows that small stocks can be removed without any problems. There is evidence from England and the USA that mowing appears to be a suitable means of preventing seed setting and thus further spread. In the long run, this should displace the silt grass. In Washington, after mowing, silt grass was covered with foil. After one or two growing seasons , the plants died. Tearing up and digging up the grass, on the other hand, does not appear to be very promising because rhizome fragments remain in the ground and sprout again. A closer observation ( biomonitoring ) of the development of the silt grass population is being discussed in specialist circles .

credentials

further reading

  • Ingo Kowarik : Biological Invasions. Neophytes and Neozoa in Central Europe. Ulmer, Stuttgart 2003, ISBN 3-8001-3924-3 , p. 234ff.
  • Stefan Nehring: Alien species in the North Sea. Invasion success and climate warming. In: Ocean Challenge. 13, 3, 2003, ISSN  0959-0161 , pp. 12-16.
  • Karsten Reise: The silt grass Spartina anglica. The invasion of a new kind. In: Jose L. Lozán, Eike Rachor, Karsten Reise, Jürgen Sündermann, Hein Westernhagen (eds.): Warning signals from the Wadden Sea. Scientific facts. Blackwell, Berlin et al., ISBN 3-8263-3025-0 , pp. 211-214 ( Blackwell expertise ).

Web links

Commons : Salt siltgrass ( Spartina anglica )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Rafaël Govaerts (ed.): Spartina anglica. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved November 18, 2016.
  2. ^ Erich Oberdorfer : Plant-sociological excursion flora for Germany and neighboring areas . With the collaboration of Angelika Schwabe and Theo Müller. 8th, heavily revised and expanded edition. Eugen Ulmer, Stuttgart (Hohenheim) 2001, ISBN 3-8001-3131-5 , pp.  239 .
  3. ^ Künnemann, Gad: Salzwiesen , Isensee Verlag 1997, pages: 23ff., ISBN 3-89598-414-0
  4. ^ AF Raybould, AJ Gray and RT Clarke: The Long-Term Epidemic of Claviceps purpurea on Spartina anglica in Poole Harbor: Pattern of Infection, Effects on Seed Production and the Role of Fusarium heterosporum , In: New Phytologist , Vol. 138, No. . 3, Mar., 1998, http://www.jstor.org/stable/2588346
  5. ↑ Toxic ergot spreads in the North Sea. Report at Scinexx.de / Leibniz Universität Hannover , May 22, 2013.
  6. ↑ Ludger Fertmann: Dangerous parasite on the Wadden Sea. Article in Die Welt on May 23, 2013
  7. ↑ dradio.de, Forschung Aktuell , May 28, 2013, Michael Engel: Ergot on the coast - fungus attacks silt grass on the North Sea (May 30, 2013)