Ammophila breviligulata
Encyclopedia
Ammophila breviligulata (American beachgrass or American marram grass) is a species of grass
that is native to eastern North America
, where it grows on sand dunes along the Atlantic Ocean
and Great Lakes
coasts. Beachgrass thrives under conditions of shifting sand, sand burial, and high winds; it is a dune-building grass that builds the first line of sand
dunes along the coast. Beachgrass is less vigorous in stabilized sand, and is only infrequently found further inland than the coastal foredunes. A. breviligulata was introduced to the Pacific coast of North America in the 1930s. It is proving to be invasive, and is increasingly important to coastal ecology and development in Oregon
, Washington, and British Columbia
.
The leaves of A. breviligulata have deeply furrowed upper surfaces and smooth undersides, and grow 2 to 3 ft (0.6096 to 0.9144 m) tall. The plant's inflorescence
is a spike-like panicle
that can reach 10 inches (25.4 cm) long; the seed head appears in late July or August. The species name breviligulata derives from the Latin brevis ("short") and ligula ("tongue"), which refers to a small feature of grasses called the ligule
.
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A. breviligulata is quite similar in appearance and ecology to a second species of beachgrass, Ammophila arenaria
(European beachgrass). As Nick Page has summarized, "Ammophila breviligulata is distinguished from A. arenaria by smaller ligules (1-3 mm versus 10-30 mm long in A. arenaria), wider and less inrolled leaves, longer flower spike (25-35 cm versus 15-25 cm long in A. arenaria), and scaly rather than puberulent leaf veins on the upper leaf surface."
s), and can produce up to 100 stems per clump annually. They can tolerate burial in as much as 3 feet (1 meter) of sand; sand burial stimulates the rhizomes to grow vertically, and is actually essential to plant vigor. The beachgrass species are also very good examples of xerophyte
s, being able to thrive on arid to semi-arid beach dune
s. The plant has several mechanisms for adapting to heat stress or wind. The long narrow leaves can roll or fold, and the rough upper leaf surface, which contains the gas exchange openings (stomata), can orient itself away from wind.
Beachgrass is a dominant species on foredunes, and indeed is sometimes the only plant found there. It is much less vigorous further in from the coastline, which is puzzling. Why should a species that competes so well on foredunes be fairly unsuccessful just a few meters further in from the coast, where other plants usually dominate? One mechanism for this effect that has been extensively studied by Wim van der Putten and his colleagues is based on the susceptibility of Ammophila species to soil pathogens such as nematode
s. The density of these pathogens is low in freshly deposited sand, but builds up in the roots of beachgrass on stabilized sand. While the details are complex, the result is that beachgrass is largely limited to the foredunes that it builds, which are immediately adjacent to water's edge and where sand is removed and redeposited fairly frequently.
north to British Columbia
), but along nearly every coast worldwide where it has been introduced. A. arenaria built foredunes (the dunes closest to the beach) that are typically about 14 feet (4.3 m) high, which is much higher than the dunes associated with the native dune grass species Leymus mollis
.
In the 1930s, A. breviligulata was introduced to about 3000 acres (1,214.1 ha) on the Clatsop Peninsula in Oregon
. Since then, A. breviligulata has gradually supplanted A. arenaria in Oregon and Washington; the precise reason for the relative success of A. breviligulata isn't known. The most recognizable aspect of the changeover between the beachgrass species is that the foredunes of A. breviligulata are shorter than the foredunes of A. arenaria; A. breviligulata's foredunes are about 9 feet (2.7 m) high in this region. The diversity of other species that co-exist with mature stands of A. arenaria is comparable to the species diversity with A. breviligulata. However, the lower foredune height for the latter means that coastal ecosystems that had adapted to the fairly tall foredunes of A. arenaria are again changing, especially in the regions just behind the foredune and sheltered by it. Similarly, buildings and roads that were constructed under the presumption of continuing protection by A. arenaria's tall foredunes may now be threatened by shifting sand and by increased exposure to wind and water in storms.
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
that is native to eastern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, where it grows on sand dunes along the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
coasts. Beachgrass thrives under conditions of shifting sand, sand burial, and high winds; it is a dune-building grass that builds the first line of sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
dunes along the coast. Beachgrass is less vigorous in stabilized sand, and is only infrequently found further inland than the coastal foredunes. A. breviligulata was introduced to the Pacific coast of North America in the 1930s. It is proving to be invasive, and is increasingly important to coastal ecology and development in Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, Washington, and British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
.
Botanical description
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
is a spike-like panicle
Panicle
A panicle is a compound raceme, a loose, much-branched indeterminate inflorescence with pedicellate flowers attached along the secondary branches; in other words, a branched cluster of flowers in which the branches are racemes....
that can reach 10 inches (25.4 cm) long; the seed head appears in late July or August. The species name breviligulata derives from the Latin brevis ("short") and ligula ("tongue"), which refers to a small feature of grasses called the ligule
Ligule
A ligule — is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges or a strap-shaped corolla, such as that of a ray floret in plants in the daisy family....
.
Ammophila arenaria
Ammophila arenaria is a species of grass known by the common names European Marram Grass and European Beachgrass. It is one of two species of the genus Ammophila . It is native to the coastlines of Europe and North Africa where it grows in the sands of beach dunes. It is a perennial grass forming...
(European beachgrass). As Nick Page has summarized, "Ammophila breviligulata is distinguished from A. arenaria by smaller ligules (1-3 mm versus 10-30 mm long in A. arenaria), wider and less inrolled leaves, longer flower spike (25-35 cm versus 15-25 cm long in A. arenaria), and scaly rather than puberulent leaf veins on the upper leaf surface."
Ecology
Both species of beachgrass are noted for their association with stable sand dunes, and observations in regions where they were introduced to coasts indicate that they actually build the first line of dunes on coasts (the foredunes). The plants spread rapidly (6 to 10 ft (1.8 to 3 m) annually) through the sand by subsurface runners (rhizomeRhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s), and can produce up to 100 stems per clump annually. They can tolerate burial in as much as 3 feet (1 meter) of sand; sand burial stimulates the rhizomes to grow vertically, and is actually essential to plant vigor. The beachgrass species are also very good examples of xerophyte
Xerophyte
A xerophyte or xerophytic organism is a plant which has adapted to survive in an environment that lacks water, such as a desert. Xerophytic plants may have adapted shapes and forms or internal functions that reduce their water loss or store water during long periods of dryness...
s, being able to thrive on arid to semi-arid beach dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
s. The plant has several mechanisms for adapting to heat stress or wind. The long narrow leaves can roll or fold, and the rough upper leaf surface, which contains the gas exchange openings (stomata), can orient itself away from wind.
Beachgrass is a dominant species on foredunes, and indeed is sometimes the only plant found there. It is much less vigorous further in from the coastline, which is puzzling. Why should a species that competes so well on foredunes be fairly unsuccessful just a few meters further in from the coast, where other plants usually dominate? One mechanism for this effect that has been extensively studied by Wim van der Putten and his colleagues is based on the susceptibility of Ammophila species to soil pathogens such as nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s. The density of these pathogens is low in freshly deposited sand, but builds up in the roots of beachgrass on stabilized sand. While the details are complex, the result is that beachgrass is largely limited to the foredunes that it builds, which are immediately adjacent to water's edge and where sand is removed and redeposited fairly frequently.
Invasiveness on the Pacific coast of North America
Starting in the 19th Century, A. arenaria was introduced to the Pacific coast of North America to help control beach sands; it serves this role so well that it is now considered invasive not only along this coast (from CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
north to British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
), but along nearly every coast worldwide where it has been introduced. A. arenaria built foredunes (the dunes closest to the beach) that are typically about 14 feet (4.3 m) high, which is much higher than the dunes associated with the native dune grass species Leymus mollis
Leymus
Leymus is a genus of the true grass family . The common name for this genus is "wild rye"; however, members of the genus Elymus are also sometimes given the same common name...
.
In the 1930s, A. breviligulata was introduced to about 3000 acres (1,214.1 ha) on the Clatsop Peninsula in Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
. Since then, A. breviligulata has gradually supplanted A. arenaria in Oregon and Washington; the precise reason for the relative success of A. breviligulata isn't known. The most recognizable aspect of the changeover between the beachgrass species is that the foredunes of A. breviligulata are shorter than the foredunes of A. arenaria; A. breviligulata's foredunes are about 9 feet (2.7 m) high in this region. The diversity of other species that co-exist with mature stands of A. arenaria is comparable to the species diversity with A. breviligulata. However, the lower foredune height for the latter means that coastal ecosystems that had adapted to the fairly tall foredunes of A. arenaria are again changing, especially in the regions just behind the foredune and sheltered by it. Similarly, buildings and roads that were constructed under the presumption of continuing protection by A. arenaria's tall foredunes may now be threatened by shifting sand and by increased exposure to wind and water in storms.