Grasses Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns and ...

are one of the most abundant

floras Flora is all the plant life present in a particular region or time, generally the naturally occurring (indigenous) native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' gut flora'' or '' skin flora''. E ...

on all continents, except

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

. Their

divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the quantity of the vector field's source at each point. More technically, the divergence represents the volume density of the ...

is estimated to have taken place 200 million years ago. Humans have intentionally and unintentionally introduced these species to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

through travel and trade. On the North American

plains In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands. In ...

prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s, and

meadow A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifi ...

s at least 11% of grasses are non-native. North America is considered a hotspot for many

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

of grasses, which threatens all of the endangered native grass species and potentially threatens other grass species. Conservation tactics and management policies can help prevent invasive species from taking over and driving native North American plants to extinction.

Attributes

Non-native grasses are classified as invasive if they have the following three attributes: # The grass must have a pathway to be delivered to a new location, e.g. boat, shoe, animal, vehicle, feed, contaminated seed, etc. # It is able to tolerate its new environment long enough to establish and reproduce. # It is able to coexist with native plants. Invasive grasses can outcompete native plants species by manipulating environmental conditions through either chemicals or other physiological factors. These factors give an upper hand, which will allow the invader to outcompete the native plants. For example, a study conducted in the

Mojave desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

by Smith ''et al.'' in 2006, found that invasive grass species increase in areas with higher concentrations of

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

(CO₂), especially in arid conditions which make up 20% of Earth’s terrestrial surface area. Therefore, the annual invasive grasses will outcompete the natives because they use CO₂ to their advantage.

Impacts

There are many impacts involving invasive grasses in North America, which range from an ecosystem level to a community level to a genetic level. Such impacts influence habitat structure, disturbance regimes, and nutrient cycling. A successful invasion of a grass may result in new hybrid species, which can have both good and bad results. A good result could be a new species. A bad result could produce a sterile species, which would eventually lead to the extinction of that grass. European

Cheatgrass ''Bromus tectorum'', known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southe ...

invading the North American prairies is an example of a disturbance regime because it burns quickly and is very susceptible to fire. As a result, it gives invasive grasses a head start in the reproduction process. Another invasive grass impact example, at the ecological level, is

Cordgrass ''Spartina'' is a taxon of plants in the grass family, frequently found in coastal salt marshes. Its species are commonly known as cordgrass or cord-grass, and are native to the coasts of the Atlantic Ocean in western and southern Europe, north ...

or more specifically ''

Spartina anglica ''Sporobolus anglicus'' (common cordgrass) is a species of cordgrass that originated in southern England in about 1870 and is a neonative species in Britain. It was reclassified as '' Sporobolus anglicus'' after a taxonomic revision in 2014,Pe ...

''. This species arose in England as an

allotetraploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...

of two wild species and was introduced intentionally, to control erosion on the coasts of North America. It now flourishes spreading across the mudflats of the Pacific coast changing them into

salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated ...

es, which has tremendous effects on the fauna of the mudflats such as clams, worms, and anemones.

Management

In order to keep North American native grasses from potentially going extinct from invasive grasses, it is important to control or better yet prevent such invasions in the first place. There are many ways to go about this such as controlling species mechanically or physically. This includes hand removal of grasses or by machine. In a five-year study conducted by Wilson ''et al.'' (2001) in Western Oregon, showed that mowing prairies of the invasive grass

Arrhenatherum elatius ''Arrhenatherum elatius'', with the common names bulbous oat grass, false oat-grass, tall oat-grass, tall meadow oat, onion couch and tuber oat-grass, is a species of perennial grass, native to Europe, western Asia, and northern Africa. This bun ...

allowed the native grasses

Danthonia californica ''Danthonia californica'' is a species of grass known by the common name California oatgrass. This plant is native to two separate regions of the Americas, western North America from California to Saskatchewan, and Chile. Description ''Danthonia ...

and Festuca roemeri to flourish and out compete the non-natives. This is an effective method for the control of invasive grasses but it will take many hours of hard manual labor, which could be costly. Using chemicals is an effective way to control non-natives but it is not very ecologically friendly. Chemicals such as herbicides can contaminate waterways or kill other plants in the immediate area. Biological control is the use of other organism to reduce the invader grass. This has been proven to be effective but has also ricocheted back in a negative way. Other options include using multiple approaches at the same time, for example, mowing a specific region of grass land and then using an herbicide to target the invasive. The ultimate way to control invasive grasses in North America is to prevent them from entering in the first place. The first step of this prevention is identifying and regulating the grasses' pathway. After that it needs government assessment and policies to see that these pathways are blocked or regulated.

References

{{Reflist

External links

California Invasive Plant InventoryEvolutionary Genetics of Invasive SpeciesIncreased genetic variation and evolutionary potential drive the success of an invasive grass
Grasses of North America Lists of graminoids

Grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...