Andropogon gayanus
Andropogon gayanus, commonly known as gamba grass, Rhodesian blue grass, tambuki grass, and other names, is a species of grass native to most of the tropical and subtropical savannas of Africa.
History and naming
Andropogon gayanus was recognised and named by 1833. Its common names include gamba grass, bluestem ; Rhodesian andropogon ; Rhodesian blue grass ; onga, tambuki grass ; and sadabahar.Description
This tufting perennial bunchgrass can grow tall and in diameter, and has hairy leaves. Most of its roots are fibrous, spreading close to the surface of the soil for up to, but it also has thick cord roots which store starch and anchor the plant as well as vertical roots able to extract water from a greater depth during the dry season.It produces large numbers of light, fluffy seeds, which can be spread by wind, animals or machinery. It spreads rapidly where vegetation is disturbed, but most seeds fall within of the parent plant.
Habitat
The grass is native to most of the tropical and subtropical savannas of Africa, also extending southwards into Mozambique, Botswana, Namibia and South Africa in regions with long dry seasons. It occurs naturally in xerophytic grasslands on doleritic, sandy or clay soils, at altitudes of up to, and is very drought-tolerant. However it does not do well where mean minimum temperatures dip below 4.4 degrees Celsius, and it is not frost-tolerant. It has also been introduced around the world as a pasture crop in Australia and Brazil.Uses
A. gayanus was introduced as a pasture crop in many parts of the world, including Australia, tropical countries of the Americas, as well as naturalising in Brazil It has also been introduced in Nigeria to reclaim land that has been overgrazed.Strips of the grass are also planted in millet fields help to reduce wind erosion of the soil.
In some African countries, the stems are also used as thatch and for making pen.
Environmental impacts
Gamba grass forms dense patches, out-competing native species and altering ecosystems. Areas of dense infestation have a significantly higher fire risk than native pastures. It is highly resistant to both cutting and fire, and ungrazed tussocks can generate very intense fires, leading to loss of tree cover and long-term environmental damage. It replaces native grasses, reducing natural biodiversity on ungrazed land. Being highly invasive, it can move into conservation areas, semi-urban residential land and mining leases.This has led to its declaration as a noxious species, officially being declared a "Weed of national significance" in Australia since 2012. Western Australia, the Northern Territory, and Queensland all have state legislation which prohibits planting of new plants and requires land managers to control infestations.