THE LEUCAENA LEUCOCEPHALA SPECIES AND ITS NEGATIVE IMPACT ON THE ENVIRONMENT
The Leucaena leucocephala is listed as a weed in Brazil, Agentina and in Bolivia. In this place, the species is taken as serious invader in the Islands of Fernando de Noronha. The species spread all over the tropical and sub-tropical parts of the world. Leucaena leucocephala is one of the plants that are promoted by international agroforestry organisation. It was promoted for food purpose, because it produces nutritional food for livestock. The foliage and seeds of Leucaena leucocephala contains the amino acid called mimosine (Matthews and Brandt 2006). The mimosine acid is very poisons to other plants which lead to invade the riverbanks, roadsides, cultivated land, and forest margin and in waste land.
During 16 century Leucaena leucocephala again introduced into Philippines for the purpose of feeding the ruminant livestock. Now it is spread all over the pacific region of Asia where it is previously used as agroforestry. This plant is easily propagated from seeds but it may grow from cutting. Its seeds are dispersed by vertebrates’ animals such as birds and rodents. Now this species is not planted at all in Asia. Leucaena leucocephala is a slow growing tree especially when it grows in high altitude.
Leucaena leucocephala is a small thornless tree or shrub that can reach a height of 10m tall. In its home environment Leucaena leucocephala prefers to grow on coastal sands and on shallow limestone soils. This plant prefers many different types of soils because their roots systems allow it to tolerate many soils types. The Leucaena leucocephala can grow fast with a fertile clay soils (James A.D, 1983). It can grow in alkaline and saline soils and in area where there is low phosphorus and iron in soils. It can not grow in place where flood takes more than three weeks. Leucaena leucocephala prefers to grow with an optimal temperature of approximately 25 to 30 degrees Celsius.
The mature plants of Leucaena leucocephala are well adapted to fire and it can regrow from the burnt stumps. It is easily generate from basal shoots after fire (Lam, 2006). Leucaena leucocephala is a drought tolerant but it is poor adapted to infertile acidic soils. It also prefers to live in disturb areas like, along the road.
In its home environment the Leucaena leucocephala typically occurs as dense thicket forming. It is difficult to mitigate (eradicate) the L. leucocephala as it grow as a dense thicket forming. The glucoside mimosine produced by the seeds and leaves of L. leucocephala cause a problem with the hair of young cattle and horses in places where it introduced. Subspecies leucocephala is particularly precocious and free seeding.
It is concluded that L. leucocephala is accidentally introduced in South Africa by international agro forestry organisation. This organisation introduced this species because it produces the nutrition food for livestock. Unfortunately they are not aware that, this species produce mimosine acid which is very poisons to other species. The acid produced by the seeds and leaves of L. leucocephala destroy the forest margin and cultivated area in South Africa. This species threaten the biodiversity of South Africa because it has the possibility to spread over a long distance. The glucoside mimosine produced by the seeds and leaves of L. leucocephala destroy the hair of young cattle and horses.
The following methods can be used to eliminate the spreads of L. leucocephala species; Biological, Chemical and mechanical methods. A mechanical method involves the removal of invasive species using machines or hands. This method is most useful to eliminate the invasive species. Cutting or burning of L. leucocephala can be applied. This method is mostly useful at the beginning of the year.
Chemical method may also used. This method is used to prevent the spreading of L. leucocephala. This method involves the use of herbicides and pesticides. Herbicides can be used to destroy the L. leucocephala. It allows the person to cut down the stem of L. leucocephala and apply hebicides. Biological control method can be used. This methods is mostly useful to stop the spread of L. leucocephala by releasing new species. All this methods can be used to eliminate the spreads of L. leucocephala. Chemical and mechanical methods are the best methods to eliminate alien species as compared to biological methods.
James A.D.1983. Handbook of Energy Crops.[Online].[Cited, 23 January 2007].Available from:http://www.hort.purdue.edu/newcrop/duke_energy/Leucaena_leucocephala.html
Lam, D.W, 2006 Leucaena leucocephala [Online].[Cited, 23 january 2007].Available from: http://www.hear.org/pier/species/leucaena_leucocephala.htm
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