Monatane-Grassland Ecosytem

Description

2.1 Description
The montane grassland ecosystem is distinguished from other types of ecosystems by its physiognomy, floristic composition and ecology. It consists of herbaceous stratum usually not higher than 30 – 80 cm, very rich in perennial grasses and species of Cyperaceae, but also with sub-shrubs and perennial herbs, among which bulbous and rhizomatous plants occur (Pichi-Sermolli, 1957). The original climax vegetation on the montane grassland of Ethiopia was supposed to be a dry evergreen montane forest intermingled with small areas of grassland (Zerihun Woldu, 1988). According to White (1983), the montane grassland of Ethiopia is a derived vegetation type, although small areas of the grassland may have existed before human settlement.

The monotony of this grassy sward is braked by scattered shrubs or trees, usually rather small. In places the shrubs form clusters or thickets in the shelter of which larger herbs may occur. The change from montane grassland to evergreen thicket and scrub is often abrupt in places where the flat ground meets a steep slope also.

This ecosystem occurs in the areas where human activity has been largest and most intense, and found at altitudes between 1500 and 3000 m.a.s.l. The montane grassland in most places derived from forest and other woody vegetation types. The relict patches of forest associated with the grassland ecosystem consists of species of Juniperus procera, Olea europaea sub sp. cuspidata and Afrocarpus falcuatus (Zerihun Woldu, 1988). The environmental factors determining the variation in vegetation types in the montane grassland ecosystem are moisture, topography and human activity.

Characteristic species of the montane grassland ecosystem include species of: Pennisetum shimperi, Pennisetum glabrum, Pennisetum mezanu, Hyparrhenia rufa, Cynodon dactylon, Eragrostis tennifolia, Eragrostis japonica, Pennisetum clandestinum, Panicum maximum, Cymbopogon spp. Chloris spp., and Andropogon spp. (Tewolde Berhan Gebre Egziabher, 1988). The various types of grass species are interspersed with trees such as Acacia abyssinica, Acacia nigri, Prunus africana, Juniperus procera, Olea europaea, Allophylus abyssinica, Celtis africana, Croton macrostachyus, Milletia ferruginea, Measa lanceolata, Buddelja polystachia, Erythrina brucei, Myrsine africana, Calpurnia aurea, Dovyalis abyssinica, Draceana afromontanum. Besides these growth forms shrubby species such as Acokanthera shcimperi, Carissa edulis, Rosa abyssinica and Maytenus arbutifolia (Zerihun Woldu, 1988).

Since this ecosystem is densely occupied by humans and, therefore, highly disturbed. As aresult, the wildlife resource is extremely poor. Except for some Hyaenas and Golden Jackal, bird species such as Wattled Ibis, Olive thrush and others.

The Ethiopian highlands are resulted from volcanic activities of tertiary. Vast areas rose up in that is now the eastern half of Africa, and this up rise was more marked in the central plateau. As a result of tectonic movements the basaltic-trappian series formed high plateau landscape due to successive flows (Zerihun Woldu, 1988; Mohr, 1971). With regard to soils, the montane grassland occurs on vertisol and areas with high internal drainage. According to Ochtman and Berhanu Debele (1976) the soil in central highlands of Ethiopia is predominantly phaeozems also nitosol occur in some places.

The montane grassland ecosystem occupies part of the Ethiopian highlands, which are climatically designated as warm temperate climate with most of the precipitation in the summer (Koppen, 1923). The region has distinct periods of rainfall maximal while the intervening periods are variable. The main rainy period is from the end of June to mid October, which accounts for about 70-85 % of the total rainfall (Zerihun Woldu, 1988).

The second rainy period which usually lasts for some weeks only falls between the last week of March and first week of May. The major source of the big rain is usually the Gulf of Guinea, whereas the source for the small rain is the Indian Ocean (Daniel Gemechu, 1977). The seasonality of the rainfall distribution is explained by the position of the ITCZ (Inter Tropical Convergence Zone).

Ditribution

2.2 Distribution
The montane grassland ecosystem occurs on extensive gently undulating highlands of Ethiopia at altitudes between 1500 – 3000 m a.s.l. (Pitchi-Sermolli, 1957). The grassland vegetation is mainly interspressed with relict patches of forest indicating remnants of past human disturbance. This ecosystem occur on the uplands of central Shewa; North and Western Shewa, Arsi, North portion of Bale and Borana highlands, highlands of western and Eastern Hararge Zones in Oromia region; Highlands of East and West Gojam, highlands of South and North Gonder, North Shewa and parts of North and South Wello zones in Amahara region; Highlands of eastern Tigray; highlands of Sidamo zone, Gamo Gofa in southern region.

Diversity

2.3 Species diversity
Study on diversity of plant species in montane grassland ecosystem was restricted to few studies such as Zerihun Weldu (1988), Friis (1992) and White (1983). Zrihun Weldu (1988), provided extensive list of grasses in grasslands in central Shewa.

Uses,Values

2.4 Uses and values
The most important value of the montane grassland of Ethiopia is linked to subsistence agriculture such as crop production and livestock husbandry, since this ecosystem is relatively more hospitable to human. The bulk of the Ethiopian’s food comes from small scale farming (over 80%) which in good year produce surplus for marketing. Major crops cultivated in this ecosystem are annuals such as Teff (Eragrostis teff), Wheat, Barley, Horse bean, and Pea, Linseed. Livestock raising is also a foundation for the social, cultural economic structure of the society since livestock are investments, drought, transport as well as sources of food items.

The wide valleys on the plateau are on seasonally waterlogged black clays (vertisols), which are unsuitable for the growth of trees and other woody plants. Grass is well adapted to grow naturally on such soils and these areas have been called edaphic grasslands. The edaphic grasslands are most important grazing areas for the domestic animal of the highland peasant farmers. It should be noted that Ethiopia has the highest domestic animal population in Africa and the tenth highest in the world.

Plant species grown for specific purpose also include Eleusine coracana, which is used in making of local beverage. Hyparrhenia rufa is used for construction of thatch roof. Eleusine flocafolia and Pennisetum sphacelatum are also used in the making of household crafts.

In addition to the mentioned uses, considerable areas in the montane grassland ecosystem are set aside for tree plantation purposes to meet the fuel wood and construction material consumption. Eucalyptus spp. are mainly utilized for such purposes.

Threats

2.5 Threats and rates of Change
Agricultural practices are expanding at the expenses of the destruction of the natural vegetation and the deterioration of the natural environments in general. Crop cultivation is practiced even at slopes more than 45 %, irrespective of the low yields to be expected at this type of ecosystem (Hedberg, 1986).

Studies have indicated that the livestock density in this ecosystem is more than 3 times the carrying capacity of the grasslands (Zerihun Woldu, 1988). Therefore, there is a considerable habitat and land degradation in this ecosystem.

The extreme heavy land-use on the steep mountainous grassland of Ethiopia, which has remained unchanged over several centuries, is a degraded landscape in many places. Generally the effect of excessive vegetation harvest, overgrazing, and intensive farming is aggravated by the rugged topography with steep slopes lead to severe soil erosion (Zerihun Woldu, 1988). The heavy vegetation destruction coupled with high amount of rain in July and August, lead to the transport of much of the fertile soil.

Human encroachment and resource utilization in the mountain grassland of ecosystem is mainly influenced by demographic and strategic political factors, imposed significant pressure on the land productivity potential. The extensive agriculture system has currently replacing the montane grassland ecosystem to intense farm area, urban settlement and other developments.

Status

2.6.Conservation status
If montane grasslands have been protected from over grazing, intense fire, and in general intensive utilization, the habitat could be changed to forest precursor, shrubs, small trees and climbers that may form thickets. However, there have no significant conservation measures, which have been carried out. The very nature of the landscape and hospitality of the montane grassland encouraged high human settlements and therefore, it was not possible to set aside any protected or managed area for conservation. However, it is possible to undertake integrated land-use planning with environmental conservation activities at landscape level.

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