Diversity of Ecosystems Ethiopia is endowed with diverse ecosystems in which diverse flora and fauna as well as microbial resources are found. The major ecosystems include: Afroalpine and subafroalpine, Montane dry forest and scrub, Montane moist forest, Acacia-Comiphora woodland, Combretum-Terminalia woodland, Lowland humid forest, Aquatic, wetland, Montane grassland, and Desert and semidesert ecosystems. Afroalpine and Sub-Afroalpine Ecosystem 1.1Description The areas which on the average higher than 3200 meters above sea level (m.a.s.l) are generally referred to as the Afroalpine and Subafroalpine (Hedberg, 1957). The lower limit of the afroalpine belt falls at about 3500 m, while the upper limit of vascular plants lies around 5000 m (Hedberg, 1964), and subafroalpine areas ranges between 3200- 3500 m. These areas include chains of mountains, mountain slopes and tops of highest mountains in the country. The highest peak in Ethiopia is Ras Dashen (4533 m a.s.l), where an alpine climate near 0°C persists all year round, sometimes even with a snow cover lasting a couple of days (Hurni and Ludi, 1998). However, dry lowland savannas and deserts surround this moist highland area. Ethiopia has the largest extent of afroalpine habitats in Africa (Yalden, 1983). The highlands of Ethiopia were formed between 40 and 25 million years from the present by lava outpouring of the trappian series in the Miocene and Oligocene (Mohr, 1971). The mountains are volcanic in origin dominantly overlie Precambrian basaltic and trachytic bedrocks. Moisture is not limiting, since most of these mountains attract much rain, and there is excessive internal drainage as the basaltic and trachytic bedrocks percolate water (Ensermu Kelbessa et al., 1992). However, at the upper alpine belt soil moisture could be limiting as water stays in form of heavy frost or ice and snow for prolonged time, and thus the amount of soil water available is the most important factor influencing the distribution of plant. Due to the increasing population pressure there are frequent encroachments by man that result in widespread destruction of wildlife and their habitats. Friis and Sebsebe Demissew (2001), further noted that intensive human pressures on the mountains is probably one of the major reasons for the discrepancies between the maps, and different interpretations of the vegetation types by the different authors. Comparatively there are more floristic and faunal studies from the afroalpine and subafroalpine ecosystems of Bale and Simien Mountains than from the same ecosystems of other regions such as Wello, Gemgofa, Arsi, etc. In a series of publications Hedberg (1962, 1964, 1975, 1986 and 1992) made important analyses on the vegetation and ecology of afroalpine regions in Ethiopia. Weinert (1981); Weinert and Mazurek (1984), Uhlig (1988) and Uhlig (1991) also made ecological investigations on the vegetation of the Bale Mountains. Miehe and Miehe (1994) made a detailed study on ericaceous vegetation and plant communities within the ericaceous zones of the Bale Mountains. Yalden (1985 and 1988) made studies on the small mammals of the Bale Mountains. Sillero-Zubiri and Gottelli (1994); Sillero-Zubiri et al. (1997); Sillero-Zubiri and Tattersall (1995 a, b) have made extensive ecological investigations on an Endemic mammalian species, Ethiopian wolf. There is now a shift of interest from Bale and Simien Mountains to the high massifs of central highlands and Wello (Zelealem Tefera, 2001). Blower (1966) proposed for the establishment of National Park in the Simien Mountains. Hurni and Messerli (1981); Hurni (1982, 1983, 1986, 1995), and Hurni and Ludi (1998) made series of studies in the Simien Mountains. Faunal studies mainly on rodents from the high mountains of Ethiopia were undertaken by Afework Bekele et al. (1993), Baskevich et al. (1993) and Afework Bekele (1995). An endemic and threatened species of mammal, Walia Ibex, which is restricted only to the Simien Mountains National Park was largely studied by Nievergelt (1970 a, b; 1971, 1981 and 1996). Many other studies that are not included in the above citing are still focused on the Bale and Simien Mountains, and generally detailed and long-term researches are scant. Therefore, there is a huge gap of knowledge regarding the biodiversity compositions and status of many of the high mountains of Ethiopia. The climate of Afroalpine ecosystem is governed by two fundamental geographical circumstances: the vicinity to the equator, and the high altitude above sea level (Hedberg 1964). Seasonal variations in climate are less important than the diurnal ones. Soils of many of the Ethiopian alpine areas are little studied. Menassie Gashaw and Masresha Fetene (1996) made soil analysis from the alpine and subafroalpine belt of the Bale Mountains, Senettie Plateau. As of the various studies soils of alpine ecosystems are of volcanic origin, and the composition of the bedrocks are lavas of various kinds, basalts, agglomerates, and tuffs, etc. The soils of upper alpine belts are comparatively porous with low water-holding capacity, but offering good drainage. The soil conditions in the lower part of the alpine belt are different, where the closed vegetation has facilitated accumulation and retention of more fine-textured material. The extent of humus accumulation is largely depending upon the degree of moisture available, and upon temperature conditions. The more plant cover and moisture content, the more humus is accumulated in the soil (Hedberg, 1964). Within the alpine belt the extent of humus accumulation appears to decrease with increasing altitude (i.e. decreasing temperature and decreasing growth rate of plants). This evidenced in one of the Ethiopian high mountains at Senettie plateau (Menassie Gashaw and Masresha Fetene, 1996). Monatane-Grassland Ecosytem 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 Dry Evergreen Montane Forest and Evergreen Scrub Ecosystem The Ethiopian highlands contribute to more than 50 % of the land area with Afromontane vegetation, of which dry montane forests form the largest part (Yalden, 1983; Tamrat Bekele, 1994). The evergreen scrubland vegetation occurs in the highlands of Ethiopia either as an intact scrub, i.e. in association with the dry evergreen montane forest or usually as secondary growth after deforestation of the dry evergreen montane forest. The Dry Evergreen Montane Forest and Evergreen Scrubland vegetations are the chjarachteristic vegetation types of this ecostem. These vegetation types were treated and discussed separately as follows: 3.1 Dry Evergreen Montane Forest 3.1.1 Description Typical dry evergreen montane forests in Ethiopia are situated on highlands and mountain chains with the following locations: the Chilimo forest (38° 10′ E and 9° 05′ N), 2400 ha; the Menagesha forest (38° 35′ E and 9° 00′ N), 2720 ha; and the Wof-Washa forest (39° 45′ E and 9° 35′ N), 3600 ha (Sebsebe Demissew, 1988; Tamrat Bekele 1994). Dry Evergreen Montane Forest is a very complex vegetation type occurring in an altitudinal range of 1500-2700 m, with average annual temperature and rainfall of 14-25° C and 700-1100 mm, respectively (Friis, 1992). It is inhabited by the majority of the Ethiopian population and represents a zone of sedentary cereal-based mixed agriculture for centuries. This type of forest develops in areas of relatively high humidity, but not much rain, and where there is a prolonged dry season. The forests have diminished due to human interference and replaced by bushlands in most areas. Soils have become shallow as a result of soil erosion that has been taking place for centuries (Zerihun Woldu 1999; Anonymous, 1992). The prominent features of tropical dry forests are their seasonality with respect to rainfall compared with the rain forests where the environment is stable throughout the year. Dry evergreen montane forests experience long dry seasons (4-8 months) and the rainy period is somewhat unreliable. During the dry season, not only moisture stress but also temperature increases and daytime humidity drops and watercourses either dry up or greatly diminish inflow (Demel Teketay, 1996). The bulk of the plateau consists of volcanic rocks. There are, however, Pre-Cambrian outcrops in the south (Sidamo zone), west (Wellega), north (Tigray) and east (Harar). The Pre-Cambrian rocks form heterogeneous substrata for plant growth. Some, like the ultrabasics of Wellega, are so deficient in nutrients, especially phosphorus that they tend to be very poor in vegetation cover. Extensive parts of the Tekeze Valley have impoverished vegetation cover because the substratum consists of fossil laterite soils, which are deficient in cations and have been exposed as a result of geological erosion (Zerihun Woldu, 1999; Anonymous, 1992) ). Montane Moist Forest Ecosystem 4.1 Description The montane moist forest ecosystem comprises high forests of the country mainly the southwest forests, which are the wettest, and also the humid forest on the southeastern plateau known as the Harenna forest. Several authors in the past (for example, Mooney, 1963; Chaffey, 1979; Mesfin Tadesse, 1986; Friis, 1986 and 1992; Lisanework Nigatu and Mesfin Tadesse, 1989; Uhlig, 1988; Zerihun Woldu et al., 1989; Kumlachew Yeshitila, 1997) studied the composition and structure of this forest vegetation and described them on floristic basis. The forest vegetation was stratified into four different layers, namely, upper canopy, sub-canopy, shrub layer and the ground layer. The upper canopy is occupied the spectacular emmergent trees of Pouteria adolfi-friederici. Afrocarpus falcatus become important in the mixed broad-leaved forests of the Bale Mountains, although conifers are generally less important in moist forests of Ethiopia. Other characteristic species in the canopy include Olea capensis subsp. welweitschii and subsp hochestetteri, Prunus africana, Albizia schimperiana, Milletia ferruginea and Celtis africana. Others such as Polyscias fulva, Schefflera volkensii, Trilepisium madagascariense, Schefflera abyssinica, Bersama abyssinica, Mimusops kummel are also associated to it. Sub-canopy species include Croton macrostachyus, Cordia africana, Dracena steudenri, Syzygium giuneense sub-sp. afromontanum, Sapium ellipticum, Ilex mitis, Erythrina brucei and Rothmannia urcelliformis. The shrub layer consists species of Coffee arabica, Galiniera saxifraga, Teclea nobilis, Ocotea kenyensis, Clausena anisata, Measa lnceolata and Maytenus spp. The Woody climbers are Ureara hypselodendron, Landolphia owarensis, Embelia schimperi and Jasminum spp. The ground vegetation are mainly herbaceous plants including Acanthus, Justicia, Piperoma, Galinsoga, Impatiens, Urtica and several grass species. In the attempt of classification of the vegetation types in montane moist forests of Ethiopia, Lisanework Nigatu and Mesfin Tadesse (1989) and Kumlacew Yeshitila (1997) recognised five and nine association groups at Harenna and Southwest forests, respectively. Plant community types recognised at Harenna forest have shown distinct variation in thier composition and structure of the vegetation across altitudinal changes, while those community types from Southwest forests were described mainly by their dominant species. The montane moist forest ecosystem is distiguished also by supporting luxuriant growing epiphytes Canarina, Orchids, Scadoxus and fern plants such as Platycerium and Drynaria. Mosses also occur in the wettest porton of forests associated to major branches and barks of trees. Generally in southwest plateau of Ethiopia, tertiary lava lie directly on the crystslline basement. The soils are predominantly developed on Trap series volcanics and metamorphic Precambrian basement materials. The color is red and red brown to silty loam (FAO, 1984). According to FAO/ UNESCO (1974) the soil in southwestern part of the country was clasified as Dystric Nitisols. Soil acidity tends to become an environmental problem due to leaching as a result of heavy rain that occur in the region. Acacia-Commiphora Woodland Ecosystem 5.1 Description The Acacia-Commiphora ecosystem is known for its varying soils, topography, and diverse biotic and ecological elements. These plant species are with either small deciduous leaves or leathery persistent ones. The density of trees varies from ‘high’, in which they form a closed canopy to scattered individuals to none at all forming open grasslands. The grasses do not exceed more than one meter, thus, no true savannah is formed. The altitudinal range in which the ecosystem is found is 900-1900 meters above sea level. The rainfall ranges from 600-1600 mm and the temperature varies from 18-27o C270c (100-800 mm, 210-27.50c for arid, 300-800 mm, 160c-270c for semi-arid, 700-1000 mm, 160c-280c for dry sub-humid respectively) (Ensermu Kelbessa et al., 1992). This is especially concerning the semi-arid moisture zone in which the ecosystem is found, where there are distinct differences in characteristics between the semi-arid plains, the semi-arid lakes and Rift Valley, and the semi-arid mountains and plateaus showing characteristic climatic variations. It is a dry ecosystem; at times, the dry season lasts as long as 10 months in a year. In moisture zone classification, the ecosystem extends from dry sub-humid to arid zones. Accordingly, a harsh and hot temperature with a low and uneven rainfall distribution generally characterizes the ecosystem. In such areas, evapotranspiration is very high due to the high temperature with strong occasional winds in the rainy season. This makes the monthly precipitation to exceed rainfall in some areas of the ecosystem (Engeda Mersha, 2000). Most of the areas in the ecosystem are defined as areas in which the ratio of annual precipitation to PET falls with in 0.05-0.065 ranges. 180c- Soil types vary depending on the locations and altitudes. For instance, the Southern and Central Hararge, the parts of the lowlands of Shewa and Wollo have predominantly vertisols and cambisols. On the other hand, eutric cambisols is common in Tigray. A soil types that is medium to shallow in depth, stony with low organic matter and deficient in nitrogen content. The Northern Rift Valley (starting from the footsteps of Northern Hararge highlands towards the north areas of lowland of Afar) is covered by shallow soils such as regosols, solonchaks and fluvistols. Such soils are usually affected by salinity (EPA, 1998). In the ecosystem, there is a substantive amount of water resources. There are seven major lakes located in the ecosystem, namely, Ziway, Langano, Abijata, Shalla, Awasa, Abijata and Chamo. These lakes are used for commercial fisheries, irrigation, recreation and for industrial purposes. In the lakes region of the ecosystem, most streams are perennial and the depth to ground water is 0- 150 m. A moderately large quantity of ground water is also a characteristic of some areas of this ecosystem. For instance, Southern parts of Oromia, Eastern parts of Afar and Northeastern Tigray are good examples. Most of the streams in these areas are intermittent and some are perennial. The ground water has a fair- to- poor chemical quality with a depth of 0 –270 m. Combretum-Terminalia Woodland Ecosystem 6.1 Description The geology of the Combretum-Terminalia ecosystem is characterized by extensive Late Tertiary that covers the pre-cambrian rocks that underlie all the other rocks in Ethiopia (Mohr, 1971). Old crystalline rocks overlay the pre-cambrian rocks in the relief down to Sudan (Mesfin Wolde Mariam, 1969), and valleys are largely composed of Phyllite with uncommon Chlorite Schist (Mohr, 1971). The topography/terrain is rugged; the upper limits about 1900 meters above sea level and the lower about 500 meters above sea level. The soil erosion rate is very high especially at the onset of rains. The soils are mainly Chromic and Pellic Vertisols, with Eutric Glysols and Eutric Histosols in areas that experience extreme seasonal flooding (FAO, 1984; EMA, 1988). This ecosystem generally occurs on rockier sandy soils (Beals, 1968; Tesfaye Awas et al., 2001). The climatic zones of Ethiopia are divided into three distinct zones (NAMSA, 2001), namely: dry climate, tropical rainy climate and temperate rainy climate. Among these, the tropical rainy climate occurs in the. A single maximum rainfall that runs from characterizes the rainfall in this region. The second highest mean maximum temperature for the country was recorded in the western lowlands of Ethiopia (35-40 oC) an area where the Combretum-Terminalia ecosystem occurs, next only to that of the Afar Depression (40 oC), an area where the Desert ecosystem type occurs (NMSA, 1996). The vegetation in this ecosystem has developed under the influence of fire. Thus, trees have very tick bark to cop with fire while most herbs have perennial bulbs (Menassie Gashaw, 2000), Lowland Tropical Forest Ecosystem 7.1 Description The Lowland Forest Ecosystem was first described by Chaffey (1979) as Lowland Forest that is comparable to the Moist Semi-deciduous Forest of Gana and Uganda and the Lowland Seasonal Rainforest of Malawi. He further stated that most of the species are classified as the Pan-Guineo-Congolian species. Friis (1992) described this vegetation as Dry Peripheral Semi-Deciduous Guino-Congolian Forest whereas Tesfaye Awas et al. (2001) described this ecosystem as Baphia abyssinica-Tapura fischeri Community in his study on vegetation of Gambella. This ecosystem is characterized by unimodal rainfall brought by tropical monsoon blowing from south Atlantic and Indian Ocean. It is also characterized by heavy rainfall during the wet season (May-October) and very little precipitation during the dry season (November-April). This forest occurs on well-drained sandy soils, with altitudinal range of 450 to 800 m, mean annual maximum temperature of 35 to 38° C, mean annual minimum temperature of 18 to 20° C, mean annual temperature of 28 to 30° C and annual rainfall range of 1300-1800 mm (Friis, 1992, Demel Teketay, 1999). The eastern part of the forest extends on the Precambrian basement, which is exposed at the edge of the plateau. Elsewhere the forest is situated on Pleistocene-Holocene deposits, which overlie the older rocks (Zerihun Wouldu, 1999). Desert and Semi-Desert Scrubland Ecosystem 8.1 Description It is a very dry zone vulnerable to wind and water erosion even with little or no pressure on the vegetation from grazing. The vegetation consists of deciduous shrubs, dominated by Acacia sp. interspersed with less frequent evergreen shrubs and succulents. It has very variable grass vegetation. The people of the area are pastoral and agro-pastoral. Large scale irrigated agriculture is gaining importance in some areas of the ecosystem. This ecosystem is the extreme lowland region of the country. The flora has developed an advanced xeromorphic adaptation. Shrubs and trees have developed dwarf growth and have small, sclerenchymatic or pubescent leaves. They have an adapted resistance to browsing through thorns and development of alkaloid content. The vegetation is very scattered above the ground with extremely well developed deep root systems. The topsoil is very often highly salty, thus the development of salt tolerance. The region is very low with erratic rainfall. The south and southeastern part of the ecosystem have two rainy seasons while the north and the Northeast have one (Zerihun Woldu, 1999; Demel Teketay, 1999). Harsh and hot temperature is the characteristic of the ecosystem with low and uneven distribution of rainfall. High evapotranspiration is another phenomena in the ecosystem, which causes excess monthly PET than rainfall. Concerning the moisture zone, the ecosystem extends from semi-arid to hyper-arid. Accordingly, a great variation is observed in different climatic aspects of the ecosystem. Based on the temperature and moisture regime, the desert and semi-desert ecosystem can be explained by the context of arid (pastoral), semi-arid (pastoral/cultivation) and hyper-arid (EPA, 1998). This ecosystem has mean annual rainfall of between 300-800 mm, a mean annual evapotranspiration of 1600-2100 mm and mean annual temperature of 16-27o C. The parts of the ecosystem that fall under the arid zone are characterized by mean annual rainfall of between 100-800 mm, mean annual temperature of 21-27.5o C and mean annual precipitation between 1700-2600 mm (Engeda Mersha, 2000). Tertiary and quaternary volcanic are included in the parent materials. Colluviums from highland plateau, Aeolian deposits as well as marine deposit are also good characterstics. In general, sol types in the ecosystem vary depending on location and altitude. Vertisoles, Cambisoles, Calcisols, Gypsysols, Lithosoles, Regosoles, Solonchks and fluvistols can all be found in the ecosystem. Varied water resource regimes are found in the ecosystem. The areas covering most of the drier lowland parts of the ecosystem situated in the southern parts of Oromia (Moyale area), the eastern most parts of Afar and some parts in the north-eastern Tigray are characterised by localized and moderately large quantities of ground water, especially along valleys. They have mostly intermittent streams with some perennials. The quality is fair-to-poor. The depth of the ground water is 0-270 m. Those areas covering the southeastern parts (the Ogaden) are characterized by localized and limited quantity of ground water with a depth of 0-300 m. The quality is fair-to-poor chemically. Wetland Ecosystem 9.1 Description Ethiopia possesses a great diversity of wetland ecosystem (swamps, marshes, flood plains, natural or artificial ponds, high mountains lake and micro-dams) as a result of formation of diverse landscape subjected to various tectonic movements, a continuous process of erosion, and human activities. The different geological formation and climatic conditions have endowed Ethiopia with a vast water resources and wetland ecosystem including 12 river basins, 8 major lakes and many swamps, floodplains, and man made reservoirs with a total annual surface runoff about 110 billion cubic meter (EFAP, 1989). According to Hillman (1993), there are 77 wetlands in Ethiopia and Eritrea with a total coverage of 13,699 km2 or 1.14% of the total landmasses of the country The Ramsar Convention (Article 1.1) defined wetlands as: “areas of marsh, fen, peat land, or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide doesn’t exceed six meters”. In addition, the convention (Article 2.1) provides that wetlands: “may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six meters at low tide lying within the wetlands. In the Ethiopian context marshy areas, swamp lands, flood plains, natural and artificial ponds, volcanic crater lakes, high mountain lakes and upland bogs are treated collectively as wetland ecosystems. This booklet, therefore, deals on swamps, marshes, floodplains, ponds, micro dams, high mountains as well as crater lakes and upland bogs whose formation has been dominated by water and whose processes and characteristics are largely controlled by water. Wetland ecosystem has been considered as wasteland that have little or no value at all, and converted to agriculture and grazing through drainage. Often, they are considered as breeding sites and sources for several water borne diseases both to human and domestic animals. Defining the various habitat types in wetland ecosystem Flood plains can be defined as land adjacent to an active river channel which are occasionally flooded by those bodies of water and remain dry for varying portion of the growing season (Mitch & Gosselink, 1993). According to FAO (1984), swamps are defined as wetlands dominated by trees or shrubs, and marshes as wetlands dominated by emergent herbaceous vegetation. Swamp (marshy) ecosystem is an area, which is frequently or continually flooded, usually with emergent vegetation adapted to saturated soil condition. These areas are often with high water table and sub-surface water within the root zone. In most cases, flood plains are conspicuous features of the landscape in contrast with the surrounding vegetation. As a result, this habitat attracts wildlife, which seek the refuge of the diversified habitat types. Wetland ecosystem is considered to be more productive than the adjacent area because of the periodic inflow of nutrients. There is a considerable diversity of swamp and marshy habitats in Ethiopia and for the purpose of this booklet we used both terms interchangeably. Floodplain differs from swamps in that it arises as a result of seasonal submergence by spill over from rivers, lakes or other water bodies. Swamp and flood plain generally occur where the water table is at or near the surface of the land or where the land is covered by shallow water depth. Strictly speaking, defining Wetland ecosystem in the Ethiopian context seems uneasy because of considerable change in hydrological properties (seasonal and long-term) and vegetation composition overtime and absence of clear boundaries between the wetlands and adjacent aquatic as well as terrestrial lands. The very transient nature they have with a great array of their types defied a clear distinction of what wetland ecosystem is. Characteristics of wetland ecosystem In wetland ecosystem water is the primary factor controlling both the plant and animal life. It favours particular type oftrees, shrubby species and associated herbs and grasses. Typical characteristic species of wetland ecosystem include those of aquatic macrophytes such as Cyperus, Eleocharis, Scirpus, Echinochloa, Panicum, Alisma plantago-aquatica, Nymphaea, Typha, Paspalidium, Potamogoton, Wolffia, Aeschynomene, Phragmites, Urochloa, Veronica, Hydrocotyle, Polygonium, kyllinga etc., and tree species include Ficus sychomorus, Tamarindus indica, Celtis africana, Mimusops kummel, Syzygium guineense, Terminalia brownii, Acacia polyacantha, Kigelia abyssinica, Phoenix sp., Trichilia sp., Diospyros sp. Although swamps, marshes, and flood plains are known to be a home to many different kinds of birds, mammals much more remains unsurveyed specific to the habitat types. Some birds, for example, Spot-breasted Plover, Blue-winged Goose, Rouget’s Rail, White-winged Flufftail, Wattled Crane, Corn Crake, Shoebill, Black-winged Pratincole, Great Snipe, and Lessr Flamingo in general favour, feed or breeds in wetlands (Mengistu Wondafrash, 2000). The resource base Swamp and Marsh are terms used to describe range of habitat types affected by water. These two habitat types hereafter refereed as swamp ecosystem, covering an estimate area of 1803 km2, which is about 0.16% landmasses of the country. In wetter part of the country, for example, in Illubabor swamplands are most common that accounts up to 5% of the area in the highlands. Similarly, other highlands of the Western, South, and Southwest of the country including Jimma, Wollega and Illubabaor Zones of Oromia Region, Keff-Sheka of South Region as well as the low-lying regions of Ethiopia have considerable area of wetlands (swamps and flood plains). Aquatic Ecosystem 10.1 Description Aquatic in literal meaning refers to water. As an ecosystem, widely taken, it includes freshwater (rivers, reservoirs and lakes), marine (oceans and seas) and estuarine (coastal, bays, tidal) ecosystems. The Ethiopian aquatic ecosystem has high diversity areas such as major rivers and lakes that are of great national and international importance. The country is well known for its richness in water potential. There are about 30 major lakes that are located in different ecological zones. These lakes are situated at altitudes ranging from about 150 m below sea level high up to 4000 m. The surface area of the lakes vary considerably from less than 1 km² to over 3600 km² and mean depths range from few meters to over 260 meters. However, the major lakes that are of economic importance are concentrated in the Rift Valley.
Posted on: Thu, 25 Dec 2014 06:06:35 +0000