Some browse plants of Ethiopia**

H.N. Le Houérou And M. Corra

International Livestock Centre for Africa, Addis Ababa

1. General remarks

2. Introduction

3. The plant formations

3.1 Evergreen open woodland with Juniperus procera

3.2 Mixed evergreen and deciduous open woodland

3.3 Mesophyllic deciduous open woodland

3.4 Open woodland with Acacia etbaica

3.5 Open woodland with Acacia asak

3.6 Open woodland with Acacia bussei

3.7 Frutescent formations with Acacia bussei

3.8 Frutescent formations with Acacia senegal and Commiphora spp.

3.9 Frutescent formations with Acacia mellifera

3.10 Frutescent formations with Acacia nubica

3.11 Frutescent formations with Acacia oliveri and Acacia ehrenbergiana

3.12 Medium height grassland with Chrysopogon plumulosus and Andropogon greenwayii

3.13 Medium height grassland with Chrysopogon plumulosus

3.14 Low grassland with Cynodon dactylon and Cynodon nlemfluensis

4. Browse plants

5. Browse plants: research and experimentation

6. Conclusion

1. General remarks

Ethiopia, with natural grazing land estimated to amount to 69 million hectares (excluding fallows), is the country with the largest number of livestock in Africa (approximately 30 million cattle) (see Table 2). Traditionally, 5 major bioclimatic zones are identified according to altitude, climate and the production system of the population.

Table 1. Main ecological zones of Ethiopia

Table 2. Number of livestock in Ethiopia (1950–1976) in 10³

Species	1950	1974	1975	1976	Variation (%)
Cattle	18 900	26 926	25 879	25 963	+ 37.4
Sheep	9 559	23 459	23 978	23 065	+141.3
Goats	9 692	17 646	17 232	17 064	+ 76.1
Horses	5 213	6 735	6 750	6 780	+ 30.0
Camels	855	970	950	960	+ 12.3
Total	44 219	75 736	70 979	70 912	+ 60.4

While the fertile and overpopulated highlands are occupied by sedentary crop and livestock producers, the lowlands, which are often unsuitable for crop production, are sparsely populated by nomadic or semi-nomadic herdsmen. Altitude varies from –200 m to +4600m and is the determining factor in the distribution of the various plant formations and the flora of which they consist.

2. Introduction

The natural grazings of Ethiopia did not escape the drought of 1971–74 which also struck the countries of the Sahel. The result has been to produce a real disequilibrium in the agropastoral ecosystems. A high percentage of livestock was lost and the natural grazings became more or less severely degraded. The current need is for systematic reafforestation of both the highlands and the lowlands, as well as improved management of grazing.

This need forces us to give more detailed consideration to browse plants, since these species, in addition to their sizeable contribution to animal feeds, not only protect and improve the soil, but also provide fuel and supply the raw material for family utensils, building huts, and for medicines.

In the present study we have briefly described the plant formations which make up the extensive rangelands of Jijiga and northeast Ethiopia, for which the most important browse species are given. Table 3 shows observations relating to 82 browse species. Finally we have put forward suggestions for the introduction or extension of browse species in order to improve rangeland, both in the subhumid, the arid and semiarid zones.

Table 3. Some browse plants of Ethiopia

Captions to table 3
First column
The species are listed in alphabetical order, with the family to which they belong in brackets.

Second column
The limits in altitude at which each species is found in the surveyed areas, although no claim is made to show the altitude limits for the country as a whole.

Third column
Various plant formations as described in the text (chapter 3):

1. Evergreen open woodland with Juniperus procera
2. Mixed evergreen and deciduous open woodland
3. Mesophyllic decidous open woodland
4. Open woodland with Acacia etbaica
5. Open woodland with Acacia asak
6. Open woodland with Acacia bussei
7. Frutescent formations with Acacia bussei
8. Frutescent formations with Acacia sénégal and Commiphora spp.
9. Frutescent formations with Acacia mellifera
10. Frutescent formations with Acacia nubica
11. Frutescent formations with Acacia oliveri and Acacia ehrenbergiana
12. Medium height grassland with Chrysopogon plumulosus and Andropogon greenwayii
13. Medium height grassland with Crysopogon plumulosus
14. Low grassland with Cynodon dactylon and Cynodon nlemfluensis

Fourth column
Bioclimatic zones

a) D = Desert P < 100 mm
b) The arid zone: 100 < P < 400 mm
     LA = lower arid: 100 < P < 200 mm
     MA = medium arid: 200 < P < 300 mm
     UA = upper arid: 300 < P < 400 mm
c) Semi-arid zone: 400 < P < 600 mm
     LSA = Lower semi-arid: 400 < P < 500 mm
     USA = Upper semi-arid: 500 < P < 600 rnm
d) Subhumid zone: 600 < P < 800 mm
     LSH = lower subhumid: 600 < P < 700 mm
     USH = upper subhumid: 700 < P < 800 mm
e) Humid zone: 800 < P < 1200 mm
    LH = lower humid: 800 < < 1000 mm
    UH = upper humid: 1000 < P < 1200 mm
f) Hyper-humid zone
    HH with P > 1200 mm

Fifth column
Palatability
1. Highly palatable = HP
2. Palatable = P
3. Less palatable = LP
4. Unpalatable = UP
5. Toxic TO

Sixth column
Parts consumed
L = leaf
FR = fruit
YB = Young branches
B = Bark

Seventh column
Animal species
CAT = cattle
SH = sheep
GO = goats
CAM = camels

It should be noted that in Ethiopia much remains to be done as regards browse plants, not only in terms of research and experimentation but also in connection with the introduction of new species, their propagation and their utilization by livestock.

3. The plant formations

The plant formations described make up the extensive rangelands of south-eastern Ethiopia, and particularly the north of the Ogaden in the Jijiga area, and also the rangelands of the northeastern region, northeast of Dessie in the Afar country (Danakil Desert).

The Jijiga rangelands, which lie between 7°52'–9°55' latitude North and 12°05' – 44°25' longitude East, form part of the vast Harar-Ogaden plateau east of the Ethiopian Rift Valley. They cover 35,000 km². The higher part of the plateau (> 1500 m) is inhabited by the Oromo or Galla people, who are sedentary mixed farmers, while the lowlands (> 1500 m) are the domain of the Somali nomads, semi-nomads, or trans-humants peoples.

The northeastern rangelands are found between 11°00'–12° 15' latitude north and 40°00'–41°00' longitude east, in the province of Wollo. They cover 75,000 km², of which 12,000 km² constitute the zone studied here. The Oromo sedentary mixed farmers live in the highlands and the Afar nomads inhabit the lowlands.

Passing from high altitude to low altitude, the following different plant formations are noted:

3.1 Evergreen open woodland with Juniperus procera

This multi-strata formation is found at altitudes between 2000 and 2200 m, in the upper subhumid zone, on limestone hardpan. Rainfall varies between 800 and 1200 mm.

The characteristic tree and shrub species are: Juniperus procera, Olea chrysophylla, Sideroxylon oxyacantha, Ficus thonningii, Acacia negrii, Entada abyssinica, Myrsine africana, Dombeya burgessiae, Dodonea viscosa, Euclea schimperi, Carissa edulis, Premna schimperi, Heteromorpha trifoliata, Colutea istria, Pterolobium stellatum, Calpurnia aurea, Acacia abyssinica, A. negrii, Barbeya oleoides.

The grassland is dominated by a number of Graminae:
Hyparrhenia pseudocymbaria, H. hirta, H. dregeana, H. rufa. As well as other species, such as: Andropogon greenwayii, Chloris pycnothrix, Crotalaria spinosa, Rhynchosia erythreae, Exotheca abyssinica, Tephorosia interrupta, Gnidia somalensis.

3.2 Mixed evergreen and deciduous open woodland

This formation, which has several ill-defined strata, differs from the previous one owing to the absence of Juniperus procera and a few other species such as Dombeya burgessiae, Acacia negrii, Ficus thonningii, as well as the presence of Acacia seyal var. seyal, Acacia etbaica and Acacia nilotica subsp. kraussiana on soils derived from limestone.

The characteristic species are: Olea chrysophylla, Carissa edulis, Dodonea viscosa, Euclea schimperi, Osyris abyssinica, Acacia etbaica, Acacia seyal var. seyal, Acacia nilotica subsp. kraussiana, Cussonia holstii, Pistaela falcata.
We also noted: Enneapogon schimperianus, Heteropogon contortus, Aristida adscensionis, Blepharis procera, Cadia purpurea, Hyparrhenia hirta.

Mixed evergreen and deciduous open woodlands are frequently found in the lower subhumid zone, at altitudes between 1700 and 2000 m on rendzina, limestone hardpan and soils derived from basalt.

3.3 Mesophyllic deciduous open woodland

This is a multi-strata formation primarily consisting of tree and shrub species with large deciduous leaves. Frequently it covers soils which have undergone little evolution and consists of granite, gneiss and schist, lying between 1500 and 1900m, both in the lower subhumid and the upper semi-arid zones.

The following are found: Combretum molle, Terminalia brownii, Dichrostachys cinerea, Acacia brevispica, Rhus natalensis, Ozorea insignis, Sterculia rhyncocarpa, Ormocarpum Trachycarpum, Canthium bogoensis, Canthium setiflorum, Grewia schweinfurthii, Grewia tenax, Croton dichogamus, Pappea capensis, Carissa schimperi.

The grass stratum, which has a very low cover and is very little developed, consists of: Heteropogon contortus, Chrysopogon plumulosus, Aristida adscensionis, Harpachne schimperi, Enneapogon desvauxii.

3.4 Open woodland with Acacia etbaica

This plant formation covers small areas of the Jijiga rangelands at 1500–1800 m, and is thus found in the upper semi-arid zone, which is often seriously degraded. Open woodland with Acacia etbaica, is strictly speaking a multi-strata formation which was found both on the Jijiga plain on various limestone soils (with crusts) and on vertisols on the Togo-Wouchale plain.

It consists of shrub and tree species as follows: Acacia etbaica, Acacia nilotica subsp. kraussiana, Balanites glabra, Commiphora africana, Euphorbia grandis, Acacia seyal var. seyal Ziziphus mauritiana, Barleria hildebrandtii, Acacia senegal, Grewia villosa;
and other species such as: Andropogon greenwayii, Chrysopogon plumulosus, Cenchrus ciliaris, Aristida adscensionis, Gomphocarpus fruticosus, Flaveria australasica, Solanum incanum, Kalanchoë marmorata.

The plant formation covering the major part of the Jijiga plains is medium-height grassland with Chrysopogon plumulosus and Andropogon greenwayii. This formation results from the degradation of open woodland with Acacia etbaica, under the combined influence of man (crops, wood and charcoal), his animals and severe runoff erosion, producing a patchy cover of vegetation arcs with A. greenwayii. The medium height grassland with Chrysopogon plumnlosus and A. Greenwayii consists of 2 distinct bands often separated by patches of bare soil 5 to 10 m across. The first unit consists of the combination of Chrysopogon plumulosus and Andropogon greenwayii, which covers the soil thoroughly, while the second one is largely dominated by Eragrostis barrelerii and has a negligible soil cover.

In this medium-height grassland the following shrubs are found, at very infrequent intervals: Acacia etbaica, Acacia nilotica subsp. kraussiana, Balanites glabra, Zizphus mauritiana, Ziziphus mucronata, Acacia tortilis subsp. spirocarpa. These shrubs, which are browsed substantially in this formation, are rarely over 50 cm high.

Cultivated and fallow land contain the following species: Tagetes minuta, Leucas martinicensis, Solanum nigrum, Crotalaria spinosa, Cynodon dactylon, Brucastrum arabicum.

3.5 Open woodland with Acacia asak

This formation covers a fairly wide area of extensive rangeland in northeastern Ethiopia, and is found in the lower semiarid zone, on volcanic outcrops and coarse soils.

The main species in this formation are: Acacia asak, Acacia etbaica, Berchemia discolor, Dobera glabra, Boscia angustifolia, Cadaba rotundifolia, Boscia coriacea, Acacia mellifera, Capparis decidua, Acacia senegal.

Shrubs and grasses are also found: Vernonia cineranescens, Grewia bicolor, Grewia tenax, Dicrostachys cinerea, Svensonia laeta, Abutilon fruticosum, Chrysopogon plumulosus, Enteropogon rupestris, Chlorfs roxburgiana, Aristida adscensionis, Dichanthium radicans, Tetrapogon cenchrifomis.

3.6 Open woodland with Acacia bussei

This formation is extensively present in the Shebelle valley, on red sandy loam soils with a varying limestone content, in the lower semi-arid zone. It is highly degraded. It should be noted that large numbers of dead Acacia bussei were frequently seen covering large areas, caused by the considerable surface sealing of the soil.

Associated with Acacia bussei are found the following ligneous species: Acacia nubica, Acacia senegal, Acacia brevispica, Balanites glabra, Dicrostachs cinerea, Grewia villosa, Acacia tortilis, subsp. spirocarpa, Acacia seyal var. seyal. Tragus racemosus is the commonest grass and is abundant in places.

Also found are: Chlorls pycnothrix, Tragus berteronianus, Enneapogon desvauxii, Hibiscus calyphyllus, Leucas martinicensis, Tagetes minuta.

At the lower altitudes Acacia bussei is often associated with Andropogon kelleri. This other formation, found in the upper arid zone on limestone hardpan with brown-red sandy loam or loamy sand soils, consists of the following species: Boscia minimifolia, Acacia horrida,subs. benadirensis, Acacia edgworthii, Balanites glabra. And grasses such as: Stipagrostis uniplumis, Leptothrium senegalensis, Entoropogon rupestris.

Fruit-bearing shrubs, found equally in the extensive rangelands of Jijiga and of northeastern Ethiopia, are found in formations consisting primarily of ligneous phanerophytes, the height of which lies between 1 and 6 m. These bushy formations cover rocky outcrops, coarse soils and deep clays with a sandy alluvial content. Often the favourite haunt of goats and camels, these formations frequently consist of impenetrable thickets.

The distribution of these formations as a function of altitude, which varies between 1200 and 600 m, and the most abundant species, usually an Acacia, allowed us to identify the following subtypes:

3.7 Frutescent formations with Acacia bussei

This is a bushy formation found on gneiss outcrops on the extensive Jijiga rangelands at altitudes between 1600 and 1400 m, in the upper semi-arid zone. With Acacia bussei are found: Acacia senegal, Acacia brevispica, Acacia nubica, Balanites glabra, Dichrostachys cinerea, Grewia schweinfurthii, Ziziphus mucronata, Commiphora africana, Grewia villosa. And other species such as: Cenchrus ciliaris, Eragrostis papposa, Aristida adscensionis, Brochloa panicoides, Tragus racemosus, Tagetes minuta, Pegoletta senegalensis, Achyranthes aspera, Cassia italica, Lycium shawii.

3.8 Frutescent formations with Acacia senegal and Commiphora spp.

This is a bushy formation with a shrub stratum dominated by Acacia senegal. It is often found on soils with good drainage between 1200 and 900 m, in both the lower semi-arid and upper arid zones.

The following tree species were identified, often far apart and few in number: Dobera glabra, Acacia tortilis subsp. spirocarpa, Boscia coriacea, Demonix elata, Balanites glabra, Balanites aegyptiaca, Balanites orbicularis, Boscia angustifolia.

These species are associated with: Acacia senegal Vernonia cinerascens, Sericocomopsis pallida, Commiphora sp., Grewia erythreae, Acacia nubica, Grewia villosa.

The sparse grass stratum consist of: Chrysopogou plumulosus Dactyloctenium, scindicum, Tetrapogon cenchriformis, Tetrapogon tenellus, Seddera latifolia, Abutilon fruticosum, Tribulus terrestris, Cassia italica, Aerva javanica.

3.9 Frutescent formations with Acacia mellifera

This is a bushy formation found on coarse soils, but also on deep soils subject to seasonal flooding between 1050 and 900 m in the upper arid zone. It consists of many species common to the Acacia senegal frutescent formation. The grass cover is more dense on black, deep soils subject to seasonal flooding:

The characteristic species are the following: Acacia mellifera, Dichrostachys cinerea, Grewia bicolor, Dobera glabra, Boscia coriacea, Cordia sinensis.

Association with Chrysopogon plumulosus, Lintonia nutans is often found; other species are also found such as: Enteropogon rupestris, Coelachyrum poseflorum, Aristida adscensionis, Pavonia arabica, Puppalia lappacea, Satanocrater somalensis.

3.10 Frutescent formations with Acacia nubica

This a formation with a physiognomy identical to the two formations described above, is which many of the species are the same. It is found in the upper arid between 1000 and 900 m, on seasonally floooded deep soils with a sandy content. It may be noted that according to the herdsmen Acacia nubica is the species which has expanded most rapidly since the 1973 drought. Although sought after by goats and camels this species is highly aggressive and now covers a large area, to the detriment of grassy formations with Chrysopogon plumuosus.

3.11 Frutescent formations with Acacia oliveri and Acacia ehrenbergiana

This bushy formation is usually found between 700 and 600 m on rocky outcrops. It covers a small area in the project zone of the northeastern rangelands, in the middle arid zone. The characteristic species are:

Acacia ehrenbergiana, Acacia oliveri, Acacia tortilis subsp. tortilis, Commiphora sp., Boscica coriacea, Cabada rotundifolia Cabada glandulosa, Grewia tenax.

The grass cover is dominated by:

Chrysopogon plumulosus, Ischaemum afrum Jatropha lobata, Seddera latifolia Aerva javanica Senra incana.

3.12 Medium height grassland with Chrysopogon plumulosus and Andropogon greenwayii

This is a grassy formation covering a large area of the Jijiga plains, at altitudes between 1500 and 1800 m, in the upper semi-arid zone. The medium height grassland has two distinct units, of alternatively dense and light plant cover (vegetation arcs) and bare soil, each strip being 5 to 10 m across. Some ligneous species, few and far between and with a height of not over 50 cm, are occasionally present.
The following were identified:
Acacia etbaica, Acacia nilotica subsp. kraussiana, Acacia tortilis subsp. spirocarpa Ziziphus mauritania Ziziphus mucronata Balanites glabra.

The densely covered strips are dominated by Andropogon greenwayii and/or Chrysopogon plumulosus, the almost bare strips are dominated by the small annual Eragrostis barrelieri.

3.13 Medium height grassland with Chrysopogon plumulosus

The vast plains which extend over the central and northern part of the northeast rangelands, which have heavy and deep soils which are seasonally damp to flooded, have grass formations which possess considerable potential for animal production.

The most abundant grass, always present in these grassy formations, is Chrysopogon plumulosus. This perennial grass, with a height often reaching 80 cm when flowering occurs, is often associated with Lintonia nutans and Ischaemum afrum.

Associated with species are found: Cordia sinesis, Rhynchosia malacophylla, Indigofera schimperi, Dichanthium radicans, Sporobolus ioclados, Cenchrus ciliaris, Asystasia schimperi, Ruellia patula, Jatropha lobata, Aristida adscensionis, Tetrapogon cenchriformis, Panicum coloratum.

On the edges of bare patches are found: Abutilon figarianum, Tribulus terrestris, Pavonia sp., Aerva javanica.

3.14 Low grassland with Cynodon dactylon and Cynodon nlemfluensis

This formation covers a fairly wide area of vertisols subject to seasonal flooding in the Fafan valley of the Jijiga rangelands. The forage production of this formation is estimated at 5000–6000 kg DM/ha/year.

Together with Cynodon dactylon and Cynodon nlemfluensis the following species were identified: Elusine floccifolia, Eriochloa nubica, Cyperus alopecuroides, Panicum coloratum, Cyperus dives, Hibiscus cannabinus.

4. Browse plants

In this part of the report we have compiled a table showing the species identified and the observations made in the field with regard to the ligneous plants which serve as browse to a greater or lesser degree.

5. Browse plants: research and experimentation

In any rangeland improvement programme using browse plants, research must be carried out on indigenous species and the introduction and multiplication of known species must be planned.

During the ecological studies carried out on the Jijiga range lands research was undertaken on the following species together with about fifty others: Atriplex nummularia, Atriplex halimus, Atriplex canescens, Acacia cyanophylla, Opuntia ficus indica var. inermis.

The experiments were carried out on 2 ha at the experimental station belonging to the Ministry of Agriculture at Lemma Defa, 7 km east of Jijiga. Although definitive results were not obtained owing to the Somali-Ethiopian war, in 1977/78, Atriplex, Acacia cyanophylla, and Opuntia ficus indica var. inermis, gave highly encouraging initial results and might easily be used for improving rangeland in the Jijiga plain, at 1500 m altitude with a rainfall of 500 mm.

As regards the indigenous species of the Jijiga and northeastern rangelands, research on their physiology, establishment and management should be carried out for the following ligneous varieties: Leguminosae: Acacia etbaica, Acacia edgworthii, Acacia tortilis subsp. spirocarpa, Acacia nilotica subsp. kraussiana, Ormocarpum trachycarpum, Colutea istria.
Rubiaceae: Canthium bogoensis, Centhium setiflorum and Canthium schimperianum
Capparaceae: Boscia minimifolia, Cadaba farinosa
Salvadoraceae: Dobera glabra, Salvadora persica
Convolvulaceae: Seddera bagashawei, Seddera latifolia
Compositae: Veronica cinerascens

6. Conclusion

In Ethiopia as in the Sahel countries which suffered the 1971–74 drought, it now appears necessary to improve the rangeland through better management of browse plants. In any rangeland improvement programme using browse plants the necessary steps are to research indigenous species, and introduce and multiply those best adapted and known for their multiple utilization.

The following species seem worthy of interest in Ethiopia:

1.Faidherbia albida, and Acacia tortilis subsp. spirocarpa found in agropastoral systems of the Rift Valley above 1200 m and 500 mm rainfall.
2.Opuntia frcus indica var. inermis, associated with those species of Atriplex and phyllodinious Acacia, and other species of the Mediterranean and subtropical zone, for altitudes varying from 100 to 2800 m.
3.For the subhumid and semi-arid highlands, anti-erosion hedges could be grown between cultivated fields, using species such as Morus alba, Coronilla glauca and Medicago arborea.
4.For the humid zones of western Ethiopia Leucaena leucocephala has been successfully introduced (Taylor, 1980).
5.For the driest areas above 1200 m: Prosopsis juliflora and Parkinsonia aculeta.