Previous PageTable Of ContentsNext Page

VI. Establishment, utilization and management

The role of browse in the management of natural grazing lands*1

H.N. Le Houérou

1 Presented upon invitation as position paper, item no. 10,8 the world Forest Congress, Jakarta, Indonesia 16–28 Oct. 1978. Original: English.


1. Introduction

2. Importance of fodder shrubs and trees in various ecological zones

2.1 The Mediterranean basin

2.2 The dry tropics of sub-Saharan Africa

2.3 In northern America

2.4 In Latin America

2.5 In Australia

2.6 Selection of browse by herbivores

2.7 Management of browse ecosystems

3. Plantation of fodder shrubs and trees as fodder reserves

3.1 Spineless cacti

3.2. Saltbushes (Atriplex sp. pl.)

3.3 Acacia

3.4 Leucaena

3.5 Mesquites (Prosopis spp.)

3.6 The honey locust, Gleiditschia triacanthos

3.7 Carob

3.8 Other legume species

3.9 Olive

3.10 Calligonum

3.11 Saxaouls

3.12 Salsola

3.13 Sagebrush

3.14 Mulberry

3.15 Establishment and management techniques

3.16 Cost of establishment and management

3.17 Use of fodder shrubs and trees for reclamation of marginal land

6. Conclusions

References


1. Introduction

Natural grazing lands occupy some 30 million km2 (3 billion ha) (FAO Production Yearbooks) i.e. 22% of the world's land surface, whereas forest and woodland represent 40 million km2, almost 30% of the surface of the earth. Probably over 50% of the forests and woodlands are also, to a greater or lesser extent, used by livestock and wild herbivores, so that at least one third of the world's land surface may be considered as natural grazing grounds.

The role of browse in natural grazing lands varies in importance according to ecological zones. Under temperate climates and in the humid tropics, browse is of limited use in animal production; however in the Mediterranean isoclimatic zone, the arid and semi-arid tropics and in montane areas, browse plays an essential role in animal production and thus greatly contributes to the protein supply of mankind.

In Africa, for instance, over 250 million head of domestic animals live in arid, semi-arid and montane zones, where browse is an important qualitative component in livestock diets, as we shall see further on.

It has been estimated that, in the Mediterranean basin, over 50% of the total income from forest and woodland maybe ascribed to animal production. Browse is also very important in large tracts of rangeland in North and Latin America and huge areas in Australia (top feed). The importance of browse was recognized early in history through what the Roman agronomists used to call their "aerial pastures".

However, not all ligneous species are useful as livestock feed and many are considered as pests, particularly in the tropical savanna is, where competition from woody species, reduces the production of grasslands. Various techniques of bush clearance have been developed in order to control the encroachment of undesirable woody species on grassland.

The present paper is not concerned with the latter aspect, but rather with those woody species which are considered desirable for livestock production and which are generally known as browse.

2. Importance of fodder shrubs and trees in various ecological zones

2.1 The Mediterranean basin

In the Mediterranean basin browsed vegetation i.e. depleted forests, garrigue, matorral and maquis, cover some 60 million ha and contribute substantially to the feeding of some 30 million head of cattle, 60 million sheep and 30 million goats.

The woody steppes of North Africa and the Near East cover huge areas, in the order of 120 million ha, from which 5 million head of cattle, 60 million sheep, 30 million goats and 2.2 million camels derive their subsistence.

This livestock population is the basic source of protein (meat and milk) for over 180 million people in North Africa and the Near East, although imports of animal products in this region are also significant, especially in oil-rich countries.

In the non-arid Mediterranean zone the main browse species are shrubs and trees, such as oaks (Quercus ilex, Q. suber, Q. coccifera, Q. calliprinos) olives (Olivus europea), Carob (Ceratania siliqua, Phillyrea, Erica, Cytisus, Pistacia, Arbutus) and many others. In the arid steppes many dwarf shrubs constitute the bulk of animal feed, such as Artemisia herba alba, Calligonum, Echiochilon, Helianthemum, Atriplex, Gymnocarpos, Argyrolobium, etc.

Productivity of browse in the humid and sub-humid zones is of the order of 1000 kg DM/ha per year, i. e. a carrying capacity of 1 sheep or 1.2 goat per ha/year (Long et al, 1967). In the semi-arid zone, productivity is of about half that figure and the carrying capacity is equivalent to 25 kg on the hoof and 30 kg of milk per ha (Liacos and Mouloupoulos,1967). In many cases productivity could be considerably increased (two to five fold) through various techniques (Long et al, ibid, Liacos and Mouloupoulos, ibid, Etienne, 1976, Papanastasis, 1977). The feed value of browse is low to intermediate in terms of energy (30 to 55% of digestible organic matter or 0.25 to 0.40 Scandinavian feed units per kg of DM) but usually high in DP (10 to 20% in the DM content) according to Sarson and Salmon (1978).

In the arid Mediterranean woody steppe, net primary consumable production is about 300–600 kg of DM/ha per year (Le Houérou and Hoste, 1977). Similarity, the energy value of browse is rather low, 0.3 to 0.4 FU per kg of DM but, again, this feed is rather high in DP, at 4 to 20% in the DM (Sarson and Hamrouni, 1974).

Compared to cultivated fodder crops and artificial pastures, such productivity per unit area may seem mediocre; however, given the enormous areas concerned, the contribution of browse to animal production is extremely important especially with regard to the protein component of livestock diets.

2.2 The dry tropics of sub-Saharan Africa

In the savannas in the arid, semi-arid sub-humid zones, ligneous species are an important component. Many of them are browsed or lopped as dry-season feed. Ligneous species also have an important effect on the quality, seasonality and productivity of the grass cover growing beneath their shade.

Some species, such as Acacia albida, play a determining role in agro-pastoral ecosystems, not only through their feed value but also in the maintenance of soil fertility in these systems (Charreau and Vidal, 1965; Giffard, 1972; Wickens, 1969). The main browse species found are the following:
Acacia: A. albida, A. Senegal, A. seyal, A. mellifera, A. etbaica, A. bussei, A. ehrenbergiana, A. laeta, A. tortilis, A. flava, A. giraffae, A. sieberiana etc. (Many of these species are widespread through the arid and semi-arid tropics of West, eastern and southern Africa). Both leaves and pods are used by various kinds of livestock and wild herbivores.

Many legume species are of great importance as browse, such as Buhinia rufescens, Entada africana, Pterocarpus lucens, Albizzia amara, Dichrostachys cinerea, Prosopis africana, Tamarindus indica and Dalbergia melanoxylon.

The Capparidaceae family possesses several excellent browse species Maerua crassifolia, M. angolensis, Cadabafarinosa, C. glandulosa, Boscia minimifolia, B. albitrunca, B. angustifolia, B. senegalensis and Capparis decidua.

Other important families are the Combretaceae (Combretum aculeatum, Anogeissus leiocarpus, Terminalia brownii), the Tiliaceae (Grewia tenax, G. bicolor, G. Yillosa), the Sterculiaceae (Sterculia setigera), the Rhamnaceae (Ziziphus mauritiana), the Anacardiaceae (Sclerocarya birrea, Lannea acida), the Rubiaceae (Mitragyna inermis, Feretia apodanthera), the Zygophyllacea (Balanites aegyptiaca, B. glabra, B. rotundifolia) and the Salvadoraceae (Salvadora persica).

Productivity of browse is not well known and very difficult to measure accurately. It may however be stated that it is closely related to rainfall and ecological zone, and varies from 100 kg to 1000 kg of edible DM/ha per year. The feed value of leaves, in terms of energy, is usually medium to low: 0.25 to 0.40 FU per kg of DM, i.e. 400 to 700 Kcal per kg of DM. Digestible protein is usually high, normally above 4%, often above 10%, and may sometimes reach up to 30%, especially in the Capparidaceae.

Fruits, especially pods of legume species, are high in metabolizable energy (1000 to 2000 Kcal per kg of DM) and contain 10 to 20% of DP in the DM.

The carotene content of browse is fair to high during the dry season when dried-out grasses have virtually none. Phosphorus, usually in scarce supply in tropical feeds, is relatively high in browse (1.5 to 2.5 g/ha of DM).

In comparing feed value of dried-out grasses and browse during the dry season, we obtain the figures shown in Table 1

Table 1. Feed value of dried grass and browse during the dry season

 

Net energy Kcal/kg DM

Digest. Protein g/kg DM

P g/kg DM

Ca g kg/DM

Caroter mg/kg

Dry grass straw

Browse

600–800

/1

/1

1.5–3.0

/1

400–700

56–300

1.5–2.5

2.5–20.0

50–800

Maintenance needs

700

50

1.3

2.5

1.5

This table shows that ruminants cannot meet their maintenance needs on dry grass alone. Since in the dry tropics the dry season lasts 6 to 9 months and there is usually no supplementary feeding, livestock and wildlife often depend entirely on browse to balance their diet in protein, phosphorus, calcium and vitamin A during this season. This has been shown by various experiments using herds feeding either on dry grasses or on dry grass and browse (Granier, 1976) and also using fistulated animals.

Using cattle with rumen fistulas, Blancou et al (1977) have shown in Senegal that browse represents an average of 25% of cattle diet during the dry season. This proportion grows as the dry season continues, from 5% at the beginning to 45% at the end. This result was obtained with cattle; one may expect the proportion of browse to be still greater with sheep and especially with goats and camels.

In northern Nigeria it was found that nomadic Fulani cattle spent 5% of their feeding time on browse during the rainy season and 15 to 20% during the dry season (De Leeuw, 1975).

Many pastoral groups in the arid and semi-arid tropics habitually lop branches from various forage species (Acacia seyal, in particular) to made the forage accessible to livestock during the dry season. This shows clearly that browse is perceived as a necessity by traditional herders.

2.3 In northern America

In the United States the area of shrub-dominated ecosystems is over 120 million ha (Forest Range Task Force, 1972); the total acreage of woody grazing land is in the vicinity of 320 million ha, most of them west of the Mississippi river (Plummer, 1972). The bulk of woody rangelands is made up as follows (after Plummer, 1972):

Southern desert shrubland                                                  144 million ha
Sagebrush/Atriplex, Great Basin                                           98 million ha
Juniper/pinyon woodland                                                        30 million ha
Salt desert shrub land                                                            28 million ha
Chaparral                                                                               12 million ha

In the great Basin, in the Shad scale/Sage brush complex (Atriplex confertifolia/ Artemisia tridentata) during winter time, shrubs make up 50 to 70% of the forage available and contribute 70% of the diet of sheep and 40% of the diet of cattle (Cook and Harris, 1968, in McKell and Malechek, 1978); the browse component is still higher for wildlife such as mule, deer, elk and pronghorn antelope, where it varies from 48 to 98% during the winter season (McKell and Malechek, 1978).

Protein, phosphorus and carotene content in browse is usually above the maintenance dietary need of livestock, whereas these nutrients are always well below maintenance requirements in dry grass (McKell and Melachek,1978); a fact also documented in the Mediterranean Basin and in tropical Africa, as already seen. However, dry grasses are usually higher in energy than browse, a tendency also observed in other parts of the world. Therefore, a balanced diet for cattle and sheep is composed of grasses (which bring the energy) and browse, which complements the diet in protein, phosphorus and carotene.

Important browse species in the Great Basin are (McGinnies, 1972):

Big sagebrush (Artemisia tridentata), Black sage (Artemisia nova), Little Rabbitbrush (Chrysothamnus stenophyllus), Big Rabbit brush (Chrysothamnus nauseus), Bitter brush (Purshia tridentata), Four wing Saltbrush (Atriplex canascens), Shad-scale (Atriplex confertifolia), Nuttal saltbrush (Atriplex nutallii), Winter fat (Eurotia lanata), Greasewood (Sarcobatus vermiculatus).

In the chaparral zone of western USA, the main shrub species are:

Scrub (Quercus dumosa), Leather oak (Quercus durata), Gambel oak (Quercus gambeli), Wavy leaf oak (Quercus undulata) Chamise (Adenostema fasciculatum), Manzanitas (Arctostaphlos sp. pl. (9 species), Buck brush (Ceanotus sp. pl. (10 species), Mountain mahogany (Cercocarpus sp. pl.), Service berry (Amelanchier sp. pl.), Locust (Robinia neomexicana, Rhus sp. pl., Prunus sp. pl.), Strawberry tree (Arbutus californica).

The southern desert shrub ecosystems are often dominated by unpalatable species, such as:

Creosote bush (Larrea tridentata), Opuntia sp. pl. (O. fulgida, O. spinosior; O. engelmani etc) Flourensia cernua, Carnegeia gigantea, Fouquiera splendens. However, palatable shrubs may be locally an important component in livestock diets. These are:

Four wing saltbush (Atriplex canescens), Mesquite (Prosopis juliflora) Spineless cacti (Opuntia ficus-indica, Opuntia robusta), Cercidium sp. pl. Acacia greggii and others.

2.4 In Latin America

Shrub-dominated ecosystems used as grazing lands cover huge areas. For instance the Cerrado and Caatinga of central-eastern and north-eastern Brazil, the coastal deserts and sub-deserts of Peru and Chile, the Chaco of Argentina, Paraguay and Bolivia, the Monte of Argentina, the Andean Puna of Peru, Bolivia, Chile and Argentina. As in other parts of the world, browse is mainly used by livestock outside the growing season when the weather is too cold or too dry (Soriano, 1972; Gasto'y Contreras, 1972).

Among the important browse species are:

Acacia sp. pl., Prosopis sp. pl., Cercidium sp. pl., Capparis sp. pl., Adesmia, Caesalpinia ferrea, Cassia excelia, Ziziphus jozeiro, Piptadenis sp., Lycium sp. pl., Chenopodim peniculatum, Atriplex coquimbana, Atriplex atacamensis, A. repanda, A. sagittifolium, Maytenus sp. pl., Grabowskia, Achatocarpus, Opuntia sp. pl., Pithecellobium dulcis, Lauhinia Cheilantha.

2.5 In Australia

The arid zone represents some 70% of the surface of the continent. About one third of the continent receives less than 250 mm of rainfall and is only used for extensive grazing. Browse or "top feed", as it is locally called, is an important component in extensive grazing systems and some 200 species of woody plants have been reported to be browsed by livestock (Everist, 1972), although only 40 of them are widespread throughout the continent and play a major role in the livestock industry. The browse ecosystems cover some 2.5 million km2 or 30% of Australia's land surface.

Some of the Australian browse species have been introduced to other continents and are artificially planted as forage, especially several species of Acacia, Atriplex and Maireana or Kochia.

The main grazing land ecosystems where top feed plays a major role are those dominated by the Mulga (Acacia aneura), which is the most important edible woody species in Australia and covers 1.5 million km2 or 20% of the continent (Everist, 1972). The Atriplex-Kochia communities on the saline soils of southern Australia occupy 0.2 million km2; the mixed gum trees (Eucalyptus) and Atriplex-Kochia communities of the Mallee cover 0.15 million km2. The mixed woodland communities of Eucalyptus/Acacia, with various browse species (Acacia, Cassia, Brachychiton, Rhagodia, Eromophila, Atalaya hemiglauca, ventilago viminalis etc), cover some 0.544 million km2.

Many studies on the digestibility and nutritive value of "top feed" have been carried out in Australia. In vivo as well as in vitro digestibility of five browse species from New South Wales may vary from 35 to 56% (Wilson, 1974). These figures are in agreement with those of Sarson and Salmon (1978) in North Africa. Protein content remains above the critical level even during drought periods, while the CP content in leaves (or phyllodes) and twigs virtually never drops below 6% and is often more than twice that much.

2.6 Selection of browse by herbivores

Selection of browse by herbivores depends on many factors; among them the feeding preferences of a given species of animal. Some species are primarily grazers while others are mainly browsers. Some are very strict concerning their diets others are more flexible or versatile.

Cattle, buffaloes, sheep, equines, wildebeest, most antelopes, gazelles, white rhino and hippo are mainly grazers but, as we have seen, especially in dry or cold seasons, grazers become browsers as well in order to balance their diet (Pratt and Gwynne, 1977).

Other species, such as goats, camels, eland, impala, kudu, elephant, giraffe, black rhino, deer, elk and many antelopes, are browsers to a large extent and can ensure normal growth on a pure browse diet.

It has been shown for instance that high-performance goats producing 1000 kg of milk in 300 days can still consume up to 30% of their diet in browse (Blanchemain, 1964). The same applies to camels; a female camel feeding entirely on browse may produce up to 3-6 kg milk per day, as opposed to 10-13 kg when feeding on fodder crops (Knoess, 1977).

This phenomenon has been clearly and satisfactorily explained by Sarson and Salmon (1978), in the following table showing the needs and quantitative intake potential per 100 kg of liveweight of cattle, sheep and goats (see Table 2).

Table 2. Needs and quantitative intake potential of cattle, sheep and goats

Maintenance needs F.U.

Cattle

Sheep

Goats

1.9

1.33

1.13

Quantity of DM ingestible (kg)

2.9

3.8

6.0a

Upper limit ratio F.U./kg DM

0.65

0.35

0.19

a According to French (1970) goats can ingest up to 8% of their body weight in DM daily, whereas cattle can hardly take 3%.

As the nutritional value of browse varies from 0.25 to 0.40 FU per kg of DM, browse alone cannot ensure the maintenance requirements of cattle (0.65 FU/kg of DM). Browse can ensure maintenance of sheep (0.35 FU/kg of DM), but does not allow production. In goats, however, maintenance and production can be assured on a pure browse diet (0.19 FU/kg of DM). This explains why only goats, camels and some wild herbivores can survive on the depleted rangelands often found in arid zones, where browse constitutes most of the feed. This is also why goats and camels are less affected by catastrophic droughts than sheep and cattle.

2.7 Management of browse ecosystems

Sound management of ligneous rangeland, especially in arid zones or in cold winter areas, requires optimum balance between grazing and browsing. Since neither grazing nor browsing alone can ensure year-long productivity of sheep and cattle under these conditions, the optimum number of fodder shrubs and trees should be kept such that a state of equilibrium is maintained.

Too many trees and shrubs often decrease the productivity of the grass layer. Conversely, the elimination of browse species leaves livestock extremely vulnerable to prolonged droughts and with an unbalanced diet during the dry or cold season, unless expensive supplementary feeding is provided.

The art of management thus consists in maintaining a desirable equilibrium whereby browse provides 20 to 30% of the livestock diet during the dry season, i.e. 20 to 30% of the herbage production. Desirable density and ground cover depend on many factors: climatic, edaphic and topographic conditions, and the specific size and shape of the desired ligneous species. For Atriplex repanda in central Chile the optimum density/productivity ratio is 4000 shrubs per hectare, with an average rainfall of 300 mm (Gasto, 1978). In Tunisia, with Atriplex nummularia and rainfall of 200–399 mm, the optimum number is 2000 shrubs per hectare. In West Africa a density of 25–50 trees per hectare is considered an optimum in the Acacia albida millet systems, with a canopy cover of 30–60%. In the arid to sub humid savannas of West Africa a density of 100 to 400 trees and shrubs per hectare, depending on average precipitation, is considered an optimum from the range management point of view (Bille, 1978).

It should be added that grass production in the arid zone is often much higher, of better quality, and lasts longer under the shade of fodder trees. This is the case in the Sahel region of West Africa, where productivity of Pennisetum pedicellatum in the shade is about double that on open ground, and the grass under the trees dries out 3 to 6 weeks later. Photosynthetic efficiency is 1.4% under shade and 0.3% in the open in the arid zone of Senegal (Bille, 1978). The same has been observed with Panicum maximum (Pratchett, pers. comm.) in Botswana, where potential evapotranspiration is reduced by 50–70% in the shade and the grass remains green 6 weeks longer at the beginning of the dry season.

However, in some instances, especially where ligneous species are unpalatable (Eucalyptus or Melaleuca in Australia, for instance), the removal of woody vegetation may increase herbage yields tremendously. This has been documented in the USA, for instance in the Californian Chaparral, as well as in the Mediterranean basin (Etienne, 1976).

3. Plantation of fodder shrubs and trees as fodder reserves

A number of fodder shrubs and trees have been used for centuries, often for other purposes; such is the case of the cacti Opuntia spp. primarily cultivated for their fruits for centuries, but as a fodder crop only since the beginning of the present century. Mulberry trees (Morus albs) have been cultivated from time immemorial both for their fruit and as feed for silkworms, while the Vitis vinifera has also been used for centuries as fodder only in periods of scarcity. The same applies to the olive species and the carob.

For some 60-80 years, with the improvement in reaforestation techniques, a number of wild land species have become domesticated and cultivated for their fodder value, due to the fact that they remain green in spite of long periods of drought, because of their ability to use layers of moisture in the soil or ground water at depths which are inaccessible to conventional fodder crops. They are also valued for their ability to grow on shallow or stony soils, or on steep slopes where conventional fodder species cannot be established, and for their adaptation to arid conditions where conventional forage species cannot survive.

In arid and semi-arid zones almost all over the world rangelands are being rapidly depleted (FAO, EMASAR conference, 1974. UNCOD, desertification conference, 1977). Cultivation is also expanding at the expense of rangelands in many parts of the world. Moreover, irrigated fodder crops are very rarely available since water is expensive and animal production cannot, in most cases, compete economically with cash crops, vegetables and industrial crops, dairy production in the vicinity of urban areas is an exception, however livestock production in the arid and semi-arid zones (which probably contain about 50% of the world's livestock population) is consequently becoming an increasingly difficult and unproductive occupation.

One of the remedies to this situation is to grow drought resistant fodder shrubs and trees under rained conditions. Such ligneous fodder crops occupy large areas, probably over several million hectares in the world today, are increasing rapidly in countries like the USSR, Iran, South Africa, Syria, Brazil and those of North Africa.

The main species which are at present cultivated on a large scale are the following:

Spineless cactuses (Opuntia sp. pl.), Salt bushes (Atriplex sp. pl.), Acacias (Acacia sp. pl.) Leucaena (Leucaena Leucocephala), Mesquites (Prosopis, sp. pl.), Honey locust, (Gleiditschia triacanthos), Carob (Ceratonia siliqua), Olive (Oleae europaea), Calligonum (Calligonum sp.), Saxaouls (Haloxylon persicum), (Haloxylon aphyllum), Salsola (Salsola sp. pl.), Sage brush (Artemisia sp. pl.), Mulberry (Morns albs).

3.1 Spineless cacti

Spineless cacti have been cultivated as fodder crops in the southern states of the USA, Texas, New Mexico, Arizona, California, since the end of the last century (Griffiths, 1906, 1907, 1908, Hare and Griffiths, 1907, Hare 1908). The main varieties cultivated were the spineless forms of O. ellisiana, O. ficus and O. inermis. Forage yields were 25 to 130 tons of green fodder/ha per year, according to Griffiths.

In Mexico, wild land cacti, most of them spiny and including, O. streptacantha, O. leucothicha, O. chrysacantha, O. lindheimeri, O. phoeacantha and O. amyclalea) cover some 5 million ha. The following varieties are mainly developed in the central highlands of San Luis Potosi and Zacateca and are used for their fruit: O. streptacantha and O. leucotricha, and O. amyclaea. An unknown acreage of fodder plantations of spineless types of O. ficus indica and O. robusta has been established and is reported to produce 25 to 125 tons of fresh matter per hectare/year (Lozano, 1958; Rojas et al, 1966).

In north eastern Brazil over 300 000 ha of cacti are grown as a fodder reserve for the dry season. Three species are used for this purpose: O. ficus indica, Nopalea cochenillifera and O. inermis; yields of 100 to 260 tons of fresh matter per ha/year have been reported by various authors (Correa de Souza, 1963 and 1965).

In South Africa, large areas are devoted to fodder cacti plantations, especially in the arid zone between the 150-300 mm isohyets (Maré, 1932 and 1953; Bonsma and Maré, 1942; De Kock, 1965).

Noxious spiny prickly pear (mainly O. megacantha), has been eliminated over almost 1 million ha through biological control using Cactoblastis cactorum and Dactylopus opuntiae. Spineless cochenilla-resistant forage varieties were subsequently developed, these are: O. robusta, C. V. robusta, C. V. monterrey, C. V. chico and O. fusicaulis.

Fodder cacti, in conjunction with old-man saltbush, are used as emergency feed for sheep in the dry season. They provide emergency feed for 20 to 25 sheep per ha of cactus and saltbush, the yields of cactus recorded varying from 20 to 100 tons of fresh matter per ha/year.

In North Africa there are probably over 300,000 ha of spineless cactus plantations (O. ficus indica). In Tunisia alone, over 80,000 ha have been planted with government grants and loans during the past decade, while the total area covered in this country is probably over 150,000 ha, mostly located between the 200–400 mm isohyets. Large areas are also being planted in the arid zones of Libya, Algeria and Morocco as part of livestock development projects. In Sicily spineless cacti are grown over 100,000 ha and are partly cultivated for fruit and partly for fodder.

In all, probably over one million hectares of spineless cacti are cultivated in the world today as emergency fodder crops and used as such in drought-evading strategies in the arid zones of Brazil, South Africa and North Africa.

However, the use of cacti is hampered by some serious limitations: cacti are nutritionally unbalanced: they are rich in carbohydrates, vitamins and ash but deficient in protein and phosphorus. Consumption by ruminants of large quantities of fresh cacti without additional roughage often provokes diarrhea after a few days and thus limits the intake. This limitation is nevertheless balanced by important advantages and can be easily avoided. Some considerable advantages are that production of cacti in the arid zones is extremely high as compared with other plants, and that water content of the cladodes varies from 80% during the dry season to 90% during the growing season. Cattle and sheep can consume up to the equivalent of 10% of their body weight in fresh cactus daily as long as 0.1% of this weight is added in the form of dry roughage (straw or hay) (Monjuze and Le Houérou, 1965). Moreover, sheep can be fed for many months, with a slight weight gain, on a diet based on cactus, wheat straw and urea only (Delhaye, Sarson and Le Houérou, 1974). According to Cordier (1947) and De Kock (1965), cattle and sheep can live on cactus alone for about 200 days (Cordier, 1974; De Kock, 1965). Sheep on a cactus diet may be deprived of watering for very long periods (up to 525 days according to De Kock); and a similar conclusion emerges from experiments by Cordier (1974). However, according to the latter author, watering cannot be entirely suppressed for cattle feeding on cacti although it may be greatly reduced.

The above conclusions on the use of spineless cacti as animal feed is the result of numerous experiments and long practical experience, especially in the USA (Woodward etal,1915; Griffiths, 1907; Hare and Griffiths, 1908), in South Africa (Marι, 1932, 1935; Marais, 1935; Bonsma and Marι, 1942; De Kock, 1965, etc.), in Tunisia (Cordier,1947; Theriez 1966) and in Italy (Maymone and Maloscsini; 1961).

Cacti are nevertheless subject to certain ecological limitations within the arid zone. They cannot grow, for instance, in the Sahel region of West Africa (Peyre de Fabregues, 1966) except on a very narrow coastal strip, because of the very low air humidity in this region for 6 to 9 months every year. Cacti cannot withstand average air humidity below 40% for more than one continuous month. They are also limited by winter temperatures wherever the average minimum temperature of the coldest month is below + 1 °C, as it is in the highlands of North Africa, in large parts of the Near and Middle East.

3.2. Saltbushes (Atriplex sp.pl.)

Chenopodiaceae saltbush varieties are native to almost all the arid zones of the world (Europe, Africa, Asia, America and Australia). There are some 300 species of which about 50 are considered as fodder shrubs. Not more than 10 species are actually cultivated as fodder crops. These are: Atriplex nummularia: old man saltbush, originally from Australia and now cultivated in many arid zones of the world. Atriplex canescens: four wing saltbush from north America, also cultivated in the Near and Middle East and North Africa. Atriplex halimus: from the Mediterranean basin, also cultivated in many other arid zones. Atriplex vesicaria: bladder saltbush from Australia, Atriplex semibaccata: from Australia, a creeping saltbush, Atriplex glauca: from the Mediterranean, Atriplex lentiformis: from the Western USA, Atriplex repanda and Atriplex atacamensis: from Chile, Atriplex rhagodioides: from Australia.

These varieties are extremely drought resistant and can grow on heavy and saline or alkaline soils with average rainfalls as low as 150 mm. They can survive for a whole year with only 50 mm of rain (Franclet and Le Houérou,1971). They are quite resistant to frost, especially A. canescens, and can withstand temperatures of -10 to 15°C. Their establishment, either from seedlings or from seeds, is usually easy and quick, and they reach maturity in 2-3 years. Their feed value is high, with a CP content of 15 to 25% of DM for leaves and twigs. Productivity is also high, although lower than that of cacti.

However, saltbushes have their ecological and feeding limitations, they are not adapted to some dry tropical zones such as the West African Sahel. Their sodium chloride content may be a serious limitation wherever drinking water is scarce or saline. They, nevertheless, provide an excellent protein-rich complement to cacti, as shown in both North and southern Africa. Other promising Chenopodiaceae are Chenopodium auricomum from central Australia and Chenopodium paniculatum from Chile.

3.3 Acacia

The acacia genus probably consists of over 900 species spread over most of the arid and tropical zones of the world (Vassal, 1972). About 50 species are thought to be used in reafforestation and sand dune fixation at present, of which a dozen are considered good fodder crops. These species include the Australian wattles— Acacia saligna ( = A. cyanophylla), extensively used in North Africa and the Near East, A. aneura, A. ligulata, A. victoriae, A. pendula, A. Cyclops, A. melanoxylon and A. salicina —and the African thorns— Acacia albida ( = Faidherbia albida) from West, East and southern Africa, Acacia tortilis ssp. tortilis and ssp. raddiana, and Acacia nilotica ssp. indica from the Middle East.

Unlike saltbushes, many species of Acacia are adapted to sandy habitats and therefore are also used in sand dune fixation. Browse productivity from leaves, twigs and pods is good and usually falls somewhere between that of cacti and saltbushes.

Palatability varies from species to species and even from each individual tree to the next within any species or population. However some species, such as A. saligna, A. albida, A. senegal and A. nilotica indica, are planted as browse over extensive areas. A. albida in particular has been used for centuries in traditional agropastoral systems in Africa in conjunction. Much research has been devoted to this agropastoral system, which demonstrates that the shedding of the leaves of Acacia albida is equivalent to a fertilisation of about 50 tonnes of manure per ha/year, i.e. 75 kg N,12 kg P,13 kg K, 20 kg S, 25 kg Mg and 120 kg Ca per ha/year (Giffard, 1964), for an average density of 50 trees per ha. This explains the maintenance of the productivity of these agropastoral systems over the centuries. A yearlong stocking rate of 400 kg of liveweight per ha or 3 million kcal/ha/year have been recorded in such systems with a high density of 50 trees/ha, in addition to millet production of 1000 to 1500 kg of grain per ha/year in Senegal, with an average rainfall of 650 mm (Charreau,1970). Similar production figures (equivalent to a yearlong stocking rate of 8–10 sheep per ha) have been recorded on Acacia cyanophylla fodder plantations in Israel and in Tunisia (Le Houérou, unpublished), with annual rainfall of 200–400 mm. As may be expected from legume species, browse from Acacia is rich in protein and phosphorus but low in carbohydrates (Sarson and Hamrouni, 1974).

3.4 Leucaena

Leucaena leucocephala (L. glauca) is a legume forage tree of the sub-humid and humid tropics (600–1800 mm of average rainfall) and a native of Central America. Large plantations of this highly nutritious fodder yield 2 to 20 tonnes of dry matter browse per ha/year, i.e. equivalent to 800-4300 kg of protein per ha/year (Vietmeyer and Cottom,1977). Protein content is similar to Lucerne, (25% CP), carotene is much higher (500 mg/kg DM versus 250), Leucaena is slightly richer in energy (68 versus 56 TDN), while phosphorus and calcium are slightly lower than in alfalfa.

However, Leucaena contains a toxic amino-acid, mimosine, which provokes sickness in ruminants when the diet includes more than 30% of Leucaena (DM). With this restriction, cattle performance on Leucaena-supplemented pastures is considered excellent; palatability and digestibility are high (50–70% for the latter). Weight gains of 1 kg/day with steers have been recorded in Queens land on pastures based on Setaria anceps and Leucaena, about twice as high as may be expected from a good conventional tropical pasture. Commercial meal from Leucaena is being produced on a large scale (6400 tonnes in 1974) in Malawi and the projections for 1980 are 13,000 tonnes produced from 1200 ha (Savory and Beale, 1974).

The three main cultivars are Hawaii, Salvador and Peru, in order of increasing productivity. Low mimosine cultivars (C.V. Cunningham) are being developed by CSIRO in Queens land (Hutton and Beattie, 1976).

3.5 Mesquites (Prosopis spp.)

Several species of Prosopis are planted as fodder crops in various and zones of the world, especially P. chilensis and P. juliflora (P. dulcis) in the dry tropics of Africa and the Middle East, P. tamarugo in Chile and P. cineraria (P. spicigera) in Pakistan, India and the Persian Gulf. The latter is used in the same way in India and Pakistan as Acacia albida in Africa, i.e. as a fodder tree scattered in millet fields. Branches are lopped and fed to livestock which also gather the fallen pods. Prosopis species are quite similar to Acacia for the nutritive value of leaves, twigs and pods. Some 30,000 ha of the phreatophyte Prosopis tamarugo were planted during the past decade in the northern desert of Chile, with a density of 100–120 trees per ha; yields of 50–100 kg of pods per tree, i.e. 5000 to 10000 kg/ha/year are reported in adult stands, with stocking rates of 10–20 sheep ha/year.

3.6 The honey locust, Gleiditschia triacanthos

The honey locust from North America, has been planted in various places in the semi-arid zones and especially in the Mediterranean basin, for the forage quality of its pods. The tree is well adapted to semi-arid conditions with cold winters.

3.7 Carob

Ceratonia siliqua is a common tree in the areas of the Mediterranean basin having mild winters. The pods are traditionally used for feeding livestock, especially horses and pigs. Commercial plantations of improved varieties have been developed in Cyprus, where the pods are used in the pharmaceutical industry. Small plantations are found here and there in the Mediterranean islands, Sicily, Malta and the Aegean islands.

3.8 Other legume species

Other legume species are used on a small scale, e.g. Medicago arborea or tree medic, from the eastern Mediterranean, with an ecology and feed value comparable to alfalfa. Yields reported in Tunisia are of the order of 4000-8000 kg of consumable DM/ha/year between the 300 and 400 mm isohyets. These yields allow a potential stocking rate of 6-12 sheep per ha (Sarson and Hamrouni, 1976). Coronilla glauca, another species used, has a similar ecology, feed value and productivity as that of tree medic.

Cassia sturtii, introduced from central Australia to Israel, was found extremely drought resistant and highly palatable to all kinds of livestock in the Northern Negev. Yields are reported to be about 1000 kg DM/ha/year of protein-rich browse (12% CP), with rainfall of only 200 mm (Meyer Forti, 1971).

3.9 Olive

The olive is not usually planted for browse, but all over the Mediterranean basin twigs and leaves are pruned and fed to livestock. They are readily consumed by cattle, sheep, goats and camels. Production of browse is about 10–20 kg per tree/ year, i.e. 200 to 2000 kg/ha/year. Feed value is fair to good in protein, phosphorus and calcium, but on the low side in energy: 400–450 kcal per kg of DM. As olive groves occupy about 8 million ha (or 800 million trees) in the world today, global forage production is in the order of 8 million tonnes of DM/year. This is equivalent to the annual dietary requirement of 15 million sheep.

3.10 Calligonum

Several species of these desert-dune shrubs of the Polygonaceae family are used in sand dune fixation and sown for pasture rehabilitation in various and zones of the world (Nechaeva and Prikhodo, 1968): they include Calligonum polygonoides (Iran), C. arborescens, C. pellucidum, C. elatum, C. eriopodum C. caput medusae and C. setosum (USSR), C. comosum (Libya), C. comosum, C. azel and C. arich (Tunisia). Establishment is usually ensured by direct sowing. Palatability is high but feed value is not well documented.

3.11 Saxaouls

Haloxylon persicum, and to a lesser extent H. aphyllum (H. ammondendron), are used for and land and pasture reclamation in various parts of the Near East (Iran, Jordan, Saudi Arabia, Iraq) and the USSR. Palatability is fair and drought resistance is extreme (as for Calligonum). Successful establishment has become a matter of routine under conditions with less than 100 mm of annual precipitation in Iran, for instance (Shaidae and Niknam, 1973; Le Houérou, 1975). Establishment is ensured either by seedlings or by direct sowing.

3.12 Salsola

Several species of this Chenopodiaceae are being used for pasture rehabilitation through reseeding in the USSR (Salsola paletskiana, S. richteri) and in Syria (S. vermiculata).

3.13 Sagebrush

Artemisia spp., sagebrush, has been used for pasture rehabilitation on a large scale in the arid zones of the USSR (Artemisia badhysi, A. turanica). A promising species for reseeding depleted ranges in the arid Mediterranean zone is Artemisia herbs albs.

3.14 Mulberry

Morus alba, M. japonica are widespread in the Mediterranean semi-arid to humid zone, where they were traditionally used for cultivated silkworm feeding. Mulberry is also well adapted to semi-arid tropical conditions, especially in elevations above 1000 m. It thrives in the highlands of East Africa.

Yields of mulberry are quite high and feed value is exceptional; it is superior to most conventional fodder crops, including alfalfa. It has high digestibility (70%), high energy content (0.7 FU/kgDM or 1155 kcal/kg/KM), very high protein content (18–22% digestible protein), and is very rich in phosphorus (0.4%) and in carotene.

Mulberry is best used in montane areas on small farms where labour is not in short supply. However, dwarf varieties have been developed in Japan which allow for mechanical mowing and harvest.

3.15 Establishment and management techniques

Table 3 shows establishment and management techniques for some of the species discussed above.

Table 3. Establishment and management techniques

                              Establishment

Management

Species

Direct sowing

Planting nursery grown seedlings

Vegetative propagation

Direct browsing

Cut and carry

Cacti

–

–

+c

–

+

Saltbushes

(+)a

+

+e

+

–

Acacia

(+)b

+

(+)e

+

(+)

Leucaena

+

+

+d

+

+

Mesquite

(+)f

+

–

+

–

Honey locust

+

+

–

+

–

Carob

+

+

–

+

–

Olive

–

–

+

+

+

Calligonum

+

(+)

(+)

+

–

Saxaouls

+

(+)

–

+

–

Salsola

+

–

–

+

–

Sagebushes

+

–

–

+

–

Cassia sturtii

–

+

+

+

+

Tree medic

+

+

+

+

+

Coronilla

+

+

+

+

-

Mulberry

+

+

+d

+

+

+ Usual technique
(+) Locally used
a Only a few species may be established by direct seeding: A. canescens, A. glaucal, A. semi baccata occasionally A. halimus. Mechanical sowing has been experimented (Orev, 1971; Malcolm, 1976).
b Some species may be directly sown, such as A. senegal.
C Plantation of joints (cladodes, occasional grafting).
d Cuttings, stumps.
e Occasionally cuttings (A. nummularia, A. halimus), especially in the multiplication of higher palatability strains.
f Whether the species is self-reproducing or not varies according to area.

3.16 Cost of establishment and management

Costs vary widely from country to country and according to the techniques used and the cost of labour. Direct sowing is usually cheaper, especially when mechanical sowing is possible.

The cost of establishment of Acacia and Atriplex in North Africa and the Near East is around US $ 150–300 per ha, including the cost of operating a nursery. The plantation itself requires 20 to 25 mandays per ha. In North Africa, the cost of establishing cactus plantations is about the same of which 70 to 80% is accounted for by labour. Cost of utilization is about US $ 80–100 per ha/year, about 80% of which is accounted for by labour.

Reckoning on an average minimum production of 25 of fresh cacti per ha/year in arid zones, (200-300 mm) and a depreciation period of 25 years the cost would be US $ 3 per tonnes of fresh cactus or US $ 0.02 per kg of DM or US $ 0.14 per FU.

Under higher rainfall (300-500 mm) production would be at least three times greater and cost per FU about half the above figure. Cactus plantations are labour demanding and are therefore of special interest in areas where labour is plentiful and cheap, as in many developing countries. The same applies to mulberry and Leucaena.

In Malawi, high-yielding plantations for meal production require about 2 man-years per ha (Savory and Beale, 1974).

3.17 Use of fodder shrubs and trees for reclamation of marginal land

Fodder shrubs and trees are extensively used in marginal zones (mountains, arid and semi-arid zones) as a means of controlling either water or wind erosion, to reclaim degraded rangelands and rehabilitate soils degraded by salinity or alkalinity and for sand dune fixation. Large-scale projects have been successfully carried out in many countries, for instance in Iran, using Atriplex canescens, A. lentiformis, Haloxylon persicum and H. aphyllum, in Chile with Prosopis tamarugo; in South Africa with Cacti and salt bushes; in North Africa with Cacti, saltbushes and Acacia; in tropical Africa with Acacia albida, A. Senegal, A. aneura and A. nilotica ssp. indica etc. Some countries like Tunisia and Libya have promulgated legislation ensuring government grants and loans to farmers who establish such plantations. This type of action becomes more and more necessary as rangelands in marginal areas are becoming increasingly depleted by overgrazing, fuel gathering and the expansion of cereal cultivation. However, it should be stressed that reclamation of marginal lands by fodder shrubs and trees, although presenting no difficult technical or economic problems, is faced with serious bottlenecks in terms of management and utilization due to the social conditions prevailing in many of the countries concerned.

On the other hand, successful biologically balanced systems have been set up in traditional peasant civilizations such as the one based on Acacia albida — millet in West Africa, or Prosopis cineraria — millet in Rajasthan.

In developed countries, such as the USA or Australia, native shrubs and trees are being increasingly used for landscaping (highways), recreational activities and game preservation or restoration. Similarly, some forage shrubs are used for the prevention of fire hazards. Such is the case of Atriplex in the California Chaparral. Saltbushes, which have a high ash content, have a very low flammability and are thus useful as fire breaks.

6. Conclusions

Desertification is at present a direct threat to the welfare of 200 to 300 million people in various arid zones of the world. If the present trend is not reversed, by the end of the present century one third of the land cultivated today will be made useless to man (United Nations International Desertification Conference, 1977). The areas undergoing desertification are in excess of 40 million km2, i.e. almost 30% of the earth's surface (in addition to 8 million km2 of actual climatic deserts). Additionally, erosion is progressing at a frightening pace, especially in the montane areas of tropical and subtropical zones.

This dramatic situation is due not to any climatic change or natural catastrophe, but to the misuse of land and natural resources, often provoked by an overwhelming population pressure. Pressure on land has frequently risen far beyond its carrying capacity under traditional management practices.

At the same time, as more and more productive land is lost, food supplies, especially animal products (protein), are in increasing shortage in developing countries. Expanding irrigation has so far been the main reaction to this situation. Some 200 million ha are under irrigation at present (1.6% of the total land surface), while potentially irrigable land is estimated at 470 million ha (3.5% of the total land surface, which is 134 million km2) (Buringh et al, 1975), out of currently salinity and alkalinity (Kovda,1972). The potentially irrigable areas thus represent less than 10% of the land in the arid and semi-arid zones; this means that over 90% of the land has to be reclaimed by other methods. What is proposed here is a new approach to farming based on biological and ecological principles of optimum land use under long-term sustained productivity. These principles imply a balance between the various farming activities, forestry, crop and animal production, and their proper integration. These principles are not new; they have often been advocated in the past, but very rarely applied.

As far as forestry on rangelands is concerned, management should aim at keeping a balance between browse species and grasses, especially on marginal land and in arid zones, since as has been seen, grasses alone cannot meet the dietary needs of livestock during the dry or cold season, and browse can efficiently complement this deficiency but is too low in energy for high-performance livestock when used alone.

Fodder trees and shrubs have been successfully planted over several million hectares, especially in arid and montane areas. Such plantations should be expanded in the context of drought evasion strategies which aim to maintain a balance between livestock requirements and feed supplies during extended dry periods. Increased populations of trees and shrubs would also make it possible to transform pastoral nomadic or transhumant animal production systems into settled agropastoral systems, as has already been achieved on a small or intermediate scale in several countries. Such systems, based on permanent feed supply from fodder shrubs and trees, can ensure settled animal production systems in arid zones and montane areas where grazers traditionally roam about in search of pastures and water.

Furthermore, the planting of fodder shrubs and trees is an efficient means of controlling water and wind erosion, fixing sand dunes, combating desert encroachment and restoring sterile land to production. Former irrigated land which has become sterile due to salinity can be restored to productivity by planting fodder saltbushes. The same saltbushes can also make use of soils and water which are too saline for conventional crops.

Enough knowledge and experience has been gained and disseminated throughout the world for the past 50 years to enable these problems to be tackled rationally. However, political and social constraints have so far prevented their application on a broad scale, with the exception of a few countries. Lack of efficient organization and extension services, rather than financial resources, seem to be the main bottleneck to the application of this development strategy.

There is no doubt that tremendous progress could be achieved through better coordination at national and international level between agronomists, foresters and range/livestock specialists on the one hand, and sociologists, administrators, politicians and financial agencies on the other in order to plan and implement sound, balanced development schemes.

However, further research is still needed to gain a better understanding of the biology of browse species and the dynamics of native browse ecosystems in order to attain optimum multiple use of forest and rangeland. Genetic improvement of ligneous fodder crops is also needed, to increase their palatability and their feed value, and to find new strains adapted to specific climatic or soil conditions.

References

Bille, J.C. (1977). 'Etude de la production primaire nette d'un écosystème Sahélien'. Trav. et doc. de l'ORSTOM, n° 65, Paris.

Bille, J.C. (1978). 'Rôle des arbres et arbustes en tart que source de protéines daps la gestion des pâturages d'afrique Tropicale'. Mimeo. Supporting paper, item no. 10, 8th, World Forestry Congress Jakarta.

Blanchemain a. (1964). 'Conditions et possibilités pour un meilleur élevage de chévres'. Mimeo. Goat Raising seminar, Rome, FAO.

Blancou, J. et al (1977).'Composition du pâturage naturel consommé par les bovins en milieu tropical: Note sur une technique d'étude nouvelle'. Mimeo. Colloquee sur les recherches sur l'élevage bovin en zone tropicale humide, Bouaké, Côte d'Ivoire.

Bonsma, H.C., Maré, T.S. (1942).'Cactus and oldman saltbush as feed for sheep'. Bull. 235, 72 p. Pretoria, Dept. of Agriculture and Forestry.

Brinkman, W.L. De Leeuw, P.N. (1976)). 'The nutritive value of browse and its importance in traditional pastoralism'. Mimeo, Agricultural Research Station, Shika, Ahmadou Bello, University, Zaria, Nigeria.

Buringh, P. et al (1975). 'Computation of the absolute maximum food production of the World'. Department of Tropical Soil Sciences, Agricultural University.

Charreau, c. (1970). 'L'amélioration du profit cultural daps les sots sablo-argileux de la zone tropicale ouest africaine et ses incidences économiques'. Mimeo. Centre National Recherche Agronomique, Bambey, Sénégal.

Charreau, C., Vidal, P. (1965). 'Influence de l'Acacia albida sur le sol: nutrition minérale et rendement des mils Pennisetum'. L Agron. Trop. Paris. 67, 600–626.

Cook, C.W. (1971). 'Effects of season and intensity of use on desert vegetation'. Bull, Utah Agricultural Experimental Station, Utah State University, Logan.

Cook, C.V. (1972). 'Comparative values of forbs, grasses and shrubs'. In: McKell, Blaisdell and Goodin (eds). Wild land shrubs, their biology and utilization. USDA Forest Serv. Gen. Tech. Rep. INT-1.

Cordier, G. (1974). 'De la composition de quelques produits fourragers tunisiens et de leur valeur pour l'alimentaitondu mouton'. Ann. Serv. Bot. Agron., 20:25–108. Tunis.

Correa de Souza, A. (1963). `Revisao de Conhecimentos sobres as Palmas forrageiras'. Bol. no. 5, Recife.

Correa de Souza, A (1965). `Novos experimentos con Palmas forrageiras em Pernambuco'. 9th International Grassland Congress, Sao Paulo.

De Kock, G.C. (1965). 'The breeding of spineless cactus as a drought resistant fodder crop'. 9th International Grassland Congress, Sao Paulo.

De Kock, G.C. (1965). 'The management and utilization of spineless cactus'. 9th International Grassland Congress, Sao Paulo.

De Leeuw, P.M. (1975). 'Species preferences of domestic ruminants grazing Nigerian savanna'. Memeo, Agric. Res. Stn. Shika, Ahmadou Bello, Univ., Zaria, Nigeria.

Delhaye, R., Le Houérou, H.N., Sarson, M. (1974). 'Amélioration des pâturages et de l'élevage au Hodna (Algérie)'. PNUD/FAO, ASG: DP/ALG/66/509, Rome, FAO.

Dietz, R. (1972). 'Nutritive value of shrubs'. In: McKell, Blaisdell and Goodin (eds). Wildland shrubs, their biology and utilization. USDA For. Serv. Gen. Tech. Rep. INT-1.

Etienne, M. (1978). 'Amélioration des conditions de parcours et des pâturages naturels pour la production de protéines animates en zone montagneuse de Corse'. Mimeo, Vol. Contro., Item no. 10, 8th World Forestry Congress, Jakarta.

Everist, S.L. (1969). 'Use of fodder trees and shrubs'. Advisory Leaflet no. 1024. Brisbane, Queensland Dept. of Primary Industries, Div. of Plant Industry.

Everist, S.L. (1972). 'Australia'. In: McKell, Blaisdell and Goodin. Wildland shrubs, their biology and utilization, USDA Forest Serv. Gen. Techn. Rep. INT-1.

FAO (1974). 'The ecological management of arid and semi-arid rangelands in Africa and Near and Middle East'. Report of an expert consultation AGP: Misc/26, Rome, FAO.

FAO (1975). 'The ecological management of arid and semi-arid rangelands in Africa and the Near and Middle East'. Formulation of an international cooperative programme. Report of an International Conference; 19p., FAO, Rome.

Forti, M. (1971). 'Introduction of fodder shrubs and their evaluation for use in semi-arid areas of the Northern Negev'. Mimeo. Israel, Negev Inst. for Arid Zone Research Been-Sheva.

Franclet, A.; Le Houérou, H.N. (1971). 'Les Atriplex en Tunisie et en Afrique du Nord'. FAO: SF/TUN 11, Tech. Rep. no. 7 Rome, FAO (French and English versions).

French, M.H. (1970). 'Observations sur la chévre'. Rome, FAO.

Gasto, J. (1978). 'Les arboles y arbustos en el manejo de pastos naturales, con referencia particular a la prduccion de proteina'. Mimeo. Supporting paper item no. 10, 8th World Forestry Congress, Jakarta.

Gasto, J.; Contreras, D. (1972). 'Analisis del potential pratense de Fanerofitas y camefitas en regiones mediterraneas de pluviometria limitada'. Bull. Tech. no. 35: 30–59 Santiago Fac. de Agron., Univ. de Chile.

Giffard, P.L. (1964). 'Les possibilités de reboisement en Acacia albida au Sénégal'. Bois et forets des tropiques, 95:21–33.

Giffard, P.L. (1972). 'Rôle de l'Acacia albida dans la régénération des sots en zone tropicale aride'. 7th Congrés Forestiére Mondiale Buenos Aires.

Granier, P. (1975). 'Note sur l'introduction des techniques d'amélioration de la productivité de l'élevage en zone sahélienne'. Mimeo. Maisons Alfort, IEMVT.

Griffiths, d. (1966). 'Feeding prickly pear to stock in Texas'. Bur. of Anim. Industry, Bull. no. 91, Washington D.C.

Hare, R.F. (1908). 'Experiments of the digestibility of prickly pear by cattle'. Bur. of Anim. Industry, Bull. no. 106, pp. 7–38, US Dept. of Agriculture, Washington D.C.

Hutton, E.M., Beanie, W.M. (1976). 'Field characteristics in three boxed lines of the legume Leucaena leucocephala'. Trop. Grassland, 10: 187–194

Knoess, K.H. (1977). 'The camel as a meat and milk animal'. World Animal Review, 22: 3–8, FAO, Rome.

Kovda, V.A. (1972). 'The world's soils and human activity'. In: N. Polunin (ed.) The environmental future. New York, Macmillan.

Kovda, V.A. (1974). Biosphere, soils and their utilization. Moscow.

Le Houérou, H.N. (1971). 'The useful shrubs of the Mediterranean basin and the arid tropical belt south of the Sahara'. Mimeo, AGPC: Misc/24, Rome, FAO.

Le Houérou, H.N. (1972). 'Africa: The Mediterranean region'. In: Mckell Blaisdell and Goodin (eds). Wildland shrubs, their biology and utilization. USDA Forest. Serv. Gen. Tech. Rep., INT-1.

Le Houérou, H.N. (1976).'Rehabilitation of degraded arid land'. In: Rapp, Le Houérou and Lundholm (eds). Can desert encroachment be stopped? Ecological Bulletin no. 24, Secret. for Internat. Ecology, Stockholm.

Le Houérou. H.N. (1977). 'The grassland of Africa: classification, production evolution and development outlook'. International Grassland Leipzig, and Addis Ababa, International Livestock Centre for Africa. Mimeo.

Le Houérou, H.N., Hoste, Ch. (1977). 'Rangeland production and annual rainfall relations in the Mediterranean basin and in the African Sahelo-Sudanian zone'. J. Range Manage., 30 (3): 181–189, May 1977.

Liacos, G.L., Moulopulos, Ch. (1967). 'Contribution to the identification of some range types of Quercus coccifera'. University of Thessaloniki.

Long, G. t al (1967). 'Essai de détermination expérimentale de la productivité dune garrique à Quercus coccifera'. Mimeo. Doc. no. 209, Montpellier CEPE/CNRS.

Marais, J.C. (1935).'Drought resistant fodder crops'. Farming S. Africa 10: 34–352, Pretoria.

Maré, G.S. (1932). 'Feeding cactus to sheep in times of drought'. Farming. S. Africa, 6: 462–2, Pretoria.

Maré, G.S. (1935). 'Spineless cactus and old man saltbush as grazing for sheep'. Farming S. Africa, 10: 371. Pretoria.

Maymone, B., Malossini, f. (1961). 'Digeribilità e valore nutritivo di cladodi e del frutto del Opuntia ficus indica'. Mill. impiegati nell'alimentazione animale. Ann. Dell'Esperim. Agric., XV, 2: 251–280. Rome.

McGinnies, W.G. (1972). 'North America'. In: McKell, Blaisdell and Goodin (eds) Wildland shrubs, their biology and utilization. USDA Forest. Gen. Techn. Rep. INT-1. Inter-mountain Forest and Range exp. stn., Ogden, Utah.

McKell, C.M., Blaisedell, J.M. and Goodin, J.R. eds (1972). Wildland shrubs their biology and utilization. USDA Forest Service, Gen. Techn. Rep. INT-1.

McKell, C.M., Malechek, J.C. (1978). 'The role of shrubs and trees in the management of natural grazing lands, with particular reference to protein production'. Supporting paper, item no. 10, 8th World Forestry Congress, Jakarta.

Monjauze, A.; Le Houérou, H.N. (1965). 'Le rôle des Opuntia dans l'économie agricole Nord Africaine'. Bull. Ec. Nat. Sup. Agric. 8–9: 85–164, Tunis.

National Academy of Sciences (1975). Under exploited tropical plants with promising economic value. Nat. Ac. Sces, Washington D.C.

Nechaeva, N.T., Prikhodo, S.Ya. (1968). 'Sown winter ranges in the foothill deserts of Soviet Central Asia'. Bot. Inst. of the Academy of Sciences of the Turkemn Republic English translation by Israel program for Scientific translation, Jerusalem.

Nemati, M. (1978). 'The role of shrubs and trees in the management of natural grazing lands, with particular reference to protein production'. Mimeo. Supporting paper, item no. 10, 8th World Forestry Congress, Jakarta.

Orev., Y. (1972). 'Demonstration of a shrub seeding method'. In: McKell, Blaisdell and Goodin (eds) Wild land shrubs, their biology and utilization. USDA Forest Serv., Gen. Techn. Rep. INT-1.

Papanastasis, V. (1977). 'Conversion of Quercus coccifera bush lands to grasslands in Greece'. Mimeo, Range Management Section, for. Res. Fust., Min. of Agric., Thessaloniki.

Peyre de Fabrégues, B. (1966). 'Les cactées fourragéres dans le Nord-est Brésilient'. Maisons-Alfort, IEMVT

Plummer, A.P. (1972).'Selection in Wildland shrubs; their biology and utilization'. Intermountain Forest and Range Exp. Stn., Ogden Utah USDA Forest Serv., Gen. Techn., Rep. INT-1.

Pratt, D.J. Gwynne, M.D. (1977). 'Rangeland management and ecology in East Africa'. London, Hodder and Stoughton.

Rojas, P.M., Malo, F.J., Palomo, P.G. (1966). 'El nopal forrajero en Nuevo Leon Agronomia'. 108: 34–39, Monterrey, Mexico.

Sarson, M., El Hamrouni, A. (1974). 'Valeur alimentaire de certaines plantes spontánées ou introduites en Tunisie'. Note de Recherche no. 2, Inst. Nat. Rech. Forest., Tunis.

Sarson, M., El Hamrouni, a. (1975). 'Appétabilité de certains Atriplex spontanés ou introduits en Tunisie).'Note de Recherche no. 8, Inst. Nat. Rech. Forest., Tunis.

Sarson, M., El Hamrouni, A. (1976). 'Résultats d'un essai de charge sur une parcelle de Medicago arborea L.'. Note de Recherche no. 14, Inst. Nat. Rech. Forest., Tunis.

Sarson, M., Salmon, P. (1978). 'Rôle des arbres et arbustes fourragers dans l'aménagement des pâturages Naturels en Afrique du Nord'. Mimeo. Supporting paper, Item no. 10, 8th World Forestry Congress, Jakarta.

Savory, R., Beale, C.I.A. (1974). 'Commercial Leucaena meal production in Malawi'. Mimeo, UNDP/FAO, MLW 71/ 519, Malawi Teheran.

Soriano, A. (1972). 'South America'. In: McKell, Blaisdell and Goodin (eds). Wildland shrubs, their biology and utilization. USDA Forest Serv. Gen. Techn. Rep. INT-1.

Theriez, M. (1966). 'Recherches sur la digestibilité de Opuntia ficus indica f. inermis en Tunisie'. Doc. Techn. Inst. Nat. Rech. Agro., Tunis.

Vassal, J. 61972). 'Apport des recherches ontogénétiques et séminologiqués à l'étude taxonomique et phylogénétique du genre Aciacia'. Trav. Lab. Forestier de Toulouse. D.Sc. thesis, Faculté des Sciences Toulouse.

Vietmeyer, N., Cottom, B. (1977). 'Leucaena promising forage and tree crop for the tropics'. Nat. Acad. of Sces, Washington, D.C.

Wickens, C.E. (1969). 'A study of Acacia albida Del. (Mimosoideae)'. Kew Bull., 23: 181–202.

Wilson, A.D. (1974). 'Nutrition of sheep and cattle in Australian arid areas'. In: Wilson A.D. (ed.) Studies of the Australian Arid Zone, II Animal production. CSIRO, Div. of Land Res. Mgt, Perth.

Wilson, A.D. (1977). 'The digestibility and voluntary intake of the leaves of trees and shrubs by sheep and goats'. Austr. J. of Agric. Res. 28: 510–508

Woodward, T.E., Turner, W.F., Griffiths, P. (1915). 'Prickly pear as a feed for dairy cows). `J. of Agric. Res., IV, 5: 405–450, Washington D.C.

Previous PageTop Of PageNext Page